An eductor is a simple version of a pump used to move a liquid form of a fluid out of a certain place.

However, unlike more complex versions of pumps, they do not have any mechanised components or moving parts that create an external force to transport a certain quantity of water. Instead, they rely on the simple theory of Bernoulli’s principle and a specific case of this, the Venturi effect.

What is Bernoulli’s principle?

As we know from the classical theory of fluid mechanics, Bernoulli’s principle states that a change in fluid velocity is marked within any system due to the pressure differential of the incompressible fluid or any change in the potential energy.

A Venturi effect is a specific case of this principle wherein there is a reduction or drop in fluid pressure and a consequential gain in the fluid velocity (from the fundamentals of fluid continuity) when it passes through a reduced cross-sectional area or a partial obstruction in its flow path.

In other words, any change in speed that a volume of fluid (and a resultant increase in kinetic energy) may attain while passing through changing cross-sectional areas in its path amounts to a proportional drop in static pressure head.

A venturi meter is a demonstrative representation of this effect. In it, a fluid is made to pass through a certain tube that is tapered midway, resulting in a decreased cross-sectional area. This changing area increases the fluid’s velocity and kinetic energy, accompanied by a sudden decrease in static pressure reflected in the water columns, as shown in the standard arrangement below.

Eductors use this principle, making them known as jet pumps. They essentially use the suction effect that arises due to the pressure drop stemming from Venturi action and, in turn, help strip off or transfer fluid from another source into another location.

The working of an eductor is pretty simple. A driving or motive incompressible fluid is made to enter through a tapering inlet nozzle. This fluid is drawn from another pump or a flow source.

When the fluid exits this nozzle, owing to the decreased cross-section and consequential rise in flow velocity, there is a decrease in pressure. This low-pressure, high-velocity fluid enters into another chamber. Now, in the wake of the low-pressure zone created by the fluid, the subject or other body of fluid is drawn in from another inlet opening into the system. For the suction fluid to be drawn in, the pressure created in the wake of the driving fluid has to be lower than this.

Energy transfer occurs as these two fluids get mixed up in the throat section. The suction fluid gets entrained into the driving fluid and gains kinetic energy. The mixture gets transferred to the diffuser section, where the area increases again. The resultant velocity decreases, and the pressure energy increases again. The resultant fluid now gets ejected at a definite outlet.

For all practical purposes, the suction and driver fluid in the eductor’s areas of application are mostly the same: water.

Eductors are used in ships for a variety of purposes. Some of them are:

• Stripping cargo oil tanks while loading/unloading operations
• Removing sludge from tanks like fuel oil, lube, or dirty oil tanks.
• Dewatering of cargo types like coal, sand, cement, stone, etc.
• Cleaning of various spaces in the vessel, ballast tanks, and draining deck areas in events of water accumulation.

In ships, eductors are continuously operated at higher pressures as desired.

One very important practice that needs to be kept in mind during shop operations is that the valves and screws from the suction line need to be opened only after the driving or motive fluid line is started. This is to prevent accidental flow of driving fluid into the tankage or other spaces from where the liquid is required to be sucked.

Moreover, if, on some occasions, the driving pressure falls below a certain level, the valves near the suction area lines need to be closed to prevent the flow of the driving fluid in the other area, as this creates a problem.

For example, when you intend to strip or drain an oil tank with an eductor, if the driving fluid, water, operates at a lower pressure and backflows into the tank, it gets mixed further with the oil or sludge content.

However, for all practical purposes, the valves and stoppers in the suction line are kept mostly open, as even when the suction fluid has reduced inflow velocity, it goes back to its source. It can be re-drawn back again after necessary pressure adjustments to the eductor. But if the backflow of this line is stopped during high-flow rate operations, there is a chance of excess pressure build-up and the eductor collapsing or bursting.

For all practical purposes, the drained contents from the eductor during tank stripping operations are collected into sludge or slop tanks, where they are discharged at very high rates through electrically driven pumps. During operations like deck de-flooding, the eductor outlet is connected directly to a discharge line from where it is drained into the sea.

You might also like to read-

• Understanding Water Jet Propulsion – Working Principle, Design And Advantages
• Selective Catalytic Reduction (SCR) Reactors For Ships – Types, Working Principle, Advantages And Disadvantages
• Understanding the Principles of Passage Planning
• Understanding Marine Sextant – Principle, Readings and Maintenance

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

What is Eductor On a Ship? appeared first on Marine Insight - The Maritime Industry Guide

The available sea depth, the distance from the mean water level to the seafloor, is often an essential parameter for consideration. For navigation of vessels (refer to the article on underwater keel clearance), fishing, oil explorations, rigging, research, and various purposes, estimating the depth of the ocean bottom is indispensable.

An echo sounder is a system that helps understand what is underneath and has been used by most seagoing ships for a long time. This system, which is one of the simplest applications of the Sonar (sound navigation and ranging) technique, uses the fundamental principle of acoustics to assess how much depth of water is available.

The theory behind this technique relies on the physics of underwater sound propagation and works by emanating sound/acoustic signals or pulses that rebound whenever they encounter an obstacle (like the seafloor) and travel back or echo again, giving us an idea about the time taken.

After that, from the first principles, with the help of the known velocity of sound waves and the recorded time, the depth of the water, that is, the linear distance from the mean sea level to the seabed level, can be approximated. While approximated is a more appropriate word for older versions of this technique, modern technologies for echo sounders are highly precise and reduce room for errors or inaccuracies.

Besides finding underwater clearance, echo sounders are also extensively used for purposes like finding shoals of fish, underwater explorations, etc.

Working of an Echosounder and Understanding Its Basic Components 

The main components of an echo sounder unit are 1) Transmitter, 2) Transducer, 3) Receiver, and 4) Display.

The transmitter generates short pulses of electrical AC signals from a voltage source directed towards a transducer, often through suitable power amplifiers that expand low-power signals to high-power.

The transducer, in this context, is a converter cum projector device that converts the electrical energy of the signals from the transmitter and emits them underwater.

These acoustic waves, emitted from the transducer unit, mainly located near the bottom of the ship hull, travel through the water, strike the seafloor, and ricochet back upwards. These reflected sound waves are then captured by the transducer, converted to electrical energy, amplified, and recorded by the receiver unit.

At this juncture, it is essential to note that the transducer unit serves two critical tasks:

i) An emitter and receiver unit that sends and receives sound wave signals to and from the vessel (or any other structure of interest)

ii) a converter unit that converts the input electrical energy to output acoustic or sound wave energy during transmission and converts the acoustic energy from the echo signals back to electrical signals during reception.

When the transducer transmits acoustic signals, it is often similar to a projector or speaker unit. While it receives the echo signals, it is analogous to a microphone or hydrophone unit.

During the transmission process, the input is essentially electric, and the output is acoustic, conversely, during reception, the input signals are acoustic or noise and output signals back along the reverse circuit are electrical waves again.

Some Time Base equipment records the time from beginning to end and is feedback-connected to the other significant components of the echo sounder system, helping estimate the distance. Moreover, in conjunction with the transmitter, they also control the pulse rate at which the signals or wave trains are generated.

Furthermore, as for the sound pulses both during emission and transmission to and from the seafloor, there can be a wide range of factors like losses, white noise, and various external disturbances. There are amplifiers along the circuitry that increase the amplitude of the electrical energy waves such that they can be well decoded.

The receiver unit reads the various parameters from the converted electrical pulse signals like amplitude, frequency, duration, etc. and computes the depth of the seabed using the simple relation:

Distance (d) = Velocity (v) X Time (t)/2

Here, the denominator, 2, takes care of the two-way transmission of the acoustic waves underwater (from ship to seabed and vice-versa), and t marks the total time taken. The calculated data is then displayed on the display unit for usage.

For all practical purposes, the speed of a normal sound wave in water is about 1500 m/s. However, this value may vary due to various factors ranging from weather to sea states, extreme salinity levels to extreme temperatures, and so on. Most modern vessels have means to take care of these errors and differences and accordingly account for water depth estimation.

In age-old methods, the calculation for estimating the depth was done manually based on the known velocity v and the recorded time interval between the emitted and recovered signal waves. Thereafter, devices like echo integrators were compounded to the sounding units to calculate the data and feed them to the display units for reference. Modern technologies include superfast and super-easy integrated digital systems that carry out the computations in no time and with full precision.

Echo-sounding can be of two kinds:

1) Single Beam and

2) multi-beam.

In simplest terms, single beams emit one particular beam of acoustic signals and cater for a smaller scope of area in determining the draft. Multi-beams, on the other hand, are more advanced systems that cover a wider range of area and use complicated wave mechanics like beamforming to have a better view of bathymetric distribution over larger swathes of seafloor area. We omit to discuss these in detail.

For all practical purposes, echo sounders emit acoustic signals in a conical manner, that is, divergent waves which spread over a certain area.

Though the values depend on the requirement, echo sounders must send short pulses (less than 10 milliseconds). Interestingly, the frequency of the wave signals also depends on water depth. Lower values within 20-25 kHz are used for deep waters, and shallower waters, higher order frequencies like 300-400 kHz or more are used.

You might also like to read-

• A Guide to Hydrographic Surveys
• Mastering Ship’s Navigation – Part 2
• What Is Deep Water Recovery?

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

What is an EchoSounder? appeared first on Marine Insight - The Maritime Industry Guide

Water sampling? The crew can do it themselves with Normec MTS’ sample kits

Fleet owners and shipowners encounter various regulations concerning safety and the environment, including those related to different types of water on board. While this may not be their core business, ensuring ships are compliant with laws and regulations is crucial. Normec MTS (Maritime Testing Services) has devised a user-friendly and efficient method for sampling water on board: practical sample kits that allow the crew to take water samples themselves.

World’s first with this approach

Hans van der Wart MSc, MBA, Director of Normec MTS, explains how the company came up with this method: “Previously, it was customary for someone to come on board to conduct sampling. This takes time, costs money, and scheduling is always on very short notice.

Moreover, there aren’t always employees available to do this. So, we thought: why not let the crew take these water samples themselves? We then analyse the samples in our laboratory. Legislation does not state that the crew cannot take the samples themselves.

We have included a manual in our sample kits, allowing them to sample everything at their convenience and according to the standards and guidelines in force. They can take ballast water samples when in port and scrubber water samples on the open sea, when the engine is running at full power.

Dedicated sample kits are also available for drinking water, grey water, and black water. As far as I know, we are the first in the world with this approach.”

Normec MTS sends out the sample kits worldwide, usually through the agents of the fleet owners. They deliver the sample kits to their warehouses and send them with the supply shipments to the ships. If a sample kit is urgently needed somewhere, it can be delivered anywhere in the world within a few days.

All data readily available for VGP and D-2

The ballast water sample kit has been developed for ballast water treatment systems with active chlorine, UV, and filtration applications, and includes a wide range of chemical and microbiological tests. The drinking water sample kit undergoes chemical and bacteriological analysis in the laboratory. The scrubber water sample kit is intended for the three mandatory samples per ship per year: inlet, outlet, and overboard discharge.

Normec MTS clients can log in to the client portal and view the complete history of all reports about their ships. Van der Wart says, “They can easily export this information if they need to upload this data somewhere to comply with legal guidelines. This saves a lot of time and effort and also prevents errors from manual entry. Consider, for example, the Vessel General Permit, the VGP.

Every ship operating in United States territorial waters must comply with this these regulations. You have to prove it, or you won’t get in. The data we provide based on the tests is already formatted to be uploaded via the Central Data Exchange of the Environmental Protection Agency, making the data available to the EPA with a few clicks.”

Another guideline that ships must comply with is the D-2 standard for ballast water treatment systems. These systems must be approved and then checked by an approved supplier. Normec MTS is an approved supplier and can test ballast water for microbiological contaminants.

Environmentally friendly legionella control

Environmental protection and safety are always the focal points for Normec MTS’s activities, as Van der Wart explains: “Consider bilge water, for example. We all do our best to prevent oil from getting into the seawater. But also, to prevent legionella problems in the onboard drinking water system.”

In this regard, Normec MTS expects to launch a revolutionary new method for legionella control soon. Van der Wart says, “We have developed an environmentally friendly method to combat legionella. Right after the water maker, we have installed a high-frequency unit that inhibits the growth of bacteria through vibrations. Ships no longer need to stay at the dock for chemical cleaning; they can let this system work on the go. The pilot study results are promising, so we hope to have more to report on this soon.”

About Normec MTS

Normec MTS (Maritime Testing Services) is an independent agency accredited by the Dutch Accreditation Council, equipped with all the necessary expertise for testing water on board. Normec MTS has multiple NEN-EN-ISO/IEC 17025:2017 accredited laboratories and the required knowledge of all applicable (inter)national laws and regulations regarding compliance and safety of water on board. Moreover, Normec MTS is an approved supplier for D-2 commissioning. By using smart ICT solutions, our clients benefit from our services in the best possible manner. Normec MTS is part of Normec, a leading organisation in the Testing, Inspection, Certification and Compliance industry. With over 4,000 employees, Normec works on a safe and healthy working and living environment. For this and future generations.

For more information, please visit https://normecmts.com.

Practical Sample Kits by Normec MTS Allow the Crew to Take Water Samples Themselves appeared first on Marine Insight - The Maritime Industry Guide

Bow thrusters are a type of propeller-shaped system fitted on the bow (forward part) and stern (known as stern thruster) of the ship. They are smaller in size than the ship’s propeller and help the vessel be more manoeuvrable at lower speeds.

Bow thrusters are generally used to manoeuvre the ship near coastal waters and channels or when entering or leaving a port during bad currents or adverse winds.

Bow thrusters help tugboats berth the ship to avoid unnecessary time and, eventually, money wastage because the vessel stayed less in the ports. The presence of bow thrusters on a vessel eradicates the need for two tugs while leaving and entering the port, thus saving more money.

Nowadays, ships have both bow and stern thrusters, which makes them independent of tugboats for manoeuvring in the port limits (if the port regulation does not make it compulsory to use tugboats).

Related Read: A Detailed Explanation of How a Ship is Manoeuvered to a Port

Installation Of Bow Thruster

Generally, side thrusters are transverse thrusters placed in a duct at the ship’s forward and aft end. The thruster set at the forward end is known as the bow thruster, and the one placed at the aft end is known as the stern thruster.

The requirement for the number of thrusters to be installed depends on the ship’s length and cargo capacity. The vessel’s route also plays an important factor as many countries have local regulations that stipulate the compulsory use of tugboats to enter or leave their port limits.

For the installation of the side thrusters, the following things are essential:

• The thruster compartment, also known as the bow thruster room, should be easily accessible from the open deck by the ship’s crew
• Most seagoing vessels use an electric motor for the thruster, which is heat-generating machinery and must, therefore, be positioned in a dry and well-ventilated area.
• The bow thruster room should have a high-level bilge alarm, and the indication should be provided in the engine control room and bridge.
• The thruster room should be well-lit
• The room should have at least one light from the emergency source.
• In the case of installation of more than one panel, make sure to operate the thruster from only one panel at a time.
• The thruster room should not be used to store flammable products in the area of the electric motor.
• The tunnel or conduit containing the propeller must be installed perpendicular to the ship’s axis in all directions.
• The propeller should not protrude out of the conduit
• Grid bars may or may not be fitted at both ends of the tunnel (taking into account how much debris the ship bottom will experience in its voyage). The number of bars for to be kept at a minimum as they tend to reduce the thrust force and overall performance of the bow thruster (or stern thruster)
• Sharp edges on the grid bars are to be avoided. A trapezoidal shape with no sharpness is a good choice of design for grid bars installed perpendicularly to the direction of the bow wave
• The design and position of the thruster tunnel should not interfere with the water flow under the hull or should not add to hull resistance
• Ensure that the material used for the installed thruster does not foul existing equipment inside the ship, such as steering links.

Related Read: Understanding Design Of Ship Propeller

Construction and Working of Bow Thrusters

The bow and stern thrusters are placed in the through-and-through tunnels on both sides of the ship. There are two such tunnels at the forward and aft ends of the ship.

The thruster takes suction from one side and throws it out at the other side of the vessel, thus moving the ship in the opposite direction. This can be operated in both directions, i.e. port to starboard and starboard to port.

The bow thrusters are placed below the ship’s waterline. For this reason, the bow thruster room should be checked for water accumulation at regular intervals.

The bow and stern thrusters can be electrically, hydraulically, or diesel-driven. However, the most commonly used are electric-driven thrusters, as in hydraulic-driven thrusters, there are many leakage problems.

Also, diesel-driven bow thrusters require more maintenance, and someone needs to go to the thruster room every time before starting to check the thrusters.

The thrusters used are usually of the CPP type, i.e., the blades on the propeller boss can be moved to change the direction of the thrust.

The boss, which carries the blades, is internally provided with a movable shaft (operated by hydraulic oil), also known as a Hydraulic Pod Motor-driven Thruster.

Once the signal to change the pitch is given, hydraulic oil will be supplied to operate the internal shaft (within the boss) to change the blade angle of the thruster (as shown in the video).

Related Read: 10 Precautions to Take Before Operating Controllable Pitch Propeller (CPP) on Ships

The motor shaft drives the thruster shaft via a pinion gear arrangement. The sealing gasket is provided in the motor casing which holds the water which is in the tunnel.

The Thruster assembly consists of the following components:

• The electric motor with safety relays
• The flexible coupling between the motor and thruster
• Mounting and casing for the electric motor
• The connecting flange and shaft
• Motor casing seal
• The tailpiece with shaft seal
• Bearings
• The propeller shaft
• The zinc anodes
• Grid with bars at both ends of the tunnel

Operation Of Bow Thruster

A bow thruster consists of an electric motor mounted directly over the thruster using a worm gear arrangement. The motor runs at a constant speed, and whenever a change is required in the thrust or direction, the controllable pitch blades are adjusted.

These blades are moved, and the pitch is changed with the help of hydraulic oil, which moves the hub on which the blades are mounted. As the thruster is of controllable pitch type, it can be run continuously, and when no thrust is required, the pitch can be made to zero.

The bridge controls the thruster, and the directions are given remotely. In remote failure, a manual method for changing the pitch is provided in the thruster room and can be operated from there.

Related Read: How Bow Thruster is Used for Maneuvering a Ship?

Usually, the hydraulic valve block, which controls the pitch of the blades, is operated in the BT room to change the blade angle in an emergency.

When the Bow Thruster is operated alone and the signal is given to operate the pitch at the port side, the thrust will turn the ship towards the starboard side from the forward part.

Similarly, when the Bow Thruster is operated alone, and the signal is given to run the pitch at starboard side, the thrust will result in turning the ship towards the port side from the forward part.

When the stern and bow thruster are operated together on the same side, the ship will move laterally towards the opposite side.

As seen in the above diagrams, the bow thruster and the stern thruster provide excellent manoeuvrability to the ship.

Things To Note While Operating Side Thrusters

• Ensure that the motor is started well ahead of the thruster operation and that the hydraulic lines are opened.
• Never operate the thruster beyond its rated load, else it may lead to tripping of the motor.
• Gradually increase the capacity and shift the pitch. Avoid sudden changes in the BT movement.
• The side thrusters are considered as an “on load” starting device, i.e. they should only be operated when they are submerged in water.
• Before operating the thruster, check for small craft, swimmers, boats and tugs adjacent to the thruster tunnel.
• Never touch any moving parts or the electric motor in operation
• In the case of installation of more than one panel, ensure the thruster is operated from only one panel at a time

Maintenance Of Bow Thrusters

1) The insulation must be checked regularly and kept dry. This is done because bow thrusters are not used frequently and thus there are chances of damages by moisture. Moreover, because of the frequent idle state of the bow thrusters, there can be a reduction in insulation resistance, especially in colder regions.

2) The space heater is checked for working condition so that the insulation can be kept dry.

Related Read: Importance of Insulation Resistance in Marine Electrical Systems

3) The bearings of the motor and the links are to be greased every month.

4) The condition of hydraulic oil is to be checked every month for water in oil and samples should be sent for lab analysis for further checking.

5) The thickness of the contactors is to be checked from time to time.

6) Checks are to be made for any water leakages in the bow thruster room which is an indication of seal leaking.

7) The flexible coupling between the motor and thruster should also be checked.

8) Check and inspect all the cable connections for cleanliness and tightness

9) Vacuum or blow clean the motor grid to remove the carbon grid, which may increase the operating temperature

Major Maintenance Of Bow Thrusters 

The major overhauling and maintenance of the bow and stern thrusters are done during the dry dock when the ship’s hull is out of the water, and the thruster blades and tunnel can be easily accessed.

Following maintenance is usually done in the dry docking:

• Replacement of the O’ rings and the sealing rings
• Removal of the pinion shaft
• Inspection and maintenance/ replacement of gear set
• Replacement of the bearings
• Repairs, cleaning and replacement of the blades
• Inspection of hub and repair if needed
• Inspection and overhauling of the oil distribution box (for operating propeller blades)

Advantages Of Using Bow Thrusters

1) Better manoeuvrability at low speeds of the ship.

2) Safety of the ship increases when berthing in bad weather.

3) Saves money due to the reduction of stay in port and less usage of tugboats.

Disadvantages Of Using Bow Thrusters

1) a huge induction motor is required, which takes a lot of current and load, and thus large generator capacity is required.

2) Initial investment is high

3) Maintenance and repairs are costly when there is damage.

The thrust force produced by the motor to move the ship will depend on various parameters, such as the hull design, power source, tunnel design, use of grids, draft and load of the vessel, etc.

The weather’s condition and the water’s state also play a vital role in BT performance.

You might also like to read:

• What’s The Importance Of Bulbous Bow Of Ships?
• How Bow Thruster is Used for Maneuvering a Ship?
• Bridge of a Ship- Design And Layout
• Nose Jobs For Ships – Reason Behind Retrofitting Bulbous Bow
• X Bow Hull Design vs Conventional Hull Design

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

The Essential Guide to Bow Thruster Construction and Functionality appeared first on Marine Insight - The Maritime Industry Guide

While most of the time, gigantic ships take our breath away with their sheer size, it is the engineering marvel behind them that makes them truly remarkable.

Propellers that move ships forth are of a size to bear the weight of such a huge ship. Hence, it’s only fair some credit be given to them and their size. Here is a list of the biggest ship propellers the marine world has seen.

1.  Emma Maersk

The marine propeller made by German company Mecklenburger Metallguss GmbH can easily be called the biggest marine propeller with its 131 tons weight.

Emma Maersk itself is the largest container ship around today. Justifiably so, it is the largest ship propeller ever built, providing the ship maximum speed of 27 knots. The engineering that went into making and ensuing sustenance of such a large propeller is certainly something to wonder about, along with its size.

2.  Hapag Lloyd owned a container vessel

This container vessel contains probably one of the largest ship propellers ever built. The six-bladed propeller is about 9.1 meters in diameter and weighs 101.5 tons.

Its height can be compared to the height of a three-storey building, making it easily contender for the biggest ship propellers in the world.

3. Oasis of the seas

Today’s biggest passenger ship also has one of the biggest ship propellers in the world.

ABB manufactured six-meter propellers to run the massive ship. The propellers are rotatable and provide greater manoeuvrability to the ship.

4.  Titanic

The Titanic was one of the biggest ships of its time. Proportionately, its propellers were just as huge, too. This passenger vessel featured three propellers.

These propellers measured 23 feet and 6 inches and weighed 38 tons each. The propellers were made of bronze. Each propeller was powered by a separate engine, creating a total power of 30,000 hp. It has been argued that the Titanic’s propellers were the largest ever to be built.

5.  Queen Elizabeth 2

QE 2 is another huge ship that flaunts huge propellers. It holds a pair of propellers, each 22 feet in diameter and weighing about 43 tons.

This makes them one of the largest ship propellers. The blades are specialized to provide propellers with a longer life. This ship carries spare blades on its foredecks all the time.

6. Palmer

The Antarctic icebreaker ship- Palmer flaunts a rather huge marine propeller. The ship holds two propellers, each about four meters long with four blades.

The propellers have been made from a sturdy alloy to give them extra strength. Norway manufacturers have pulled a feat with these propellers that can provide the ship with a speed of even three knots in thick ice cover.

7. Elation

This carnival cruise features one of the biggest ship propellers in the marine industry.

The Azipod propulsion system is just as efficient as it is gigantic.

8.  Bismark

Bismark was one of the most important German battleships launched in 1939. One of the reasons making it so important was its propulsion system that included three propellers, each 4.7 meters in size.

These propellers were huge structures made of manganese bronze alloy. These huge propellers could move at a speed of 270 revolutions per minute and displace a volume of 2.4 cubic meters per revolution.

References darkroastedblend , oasisoftheseas , titanicstation , qe2 , usap , bismarck-class

8 Biggest Ship Propellers in the World appeared first on Marine Insight - The Maritime Industry Guide

I still remember the day when I joined my maiden vessel more than a decade ago. A Supramax bulk carrier with the least automation and the most troubles. I was welcomed by a lot of judgemental yet uncaring eyes.

A new Cadet is on board! To add some spice to it, he’s a first-timer and presumably stupid; An old and tough Soviet Chief Officer who’s pissed because he couldn’t sign off in the last port.

Rain poured down the sky, and the day couldn’t get gloomier beyond imagination. I was shown my cabin and asked to change and to report immediately to the Training officer, who didn’t give a damn about who or where the trainee was. Without looking at me, he asked me to take the sounding of the tanks using a sounding rod tied to a rope, already drenched in the water. If a nightmare is a reality, this is it. With no one to supervise or demonstrate, I somehow could give the approximate sounding of the ballast tank I was asked to check. 

Next, after the sounding,  “Go do the line setting of the Forepeak tank in the Engine room”. Setting the lines was a far-off fantasy, and I didn’t even know the way to the Engine Room. Yeah, those were the days, and such were the challenges in those days. Yes, if you ask today’s Chief officers who were cadets or junior officers, then they would undoubtedly say, “Those were the days”. The primary concern in port operations was Cargo, and the junior officers and cadets would take care of the Ballast operations (mostly). 

Today, as a Chief officer and the Ballast water management officer, I face other distinct challenges if we talk about Ballast operations. 

It isn’t the case that we didn’t think about the environment back then. To prevent the transfer or introduction of pathogens or aquatic organisms from the source port State to the destination port State, IMO laid down guidelines for the implementation of Ballast water management and Sediment control on board ships in the form of the International Convention for the Control and Management of Ship’s Ballast Water and Sediments (BWM Convention), which was adopted in 2004 and entered into force on 8th Sept 2017. The purpose of the Ballast Water management system is to minimise the risk of transplanting harmful aquatic organisms and pathogens from the ship’s ballast water and associated sediments. 

Ways to Compy With Ballast Water Regulations

There are broadly two ways in which we can comply with the regulations.

First is the conventional Ballast Water exchange, and the other is the Ballast Water treatment system. 

The former has been in practice through ages and is carried out in three ways: 

1. Sequential method 
2. Flow Through method
3. Dilution method 

The Ballast Water Convention requires that the vessel should conduct ballast water exchange :

At least 200 nm from the nearest land and in water at least 200m in depth; if this is not possible, then as far as possible from the nearest land, and in all cases, at least 50nm from the nearest land and in water at least 200m in depth, or sea areas designated by the port state.

The standards mentioned above are categorised in the D-1 Standard of Ballast Water Management.

Now let’s talk about the elephant in the room, the Ballast Water Treatment system. 

As per the regulations laid down in the BWM Convention, 

Any type of approved ballast water treatment system shall discharge :

Capacity discharge for organisms:

1. < 10 viable cells/m3 for plankton < 50 μm
2. < 10 viable cells/mL for plankton between 10-50 μm
3. < 10 Colony Forming Unit/ 100 mL for Toxicogenic Vibrio cholerae
4. < 250 Colony Forming Unit/100 mL for Escherichia Coli
5. < 100 Colony Forming Unit/100 mL for Intestinal Enterococci

BWTS must have a type approval certificate and must be approved by the Administration.

The aforementioned standards constitute the D-2 Standard of Ballast Water Management.

So, the ships with the Ballast Water Management system complying with both the D-1 and D-2 standards can carry out the Ballast Water Exchange and can also use the Ballast Water Treatment system. On the other hand, if a ship complies only with the D-2 standards, she can only use the BWTS for ballast operations and is therefore not allowed to carry out Ballast Water Exchange. 

However, there are a few exceptions ( Such as the Safety of the Ship in Emergency situations, Accidental discharge, for the purpose of avoiding pollution incidents, etc.)  

A water filter is normally used in conjunction with another method, such as the ones discussed below. First, filters help to remove sediment, which can be taken in at turbulent ports and, if not properly removed, can accumulate in the ballast tanks. Also, a filter can remove a substantial portion of the micro-organisms. This reduces the time and energy required to neutralise the organisms that may enter through the filter and therefore need to be treated before the water they live in can be stored on board or dumped.

7 types of filtration processes used around the world 

• UV Systems
• Chemical Treatment
• Ultrasonic or Cavitation Treatment
• Magnetic Field Treatment
• Deoxygenation
• Heat Treatment.
• Electric Pulse and Pulse Plasma Treatments

The most widely used methods are the UV system, the Chemical treatment system and the Ultrasonic system. I have only encountered the UV system BWTS, and the ones who have seen the other systems vouch for the fact that the UV system is one of the most effective and hassle-free systems to be used. We’ll discuss the UV BWTS system further.

CONCERNS regarding the BWTS systems  

The first and foremost concern which I personally feel as a seafarer and the Ballast Water Management Officer is that when any regulation is formulated and enforced by the IMO or other concerned Organization, does it take into consideration the factors which are not in the control of the entities directly affected by that regulation or convention. For e.g., We as seafarers are duty-bound to comply fully with the provisions of the Ballast Water Management System but is the Port State in which the vessel is operating in any way accountable for the fulfilment of that regulation?

 Ignoring for a while the issues faced because of the substandard quality of the components of the BWTS system or the untimely breakdown of the BWTS system, the exposure of the vessel to the heavily turbid or muddy waters in the port where the vessel is berthed is a major issue. As a Chief officer, my primary concern is whether I would be able to ballast even half of the quantity I’ve planned to.

 And if you push it further and stress the system, the filter gets choked ( in one case, the filter element suffered serious damage ), and the system gives away. Time in such cases becomes crucial because stoppage of the cargo operations from the vessel’s side for ballast operations can create a lot of ruckus, commercial losses and intense cross-questioning from the stakeholders. 

The eventual decision that can be taken in such conditions is to take dispensation from the Flag State and, provided the Flag State approves, ballast the tanks with the muddy water and later carry out the Ballast Water Exchange or deballast to the shore reception facilities if in case the terminal accepts that.

This will mainly be required if the vessel unloads the cargo in a single port. Suppose in case the ship is partly unloading cargo and would require minimum or no ballast and already has some ballast water in her tanks. In that case, the ship might consider doing the internal transfer of the existing treated ballast water to correct the list/trim for the cargo operations, depart after carrying out the operations, and when in the open sea or a relatively clean source of water, take in the required quantity of ballast. 

Moreover, the company might not always be punctual and efficient in the supply of spares or replacement parts. Notwithstanding the fact that the makers might take a lot of time supplying the ordered part, these parts are costly, and the company doesn’t always supply you with everything you ask for. A part was ordered before I joined that particular vessel, and the part was not received even after I signed off from that vessel. So, the readers are left to the imagination here. 

Another major issue which I faced was the overheating of the Ballast sensor panels and circuits in the BWTS room, especially in the relatively warmer / hot regions of the world. Irrespective of the fact that the ventilation/cooling/exhaust fans are provided in the panels, they are rendered ineffective in such a hot climate. 

This leads to repeated alarms in the BWTS system and subsequent breakdown/trip of the BWTS system. The thing that can be done in such cases is to deploy an intrinsically safe (on tankers especially) portable fan in the BWTS room and open all the doors/hatches/vents/openings of the BWTS room for proper ventilation. Well, the other thing that can be done is to pray that your BWTS system copes up. 

Damaged Filter element

On the flip side, you can’t bypass the system because then you’d be deemed to be going against the regulations. We’re left with limited choices and immense stress and pressure in such situations, and then I wonder, did the IMO even take the muddy water into consideration before drafting the relevant regulation? We’re duty-bound to comply with the regulations in whatsoever conditions (except in life-threatening situations and emergencies), and the conditions which might totally turn against us.

Muddy Water

The problems frequently faced during the BWTS systems include, but are not limited to : 

1. Panel overheating ;
2. Frequent failing of UV Lamps ;
3. Leakage of water in the UV Lamps sleeve ;
4. Filter clogging ;
5. Failure to cope in turbid waters ;
6. Software failure, rendering the system not to start;
7. Failure of automatic valves ;
8. Sensor failure ;

The consequence of a treatment system failing to perform as anticipated is a regulatory violation picked up by Port State control (PSC) during an inspection. The penalisation depends on the jurisdiction, but the expected outcome could be PSC deficiencies, detentions and financial penalties.

Even giants such as Intertanko and ABS have acknowledged that Operational problems continue with Ballast Water Treatment Systems. The degree of operational challenges with BWTS fitted by tanker owners (mostly retrofit) was revealed by Intertanko at a forum in Singapore. The feedback from the members was that in their assessment, 60% – 80% of systems did not work correctly. 

Consequently, today a part of me puts more focus on the BWTS operation than the Cargo operation, majorly because the former has become more challenging in the port operations. The failure of the BWTS system in critical stages could be nerve-wracking. On a candid note, the BWTS system gives me and the electrician sleepless nights. On a serious note, compliance with the Rest hours has become a myth. Never had I  imagined that there would come a day when we would need to treat the Ballast water. Inevitably, the day came and came with a lot of concerns.  

You might also like to read-

• What is Ballast Water Management Plan?
• What is Ballasting and De-ballasting?
• Major Problems Faced During Ship’s Ballasting And De-ballasting Operations
• What is Ship Oil Pollution Emergency Plan (SOPEP)?

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

Ballast Water Treatment System – A Boon For Many, A Menace For Some appeared first on Marine Insight - The Maritime Industry Guide

Every seafarer is familiar with the term bunkering and has either participated in or at least seen the operation of bunkering whilst he or she is on board. They may have also seen samples collected from the bunker manifold through drip sampling. Taking four samples is the norm, 1 for the supplier, 1 for MARPOL, 1 for the ship and 1 for lab analysis.

Shipping companies have a tie-up with bunker sample analysing labs, and the labs provide ships with a sampling kit. Using the kit, samples are collected and sent to the laboratory for testing. Most of the time, only heavy fuel oil samples are sent to shore for analysis, but I have also seen on a couple of ships where we were sending MGO samples. The sample analysis is sent back to the ship in about 3-4 days.

When I was a junior engineer and even up to fourth I never really paid much attention to the lab analysis. I used to check the density of the fuel to adjust the gravity disc of my purifiers accordingly. But there is a lot more to these analyses than just that. A lot of problems are created, because of improper treatment of fuel, and these can be avoided by paying attention to the lab analysis.

Given below are 10 points marine engineers must check in the fuel oil testing report.

Density: The supplier, on completion of bunkering, gives a BDN( bunker delivery note), which has the density mentioned on it, but this is basically to determine the weight of fuel delivered, it might not be very accurate. The correct density is required for changing the gravity disc of the purifiers, to ensure correct purification. This is not required in the newer purification systems as they do not have a gravity disc.

Viscosity: HFO used to burn in marine engines has a viscosity of 380 cst, and for IFO it’s 180cst(This is at 50 deg centigrade). Generally, the viscosity required for combustion is between 13-15cst. But it can be different for different engines. In most ships, the viscotherm is automated, which means it continuously monitors the viscosity of the fuel going to the engine and accordingly regulates the temperature. However, in older ships, the viscosity is regulated manually, and in such cases, it is required to know the right temp to maintain viscosity. Most labs give a chart which will show different temperatures for different viscosity.

Water %: Fuel with high water content will burn less efficiently as the calorific value is reduced. The high amount of water in fuel is quite troublesome if the fuel is going to be kept for a long time in a bunker tank. Over a period of time, the water will settle at the bottom and cause problems while transferring. It would be good to start heating right from the start after bunkering, also when it is in the settling tank, it has to be drained very often. Also, be ready for sludge tanks getting filled up.

Carbon residue: It is the amount of carbon remaining when the fuel sample is completely burnt. It indicates the quality of the fuel. A higher carbon residue value means more deposits on piston land and fuel valve tips. It also means fuel oil has poor ignition quality, which causes ignition delay after burning. Avoid low-load operation when using such fuel. Or if have to run on low load as most ships are now being run on lower rpm, the main engine is to be run at high load for at least 1 to 2 hours. Also, more emphasis on proper fuel treatment.

Sulphur content: The most important value to be checked, for MARPOL regulations, especially when sailing in ECA areas. As of 1^st January 2015, the sulphur content for fuel on ships sailing in the ECA area is 0.10% m/m. Also, it’s necessary to check sulphur content in the new intelligent engines, where the cylinder lubrication is done exactly as per the sulphur content of the fuel in use. High sulphur content leads to cold corrosion, so the jacket water temperature is to be maintained on the higher side, especially in standstill conditions.

Vanadium and Sodium %: Vanadium is a metallic element found in crude oil. When it combines with sodium in the ratio of 3:1, it forms a low melting point compound which causes high-temperature corrosion and the formation of localised hot spots. This leads to the burning away of exhaust valves, seats and piston crowns. Although removing vanadium is difficult, it’s easier to remove sodium via purification and heating.

Another method of reducing high-temperature corrosion is by keeping exhaust valves and seats cool, but again you cannot reduce jacket cooling water temperature too much, or it will lead to cold corrosion. Maintaining turbochargers and scavenge manifolds in good condition will help reduce the effects of high-temperature corrosion as it leads to better scavenging, so automatically, the cylinder remains cooler.

Aluminium and silicon%: These are more commonly known as catfines and are elements that remain in the fuel after catalytic cracking. These are tough small abrasive particles that are very difficult to remove. They can cause damage to the surfaces of the plunger and barrel of fuel pumps, cylinder liners and fuel valves. Their concentration can be reduced by running purifiers with very low throughput. Also, a high concentration of catfines means your auto backwash filter will get choked frequently. If your ship has a history of bunkering fuel with high catfines, once a year, it is better to drain and clean the fuel oil service tank thoroughly.

Flash point: The flash point of all fuels used in the engine room should have a flash point greater than or equal to 60. This information will be presented by the supplier before bunkering, but it is always better to confirm this from the lab analysis.

Pour point: The pour point is the minimum temperature at which a liquid ceases to flow. For pumping and handling purposes it is always good to know the minimum temperature to be maintained.

CCAI: Calculated carbon aromaticity index is an indication of the ignition quality of the fuel. Values above 870 are not recommended for most types of fuels.

Also, check if the fuel is compliant with the standards set as per ISO 8217

The above are the major points to be considered before using the newly bunkered fuel oil. In addition to this, labs may also conduct further additional tests such as total sediment, or for lead, phosphorous, calcium and zinc, which are indicators of the presence of waste lubricating oil, which sometimes may be added to the fuel.

A laboratory analysis is an excellent tool to give us an indication of the quality of fuel bunkered. Proper handling and treatment of fuel oil is not only good for the engine but also gives us peace of mind during a voyage.

Always keep all equipment involved in the transfer and handling of fuel in good condition. Auto backwash filters are to be cleaned regularly and never in any condition to be bypassed.

Thank you, and please feel free to add your valuable comments.

You might also like to read:

• What Are Bunker Ships?
• How To Reduce Bunker Spend Of Your Ships: 9 Important Points
• 15 Practical Tips For Bunkering and Storage of Fuel Oil On Ships
• The Ultimate Guide to Fuel Oil Bunkering Process on Ships
• Bunkering is Dangerous: Procedure for Bunkering Operation on a Ship

Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight

10 Things A Marine Engineer Should Check In A Lab Analysis Report Of Fuel Oil appeared first on Marine Insight - The Maritime Industry Guide

Cruise ships house thousands of passengers and crew, which leads to enormous wastewater generation of up to 1000 cubic metres per day. Hence, Wastewater management has become a critical aspect of everyday operations.

 A cruise ship needs to be self-reliant in this aspect, as it stays away from land for a considerable period of time. 

Wastewater onboard cruise ships are categorised into two types, namely, greywater & blackwater.

Greywater comes from bathrooms, showers and washbasins. The water from galleys, meat rooms, fish rooms and laundries is also greywater. However, such water is called galley & laundry grey water for ease of differentiation.

Blackwater is the dirty water from toilets and urinals, including flushed water. Since it consists of human waste, which is infectious & an environmental hazard, it needs special handling & treatment processes for its storage onboard or its discharge overboard outside ecological limits.

Therefore, our focus in this article will be on blackwater management, treatment and disposal.

Related reading:

• Sewage Treatment Plant on Ships Explained
• 4 Important Terms Related to Sewage Treatment Plant on Ships

Blackwater Collection & Segregation/Pre-treatment

Blackwater is collected in blackwater collecting units via a ring-main system. The ring-main system is divided by various decks or zones onboard and connected to different blackwater collecting units.

There can be multiple numbers of collecting units (4-10 units) depending upon the size of the ship. They are usually installed in technical spaces throughout the ship, where technical staff can monitor and maintain them.

The blackwater is collected in the collecting tanks by gravity or vacuum. In the case of a vacuum system, the vacuum is generated in the collecting tank & its suction line using attached vacuum pumps which operate per the vacuum level through sensors.

The blackwater goes to the collecting units through coarse strainers, which must be cleaned daily or as per demand. These strainers remove any large-sized solids that may go to the collecting tanks, clog pipework or the discharge pumps. 

The blackwater collecting units have attached discharge pumps that are normally set to work on a timer but can also be set to work on the level. The pumps are operated by float switches and operate from time to time to lower the level of the blackwater collecting units. These pumps are sewage discharge pumps and transfer the blackwater from the collecting units to screen presses.

The screen presses further separate the solids, such as toilet paper, plastics, grit, fibres, rags etc., from the blackwater, thus ensuring that only the liquid passes through to the next stage, which is the treatment stage. 

This is done by first separating the larger-sized solids by a mesh called a screen and, after that, removing the fine suspended solid impurities by a large screw shaft operated by a motor, which grinds and separates out the finer solids. 

The screened or filtered blackwater passes through to the next stage, the treatment stage, whereas the separated solids from the screen press are collected in a separate tank, usually known as a Bio-sludge tank.

Accommodated greywater can also be fed to the MBRs along with blackwater. This process is automatically controlled as per demand, with the help of a 3-way valve at the inlet to the screen presses. At times of low blackwater generation, which is usually at night when most people are asleep, the 3-way valve supplies greywater to the MBR system to maintain the levels of the stages.

In the above case, the accommodation greywater is stored in separate double-bottom tanks. MBR greywater pumps are provided, which operate automatically as per the greywater demand from the MBR and the level of greywater in the DB tanks.

Treatment Process

The screened/filtered blackwater goes to the sewage treatment plant known as MBR. MBR stands for Membrane Bio-Reactor. As the name suggests, it treats sewage or blackwater through biological processes and membrane filtration.

The MBR has two stages. The blackwater from the screen presses comes to the 1st stage, where aerobic bacteria treat it. A constant air supply generates aerobic bacteria through blowers and diffusers, which create air bubbles for evenly distributing the air throughout the biomass. Excess air, water vapour & gases are vented from both stages by attached vent lines to the atmosphere.

The aerobic bacteria act on the sewage, thus breaking it down & separating the sludge from the sewage water. The treated water now passes through to the 2nd stage of the MBR, through the ISFs, which stands for Inter-Stage Filters.

The ISFs help to remove any finer particles or impurities that may have been generated in the first stage or carried over from the pre-treatment stage. The filtrate from the ISF is collected in an attached filtrate tank, from where it is pumped to the 2nd stage of the MBR by filtrate pumps, whereas the separated screenings (solids) collected in the screenings tank and are either pumped back to the screen press or the 1st stage by the screening pumps. Both the filtrate & screenings pump has one operational pump & one standby pump.

The condition of the ISFs must be regularly checked, and the filters cleaned if required. The filtrate to screenings ratio is a parameter that indicates the health of the ISFs. Usually, the ratio should be between 1 and 5. Readings well outside this range will necessitate checks and/or adjustments.

Like in the 1st stage, further aerobic action also takes place in the 2nd stage. This is to ensure that sludge separation takes place as much as possible so that only liquid passes through to the membrane-filtration stage, thus reducing the possibility of membrane clogging and/or breakage, which can result in downtime and increased maintenance.

The separated sludge from both the 1st stage & 2nd stage must be removed daily to prevent the accidental carryover of the sludge along with the liquid to the membrane. There are separate sludge pumps and tanks which are provided for that purpose. Chemical dosing is also done in both stages for sewage sludge conditioning.

The liquid (wastewater) under treatment is pumped from the bioreactor’s 2nd stage to the membranes by the centrifugal crossflow pumps. The membranes are usually arranged in multiple (usually 3 to 4) parallel banks. Each bank has several membranes in series & its crossflow pump. The individual banks can be isolated for cleaning or maintenance without disturbing the process.

Each membrane is tubular, with 8 mm nominal bore tubes mounted onto 200 mm nominal diameter fibre-reinforced casings. The membranes are rated in the ultra-filtration range, with a nominal pore size of 40 nanometres. 

There are several billions of such microscopic pores on the surface of the membrane fibre, which while forming a barrier to microbial impurities such as bacteria, viruses and protozoa, allow pure water molecules to pass through, thus affecting treatment. The untreated wastewater recirculates back to the bioreactor 2nd stage.

The membrane banks, which foul due to accumulation of impurities, must be backflushed or flushed with clean freshwater once each day and chemically cleaned once a week for continued operational reliability and to avoid breakdown and damage to membranes. Membrane replacement can be a costly and time-taking affair.

The membrane-filtered liquid, known as permeate or treated wastewater, may be treated with chlorine for further disinfection before being pumped to permeate or treated wastewater storage tanks through a Turbidity sensor, which stops the permeate pump in case of high turbidity. 

The stored permeate is pumped overboard, if & when outside of environmental limits, by treated wastewater pumps. Chlorine treatment (disinfection), in the case of MBRs, is not usually necessary if the bio-reactor & membranes are performing well.

Weekly tests must be performed for Biological/Chemical Oxygen Demand, smell, colour and E-Coli by taking samples from both stages of the bio-reactors permeate to ascertain the performance of the MBR plant.

While accommodation greywater can be supplied to the MBR, it is not advisable to use galley & laundry greywater, as the presence of detergents and/or oils can potentially be detrimental to the aerobic bacteria, thereby affecting biomass generation and function. For this reason, galley and laundry greywater also have their own separate storage tanks.

Blackwater management is a complex process that demands a comprehensive understanding of the system, strict attention to parameters, adherence to proper & timely maintenance procedures and accurate troubleshooting for continued efficiency and operational continuity.

The system’s complexity can also be a factor in the size of the ship. Bigger ships will put a considerable load in terms of operations & routines. Although designed to operate automatically and without manual assistance, systems are always prone to failure. It is advisable to follow manufacturer guidelines, manuals, maintenance schedules & regular testing to ascertain the plant’s health. 

You might also like to read-

• The World Largest Cruise Line: Carnival Cruise Ships
• The Vista Class Queen Victoria Cruise Ship
• The Incredible MSC Fantasia Cruise Ship
• What are Polar Cruise Ships?

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

Blackwater Treatment Onboard Cruise Ships Explained appeared first on Marine Insight - The Maritime Industry Guide

As anyone working in the shipping industry will attest to, bunker (or fuel) is one of the biggest expense items for any container shipping company.

According to most estimates, bunker costs comprise circa 50% to 60% of a carrier’s total operating expense, thus making it by far the largest component of the carrier’s variable cost base.

Bunker prices consequently exert an inordinately higher influence on any shipping company’s cash flows and have the potential to make or mar its fortunes.

Matters are aggravated by the inherent volatility in bunker prices, which show violent fluctuations consequent to global geo-political tensions and are dependent on the actions of a cartel of oil-producing nations. These fluctuations in price make it difficult to estimate expenses and budget for forthcoming periods or set freight rates to reflect costs to a reasonable degree.

Apart from this, bunker, though proportionately tied to business volumes/ containers transported, is not a completely direct function thereof (as would be the case with Terminal Handling Charges, which are, in essence, the straightforward product of the THC quantum charged by the port/ terminal/ stevedore and the number of containers/ quantity of cargo handled), and is, therefore, an area where companies need to adopt a multi-pronged approach and resort to innovative strategies to reduce bunker consumption and overall bunker spend.

Over the past couple of decades, bunker prices have typically been on an upward trend, save a few years of global downturns and recessions, which meant that shipping companies were left staring at ever-increasing bunker spending, year after year.

As a consequence of the wafer-thin margins that the container shipping industry has historically experienced (prior to the super profits in 2021 and 2022 that can primarily be attributed to global supply chain disruptions, widespread port and quayside congestion, and Covid-induced lockdowns), as well as the cyclical nature of the industry, Carrier’s have focussed rigorously on reducing their cost base, with Bunker obviously being the prime area of attention, by virtue of it comprising over half of overall operating expenses.

It is for this reason that shipping companies are extremely particular about their bunker consumption and spending, expending considerable efforts to ensure optimisation of the bunker procurement process, as well as having in place a robust mechanism for monitoring and reducing consumption thereof.

In this article, we will explore the various tactics and methods adopted by shipping companies to reduce bunker consumption and overall bunker spending.

1. Slow steaming and Super-slow steaming

The concept of slow steaming essentially involves sailing the vessel at slower speeds to reduce bunker consumption. This is the most prevalent tactic used to regulate bunker consumption, as well as one of the most effective. Its effectiveness stems from the fact that the correlation between vessel sailing speed and bunker consumption is not a straight linear equation but rather a quadratic one, implying that as the vessel sails at slower speeds, the corresponding drag on the vessel decreases by an even greater magnitude.

In practical terms, this means that the quantity of bunker consumed decreases in greater proportion than decreases in speed, enabling commensurately higher savings through even a relatively slight reduction in sailing speed.

Studies conducted on the effectiveness of slow steaming have concluded that reducing speed from 27 knots to 18 knots reduces fuel consumption by as much as 59%.

Under slow steaming, a vessel that typically sails at an average speed of 20-24 knots will instead sail at a speed of around 18-20 knots.

A further extension of this tactic is super slow steaming, where the vessels sail at an even slower speed of below 18 knots.

A relatively sophisticated variant of this concept involves using slow steaming only in accordance with commercial considerations rather than being implemented as a standard policy.

Here, a vessel will sail at its normal speed on the head haul voyage (when it is laden with export containers from manufacturing-dominant hubs in Asia, bound for the major consumption centres and markets in Europe and North America, while on the backhaul leg (the return journey, when the vessel will carry a lower quantity of containers, most likely lower in value than was carried on the head-haul leg, or repatriate empty containers), the vessel will sail at a slower speed.

Slow steaming was first introduced in the mid-2000s when global trade and container shipping were experiencing a boom. With container volumes transported globally growing at a healthy rate, bunker prices too were rising sharply, resulting in carriers’ annual bunker bills increasing manifold.

Maersk Line was one of the pioneers, having introduced slow steaming on its major main haul trade routes, and the trend slowly caught on as other carriers, upon becoming cognisant of the potential cost savings, started to reduce sailing speeds to the point that it ultimately became a firmly entrenched industry practise.

The other advantage slow steaming offered was the absorption of excess shipping/ vessel capacity. With investments in bigger vessels and an increasing order book of new builds, the market was flush with shipping capacity, which soon outpaced the growth in demand. Utilisation rates plummeted, and carriers realised that they had more tonnage than could be gainfully deployed.

This challenge was partly offset by slow steaming, as with slow steaming, the voyage days increased, meaning that shipping companies had to deploy more vessels on the service/ trade lane to be able to offer weekly rotations and meet originally planned sailing schedules. Slow steaming thus offered the dual benefit of reduction in bunker expenses and also soaking up the surplus capacity.

An added benefit of slow steaming is that it is environment friendly, as the GHG emissions reduce significantly due to the lower quantity of bunker utilised.

2. Using alternate / optimal routes

The choice of routing impacts the level of bunker consumption in far more ways than is obvious.

Whilst Carriers typically would prefer the shorter route when planning their service network and sailing schedules, the distance involved, though the most obvious factor, is not the only parameter that determines the vessel route. A host of other factors are evaluated while determining the route, such as climatic conditions, tidal forces etc.

This is so because in rough seas or in adverse weather conditions, vessels need to burn more bunker to sail. Likewise, if a vessel sails with the flow of the tidal currents, they consume lesser fuel as compared to if it had been sailing against the force of the tide.

Carriers, therefore, try to set or revise proforma sailing schedules and align routes with favourable sailing conditions. This also includes checking weather forecasts for inclement weather conditions and rerouting the vessel as necessary.
Apart from this, there are commercial and operational considerations at play as well.

Carriers try to optimise bunker consumption by striking the right balance between transit speed and bunker consumption. This is done by ensuring that the vessel takes the shortest route while carrying export cargo on the head haul, which needs to reach destination markets in time.

On the backhaul leg, however, where the cargo is typically not time sensitive or involves repositioning of empty containers, speed is not of the essence, wherefore Carriers sail at slower speeds.

Another example is when carrying high-value and time-sensitive reefer cargo, where the revenue, costs and risks render sailing at faster speeds a more desirable option.

Yet another example involves the threat of piracy. When sailing through pirate-infested waters, vessels sail at faster speeds, necessitating greater bunker consumption.

Once again, this decision is also influenced by prevailing bunker price levels. In a low bunker rate environment, the Carrier might decide that the cost of the additional bunker consumed is more than recompensed by the additional revenue from having ships and container turnaround faster (by sailing faster to complete the round trip rotation in fewer days and thus making more voyages).

3. Using Route optimisation software / technological tools for optimising routes and overall planning

Over the past few years, a plethora of technological solutions have been developed, which aim to help Carriers with inter alia planning their voyages, determining optimal speed, using AIS to forecast weather conditions, etc., all of which are then used to determine that routing option and schedule which involves the least amount of bunker consumption.

Driven by the growing complexity of international trade and transport, these tools are rapidly gaining in popularity, especially with the growing usage of LSFO (necessary to comply with the latest IMO regulations regarding GHG emissions).

Carriers increasingly realise that investment in software can yield significant benefits in the form of reduced bunker expenses.

The latest example of a leading global container carrier is that of CMA-CGM, which has signed a Memorandum of Understanding with PSA to use PSA’s Opt-E-Arrival tool. The tool is designed to reduce bunker consumption by enabling JIT at ports, which is expected to reduce the idle time that vessels generally spend awaiting berths. It is conjectured that this will result in a reduction of bunker costs between 4% to 7% for vessels calling in Singapore.

4. Using scrubbers

Especially useful in a high bunker cost environment, using scrubbers ensures a quick return on investment/ faster breakeven and has the added benefit of widening bunker procurement scope (in terms of a greater number of bunker suppliers and bunkering locations).

Carriers have seen a massive increase in their bunker spending post the implementation of stringent rules relating to GHG emissions. The new regulations impose a cap of 0.1% sulphur emissions, which can be achieved either by using LSFO or installing scrubbers on vessels. Being a more refined version of the bunker, LSFO commands premium rates and is also not as widely available, causing the demand-supply mismatch to exert inflationary pressure on bunker prices.

In this scenario, a cost-effective option is to install scrubbers on vessels, post which vessels can continue running on HFO, which is considerably cheaper than LSFO.

Given the widening spread between prices of HFO and VLSFO (USD 332/ tonne in Rotterdam and USD 538/ tonne in Singapore in June 2022), it makes economic sense to install scrubbers on vessels, so it can continue using HFO grade bunker.

While the average cost of installing a scrubber on new builds is approximately USD 2 million (retrofits on existing vessels are even more expensive), considering the prevailing LSFO premium, many shipping companies have opted to equip their vessels with scrubbers.

The ICS estimated that even assuming average scrubber installation costs of USD 5 million a vessel, the CAPEX would be recovered in 2 to 3 years (perhaps even earlier, if the premium continues to increase at its current rate).

5. Bunker futures/derivatives

As with most commodities, Bunker fuel too has a fairly evolved derivative market, where Carriers can hedge their bunker requirements and try to maintain stability in bunker expenses.

It is, however, not as frequently used in shipping as it is in other transportation industries (for example, it is estimated that Airlines hedge upto 60% of their bunker requirements).

Looking at the specific segments within the shipping industry, the limited levels of trading bunker derivatives is typically restricted to bigger shipping companies, with the medium and smaller-sized companies almost exclusively relying on the spot market.

Carriers set freight rates basis their cost base, which also includes bunker costs. While Carriers can estimate bunker price levels to some extent, given the extreme volatility in bunker prices on account of the multitude of variables involved, Carriers are unwillingly compelled to assume the risk of bunker prices rising more than anticipated, in which case their budgets and balance sheets will be negatively impacted.

It is to mitigate such risks and ensure minimal deviation to business plans/ revenue and profit projections that Carriers adopt hedging strategies to maintain a steady flow of bunker supplies at budgeted average prices.

Given the historical trend where oil/ bunker prices have been in contango, it is a very reasonable assumption that the bullish trend will continue in future as well, wherefore Carriers can reduce bunker spending and also exposure thereto by using bunker derivatives.

The slow but steady adoption of bunker derivatives has encouraged companies to launch future contracts, with one such example being the oil price reporting agency Argus, which launched a marine fuels future contract for Singapore, listed with the Chicago Mercantile Exchange.

6. Using the right bunkering port and incorporating it into the voyage or sailing schedule

As with most commodities, the prices of bunkers vary depending on the location. Globally, there are a few major bunkering locations, primarily catering to their geographical regions, where the majority of ships traversing the region bunker up. Prominent bunkering locations include Singapore, Rotterdam, Hong Kong, Fujairah, Panama, etc., each of which is a recognised centre of global/ regional maritime trade.

It, however, often happens that for geo-political and economic reasons, some countries offer bunkers at lower prices to induce vessels to call at their ports to fuel up. The intent is generally to utilise their vast reserves of natural gas and earn precious foreign exchange in the process.

An example was the Far East Asian ports of Russia, where the bunker was cheaper than at the major bunkering locations, prompting many Carriers – especially those that operated Intra Asia services – to add Russian ports to their service schedules and refuel at those ports. The difference in the bunker was, to an extent, so as to make it viable for the Carrier to incorporate Russian ports in their schedules – despite lower quantities of export and import cargo.

7. Energy Efficient ship engines and ship structure/ design

Since vessels are typically designed to run at a certain speed, the vessel’s engine is so constructed as to operate efficiently at this speed. Thus, the engine design is a constraint in implementing the policy of slow steaming and can thus reduce anticipated bunker savings (or partially negate the savings through higher engine maintenance costs).
Since slow steaming is now the norm in the industry, most new vessels being ordered are designed for sailing at slower speeds, which helps greatly in reducing bunker consumption.

Another facet is the design of the ship’s hull, where innovations include a streamlined structure and bulbous bows.

8. Regular reporting and analysis of deviations between actual and planned consumption

Given that almost all modern commercial vessels are connected through the internet, there is a mass of data available on all aspects of operation, including bunker consumption.

Prior to a voyage/ launching of service, the shipping company estimates its profit from the service by estimating costs (including bunker) and the expected revenue.

The cost estimates for bunker are derived basis the expected bunker consumption, which in turn is calculated basis the route, distance, weather conditions, vessels fuel efficiency, cargo weight, etc.

Since this calculation is a fairly straightforward one and is based on historical data (fuel consumption on previous voyages) and known facts (such as cargo weight and distance), deviations from the budgeted bunker consumption would only be on account of contingencies or unforeseen circumstances; otherwise, the bunker consumption ought to be within the estimated range.

Carriers should have in place a system of reporting and analysis to monitor actual bunker consumption as opposed to budgeted bunker requirements and investigate in detail where there are unexplainable deviations of significant magnitude.

Such reporting and analysis processes should also include comparing with internal records, benchmarking against historical consumption for vessels of similar class, and competitors’ average bunker expenses.

Such analysis will not only help in controlling bunker expenditure but will also serve as a reference for future calculations, and learnings therefrom can be used to streamline bunker consumption even further.

Monitoring bunker consumption against established benchmarks also increases the probability of frauds being prevented or detected well in time.

9. Preventive policies and measures to avoid pilferage and fraud

Since bunker is very expensive, people involved in the bunker supply and procurement process often find it extremely lucrative to indulge in various malpractices, as even a small fraction of the overall bunker procured can be valued at significant amounts.

It is for this reason that the probability of malpractices being perpetuated in the bunker procurement process is quite high, ranging from instances of pilferage to large-scale fraud.

Common malpractices include bunkers being adulterated or being off-specification, bunker suppliers under-delivering the quantity ordered or at times short-changing on quantity ordered in collusion with the crew.

These practices are fairly widespread across the industry, and Shipping Companies have over the years adopted various mechanisms to counter them. These mitigatory steps include testing the bunker for quality (to ensure that it is in accordance with the quality specified and that there has been no adulteration), supervising the bunker delivery and transfer process (while being cognisant of things like the Cappuccino effect), and finally ensuring that the company has in place robust and effective policies and codes of conduct governing employees, holistic mechanisms to monitor consumption and conduct bunker supply surveys.

You might also like to read: 

• LNG Bunkering Procedure Of Ships Explained
• 15 Practical Tips For Bunkering and Storage of Fuel Oil On Ships
• Bunkering is Dangerous: Procedure for Bunkering Operation on a Ship
• 13 Malpractices In Bunkering Operations Seafarers Should Be Aware Of
• The Ultimate Guide to Fuel Oil Bunkering Process on Ships

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

How To Reduce Bunker Spend Of Your Ships – 9 Important Points appeared first on Marine Insight - The Maritime Industry Guide

A remotely operated underwater vehicle also called an ROV, is unmanned and usually tethered to the operator. It is an underwater robot that collects data about the underwater world about subsea structures or geological formations like hydrothermal vents. It uses a Remote pilot and automated control technology, making it safe and convenient to operate.

Observation-class ROVs are used for ocean exploration and provide hd images and high-definition video for research and study purposes. The uncrewed vehicle is fitted with additional equipment like water samplers, manipulator arms, etc. Modern ROVs have 8-hour battery life.

An optical cable establishes a connection between the operator and the remotely operated vehicle, which enables its movement.

ROVs are incredibly complex and serve various purposes, from exploration and unmanned expeditions to research and sporting events. They are used by scientists, zoologists, botanists etc. Many industries, like aquaculture, agriculture, etc., use these devices for regular infrastructure inspections and repairs.

In this article, we will look at some of the salient features of ROVs, their usage, categorisation, preparation, launching, operation, and shortcomings.

What is a Remotely Operated Vehicle?

An ROV is essentially a robot that can operate underwater. It works like a miniature submarine, but without the people using it from onboard.

It works wirelessly or through a wired connection, although the latter is more common. Several subsystems together make up the incredibly complex ROV.

The various components that form the broad operating mechanism of the ROV are-

1. Electrical systems (wiring and circuitry),
2. Mechanical structures,
3. Sensors and appendages, and
4. Task-specific structures.

The base frame on which all these systems are supported is the skeleton of the ROV. It is made as light as possible to prevent additional weight and drag during motion.

It is covered with a Manifold structure to prevent accidental damage to the internal components. There are holder clips along its frame members to support wiring and other electrical circuit components.

The skeleton is built to withstand impacts termed as “severe” and uses the triangulation principle of rigid mechanics. To understand how triangulation works, consider a square frame.

Any force at a vertex would lead to buckling and collapse of the frame. Instead, a diagonal member is introduced, providing additional tension strength.

By just adding a single member, the strength is increased across the frame. An X-joint is included in fragile areas, with two diagonal members for added strength in tension and compression.

Subsystems and Materials Used in ROV Design

The electrical systems refer to the wiring and circuitry that make up the heart of the ROV. The only reason they are so helpful and can be used in various fields is the highly robust and complex nature of the electronics outfitted on them.

The primary components include the main motherboard and processing unit, where instructions are fed from a controller and then converted into a physical output.

The controller is manually operated in most cases, and autonomous underwater vehicles (or AUVs) are scarce in this field owing to the various challenges presented.

Signals from the controller input are either wired or wireless based on the level of innovation and design. It may also be task-specific. For instance, a wired robot may get entangled in an underwater wreck site.

On the other hand, a wireless signal may be blocked as the robot heads deeper into the wreckage. So, a careful evaluation of the working conditions and possible hazards should also be done.

Once the signal reaches the onboard receiver, it is conveyed to the mechanical systems. The main system is propulsion, in the form of miniature and specialised marine propellers.

They are powered by small servo motors housed in waterproof casings, the propellers number 2 between 3 to 5 blades per shaft. They can be operated in both clockwise and counter-clockwise directions to create steering.

Some advanced ROVs in wreckage analysis and deep-sea exploration also have swivel jointed propellers. These are rarely used and are more costly than their fixed counterparts. It is only required in situations where very high precision is required.

Sensors and appendages form the very core of the ROVs functionality. The most common equipment includes cameras, depth gauges, temperature, and internal system sensors.

The operator uses cameras since they must have eyes on their surroundings. Depth gauges ensure that the ROV is at the required depth and does not descend into a high-pressure zone.

Temperature zones detect how the water temperature changes and help see subsea thermal vents and thermoclines. Lastly, internal system sensors ensure that the ROV functions perfectly and that all systems work as required.

Task-specific modifications make an ROV customisable and usable in various fields. For instance, historical exploration and wreckage visits can be used to collect artefacts with mechanical arms and tools.

For Subsea geological exploration, the ROV can be fitted with rock cutting tools to extract samples for analysis. For mapping the seabed, it is equipped with LiDAR, SONAR, or RADAR to ping and receive reflected waves off surface elevations and valleys.

Although a primary camera is usually there, they may be specialised cameras capable of thermal imagery, high precision photography, macroscopic lenses etc.

The choice of materials is critical to an ROV. The frame must be light enough not to affect the vehicle’s performance and strong enough to withstand mild to severe impacts.

Electrical systems must be encased in insulated coatings and housed in waterproof containers. Special attention must be paid to anti-corrosion materials to prevent any usage issues.

As the ROV spends a great deal of time underwater, there is a lower chance of rusting (lack of oxygen, which is necessary for rusting).

However, when on the surface, the probability of corrosion increases (dampness combined with atmospheric oxygen). For this, thorough drying must be undertaken, and the ROV must be stored in a dry and clean environment to prevent any fungal growth or corrosion.

The problem of marine growth is prevented by adding special paints that break down existing microbes and prevent new ones from attaching to the ROV surface when underwater.

Usage of ROV

ROVs are used for various purposes and are outfitted accordingly. This is why most unmanned vehicle manufacturers provide a basic skeleton or structure on which modifications can be made. The basic structure is known as the “frame” or “template” of the ROV. This section looks at the various uses to which these devices are put.

An underwater ROV is well-equipped with modern technology. It consists of a lighting system and a video camera to record a better subaquatic panorama and contribute to geology education and learning about sea life.

With continued developments in the arena of technology, the latest technical concepts are being imparted to remotely operated vehicles to amplify their original capacities to a greater extent. Extra machinery can comprise a static camera, a water sampler or even a manipulator.

Moreover, a remotely operated underwater vehicle can incorporate advanced instruments for appropriate measurement and evaluation of current temperature, light penetration and water clarity.

These are commonly used in scientific and exploratory ROVs to learn about the underwater environment. Chemical analysers also study water’s specific makeup or composition at various locations and depths.

ROVs or underwater robots were primarily invented to serve an industrial purpose regarding regular pipeline inspection (both interior and exterior) and to conduct structural testing methods on specific platforms from various offshore locations.

These ROVs are even helpful for exploring oceanic water wreckage sites and historical ruins. The ROVs cater to the needs of numerous science expeditions and several educational programs at aquaria.

Categorisation of ROVs

Underwater ROVs can be distinguished into various classes by evaluating their weight, power, abilities and sizes. The Micro ROV is small-sized and weighs below 3kg.

The primary classifications used are as follows:

1. Micro ROVs
2. Mini ROVs
3. General ROVs
4. Inspection Class
5. Light Work Class
6. Heavy Work Class
7. Trenching and Burial ROVs

These attributes enable the ROV to explore tiny cavities or pipeline cracks, which is physically impossible for a diver to achieve.

The Micro ROV is small-sized and weighs below 3 kg. These attributes enable the ROVs to explore minuscule cavities or pipeline cracks, which is physically impossible for a diver to achieve

On the other hand, the typical Mini underwater ROVs have a standard weight of around 15kg. It takes just one person to efficiently operate it from a boat and carry out an underwater expedition.

The micro and mini categories of remotely operated vehicles can be termed an alternative “eyeball” as they do not participate in intervention undertakings.

The General ROV type is usually below 5 HP (propulsion) and comprises three-finger manipulators, like in the old RCV 225. These are specially built to aid in light survey tasks, as these usually bear a sonar unit.

The standard underwater depth is around 1000 meters, but one ROV has been upgraded to even traverse to 7000 meters.

The Lightwork class remotely operated vehicle is generally below 50 HP and can support several manipulators. These ROVs allow a maximum working depth of 2000 meters. Polyethene, a kind of polymer, is used in construction which varies from the typical aluminium alloys or stainless steel.

The Heavy workplace machine supports below 220 HP with two manipulators and can achieve a depth of 3500 meters.

These ROVs can have a lifting payload of over 5,000 kilograms. They can also be modified to work with multiple manipulators. The most common application of the heavy work class is in deep-water installations and subsea tie-ins.

The Trenching ROV offers a 200-500 HP range and can be utilised to 6000 meters. While most propulsion systems on these ROVs function below 500 HP, there are underwater vehicles that may function at powers of nearly 600 HP or more.

They are commonly used in cable laying, the safe creation of seabed trenches, and the partial or complete anchoring (burial) of subsea components used in the oil and gas industry.

Lastly, there is another classification of submersible ROVs based on how they are launched. There is a system known as Tether Management System (or TMS) that controls the payout for the umbilical cord that delivers power and control to the ROV. It is known as a free-swimming vehicle when it is directly connected to the ship or observation platform.

In such cases, it is neutrally buoyant. On the other hand, some ROVs are stored within compartments called garages that are lowered into the ocean.

During the launching, the ROV ejects from the submerged compartment and has its rope connected to the garage, NOT the ship. The choice of the launching system depends on usage, depth, function, and geographical factors.

Preparation and Launching of ROVs

The size range of a remotely operated vehicle is imposing, as it may vary from a small bread box to a minor truck. Preparing an underwater vehicle launch can be straightforward as the robot can be merely dropped into the water from the vessel.

The recovery procedure may involve big windlasses to uplift the robot from the water. Generally, A-frames are available to swing over the ROV safely onto the deck.

Different structures called “garages” are sometimes present, which are lowered to the rear end. These “garages” can act like a temporary yet secure den, and the ROVs can return once the expedition gets over.

The occasional excursions carried out by remotely operated vehicles are considered much safer compared to the usual diving expeditions, which can lead to physical injury or even death.

A remotely operated underwater machine can prove to be highly efficient when dealing with a submersible, as the cutter blades or the manipulator’s arm can come in handy while rescuing the submersible if it is stuck and unable to move freely.

Another drawback of submersible ventures is that bad weather conditions can be a significant hindrance, whereas a remotely operated vehicle can remain unaffected. As an added utilisation, research can initially submerge the ROV into the water to explore the detailing of the particular underwater site and then decide if it is safe enough to send a submersible.

Before ejecting the ROV from the side of the ship or launching the platform, the ROV is gently lowered into the water. It is not allowed to splash because of the risk of damage to the sensitive equipment on board. Windlasses may be used here, or if the freeboard isn’t too high, it may be manually lowered by hand.

A moon pool may be used in choppy waters that increase the risk of damage during splash zone entry. Moon pools are enclosures within a hollow vessel with the water surface at its lower end.

A column of water is created in which the water is relatively steady. Dampers are also used to reduce the heaving motion to prevent resonance-related damage. ROVs can be lowered through the moon pool in poor weather conditions.

Famous ROVs

Amongst well-known underwater ROVs, the Ventana runs on hydraulic power and can traverse to a depth of 1850 meters. The Ventana is manipulated from the RN Point Lobos ship deck.

On the other hand, the MBARI franchise purchased the ROV Doc Ricketts way back in 2008, which offers an incredible capacity of going deep down to a depth of 4000 meters.

This remotely operated vehicle has undergone constant up-gradation ever since. The Doc Ricketts served as a magnificent replacement to the earlier ROV Tiburon, which could also travel down 2.5 miles.

These unique submarines have enabled easier exploration of several deep-sea gas and oil reserves. Many oil reserves were hard to locate by using the divers and hence caused a major commercial setback.

Interestingly, the undetermined locations of famous shipwrecks like the RMS Titanic, USS Yorktown, SS Central America, and the German warship Bismarck have been discovered due to some help from the ROV industry.

In the case of SS Central America, the remotely operated underwater vehicle has also been able to retrace and gather essential materials from the seafloor of the shipwreck.

Shortcomings

The preferred design is a high-power signal that can control ROVs across a considerable distance. It will have a more extended range than currently possible with tethered structures. However, high power and frequency may affect marine life.

The other alternative is a low-power primary signal coupled with several amplifiers at regular intervals to create a more extensive range for the ROV.

Although it will be more expensive, it is preferred from an ecological viewpoint. Unfortunately, the issue with the low power option is that it would cause cluttering of the sea surface due to a larger number of amplifiers required to function.

A massive setback of a remotely operated underwater vehicle is that it lacks human presence, making it challenging to execute visual surveying down underwater. The car remains attached to the main boat above water through intricate wiring, leading to a restriction of free movement.

Research and innovation are currently being undertaken in the field of wireless control for ROVs. The proposed design suggests two main models for implementing this control.

The preferred design is a high-power signal that can control ROVs across a considerable distance. It will have a more extended range than currently possible with tethered designs. However, high power and frequency may affect marine life.

The other alternative is a low-power primary signal coupled with several amplifiers at regular intervals to create a larger range for the ROV. Although it will be more expensive, it is preferred from an ecological viewpoint.

Unfortunately, the issue with the low power option is that it would cause cluttering of the sea surface due to a larger number of amplifiers required to function.

Frequently Asked Questions

1. What is an ROV?

A remotely operated underwater vehicle also called an ROV, is unmanned and usually tethered to the operator. It is an underwater robot that collects data about the underwater world about subsea structures or geological formations like hydrothermal vents.

2. What is the purpose of ROVs?

Observation-class ROVs are used for ocean exploration and provide hd images and high-definition video for research and study purposes. ROVs are incredibly complex and serve various purposes, from prospecting and unmanned expeditions to research and sporting events. They are used by scientists, zoologists, botanists etc. Many industries, like aquaculture, agriculture, etc., use these devices for regular infrastructure inspections and repairs.

3. How are they operated?

It uses a Remote pilot and automated control technology, making it safe and convenient to operate. The uncrewed vehicle is fitted with additional equipment like water samplers, manipulator arms, etc. Modern ROVs have 8-hour battery life.

4. What are some of the famous ROVs?

The Ventana runs on hydraulic power and can traverse to a depth of 1850 meters. The Ventana is manipulated from the RN Point Lobos ship deck. MBARI franchise purchased the ROV Doc Ricketts way back in 2008, which offers an incredible capacity to go down to a depth of 4000 meters.

5. What are some of the achievements made possible due to ROVs?

They have enabled easier exploration of several deep-sea gas and oil reserves. Many oil reserves were hard to locate by divers. Also, undetermined locations of famous shipwrecks like the RMS Titanic, USS Yorktown, SS Central America, and the German warship Bismarck have been discovered due to the help of the ROV industry.

You might also like to read

• A Career in Marine Remotely Operated Vehicles (ROV) Industry [Q&A]
• How Subsea Components Of ROV Sustain Tremendous Seawater Pressure?
• Watch: MOL Conducts Underwater Drone Demonstration Test For Vessel Bottom Inspection
• Watch: Subsea Support Vessel MV Deep Helder Launched At Foxhol Yard
• 11 Technologies That Are Used To Study And Understand Oceans
• Watch: Launch of Ulstein designed PSV’ Energy Duchess.’

Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

What is Remotely Operated Underwater Vehicle (ROV)? appeared first on Marine Insight - The Maritime Industry Guide

SSB radio is used by boats or yachts for communication at sea. It is part of the Global Maritime Distress, and Safety System established under SOLAS, the international convention for the safety of life at sea.

The full form of SSB Marine radio is Single Side Band radio. The SSB radios offer quick access to over 700 radio channels. MF or medium frequency SSB radios range about 400 nautical miles, while HF or high-frequency SSB radios range a thousand miles.

Hence, they have a larger reach than VHF radios, ranging from 35 to 50 nautical miles. The system consists of chargeable lithium-ion batteries, chargers, an external antenna, and an automatic antenna tuner and is used by sailors, mariners and naval forces.

The State of California declared that these batteries contain certain cancer-causing chemicals and should be handled cautiously. While charging the radio system, one should place it on a fire-proof surface and not leave it unattended for a long time. Also, good quality cable connections should be installed for greater transmission clarity.

While many believe that a satellite phone may come in handy during emergencies, an SSB radio with marine SSB transceivers is the most helpful tool since it sends distress signals to all ships in the vicinity and alerts the rescue authorities automatically. In contrast, you can call just one number through a satellite phone. Also, pairing the SSB radio with a Pactor modem would allow one to receive weather faxes, weather GRIB Data and e-mails onboard a vessel.

Depending on the requirement, one can opt for SSB amateur radio systems cheaper than SSB Marine radios. However, an amateur radio certificate is more difficult to get than a marine radio license or a Long Range Certificate. Also, the expensive SSB marine radios have a DSC or Digital Selective Calling function too.

The SSB radio was first used as a part of the navigational radio system after World War II. The main reason for introducing the SSB radio system was the problems caused by the AM (Amplitude Modulation) radio system.

One of the main disadvantages or problems of the AM radio system was that it absorbed a considerable amount of unwanted power and space. Also, the AM system was not foolproof. The messages and information passed through the AM system could be listened to and monitored by unwanted channels leading to important information being passed on and emergencies being created.

The SSB radios offer a wide variety of services like a two-way communication marine radio system with the captains of other boats, yachts and the coast guards. Apart from this, the SSB radios are not affected by distance. They can be easily used for calls and messages between yachts or boats far away from each other without disrupting or distorting transmission. In addition to being a marine radio system that offers full-proof communication channels, the SSB radio system also provides entertainment in the form of music to the boat’s crew. The SSB radio thus provides a comprehensive marine radio communication system to the shipping industry.

However, a specific transmitter must be equipped in the boat to receive and send messages through an SSB radio system. If this transmitter is not fixed to the ship, then routine radio communication transmitters like the AM radio channel would be used for receiving the SSB radio signals. The voice modulation in AM radio frequency channels will be vastly different because of the difference in the transmitting channels. This could make the messages distorted, leading to further confusion and chaos.

The appropriate systems that need to be used to read the messages sent via the SSB radio system correctly are the Beat Frequency Oscillator (BFO) or the Carrier Insertion Oscillator (CIO). The system of SSB radios is a significant development in the field of radio communication. This development will only increase in the days to come, helping the seamen navigate and communicate even more effectively than ever before.

Frequently Asked Questions

1. Is SSB the same as HAM Radios?

HAMS make use of the same kind of SSB but on HAM Frequencies. The coast guard uses frequencies on marine channels. However, in case of an emergency, they can also call out to all ham radio operators on ham frequencies.

2. How far can you talk on an SSB Radio?

An SSB Distress call is sent to all ships within range, and the range can be thousands of miles. It is also sent to the nearest search and rescue services, depending on your location. On the other hand, a satellite call can be dialled to only one number.

3. What is an SSB Radio system?

SSB Marine Radio or Single Side Band Radio is used for communicating over very large distances without the requirement of any subscriptions or ongoing costs and tariffs. It is mainly like AM and FM.

4. What is the importance of SSB Radio onboard ships?

Apart from being a system that provides foolproof communication channels, ensuring the safety of vessels at sea, the SSB system also keeps the sailors entertained as one can tune in to various channels and hear music or even weather reports. Hence, it offers all-around communication services to the shipping sector.

5. Do you need a licence to use SSB Radio?

Yes, all two-way communication radios require a licence which depends on the type of radio one has. One can opt for SSB amateur radio systems which are cheaper than SSB Marine radios. However, an amateur radio certificate is more difficult to get than a marine radio license or a Long Range Certificate.

You might also like to read-

• A Brief Introduction to Survival Radios
• Obsolete-yet-Famous Marine Jobs: Radio Officers
• What Are Marine VHF Radios, Marine GPS and Marine Autopilots?
• Introduction to Global Maritime Distress Safety System (GMDSS) – What You Must Know
• What is Maritime Mobile Service Identity?

Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

What are SSB Radios? appeared first on Marine Insight - The Maritime Industry Guide

The role of fire-fighting systems on ships cannot be more emphasized. Time and again, deadly fires have ravaged merchant ships at sea, away from the land without any hope of shore-based assistance and have caused large-scale destruction to the ship, cargo and, even worse, resulted in the loss of human lives.

Now imagine such a scenario on a passenger ship with thousands of lives on board; the mere thought is terrifying as the loss of lives could be potentially much more. For this reason, it is critical for the cruise ships to be fitted with means of fighting fires, both in the passenger areas and crew areas, including technical spaces.

As in the case of cargo ships, even here, the most likely place for a fire to potentially start is the engine room. The heat from running machinery and exhaust, oily surfaces and abundant air supplied through blowers make it a very hazardous and vulnerable space for fires to start. If not curbed or controlled initially, a fire can spread rapidly to other areas around the ship, causing large-scale devastation and creating havoc.

It is for this very reason that cruise ships are fitted with multiple systems for fire-fighting. For example, many cruise ships are equipped with a water-mist system, in addition to the carbon-dioxide fixed fire-fighting system (for technical spaces) and sprinkler system (for crew and passenger areas). However, many latest passenger ships use only the water-mist system for all areas (crew, technical and passenger spaces).

For machinery space fires on these ships, the water-mist often serves as the primary means of fire-fighting. In contrast, the CO2 is only used as a backup in cases where the fire has become large and uncontrollable, leaving no option but to release it.

In the water-mist system, water in the form of a very fine mist is discharged from the nozzles or sprinklers installed on top of the protected equipment or area.

The advantages of using water in this form for fire-fighting as compared to the traditional sprinkler system are: –

• Increased area of coverage and better distribution of the fine water-mist
• Better penetration to the seat of the fire
• Rapid cooling of the seat of the fire and surrounding areas
• Rapid evaporation of the micro-fine droplets to steam helps in smothering the fire (oxygen-starvation).
• Little to no risk of any damage to equipment as water is in the form of a fine mist.
• Lesser consumption of water because of reduced droplet size as compared to the sprinkler.

Its relative advantages over the traditional carbon-dioxide fixed fire-fighting system are: –

• Can be released much more quickly than CO2, which requires perfect sealing and evacuation of personnel.
• This saves precious time and minimizes further spreading of fire.
• No risk of the presence of gas pockets after the fire is extinguished, unlike CO2.
• No risk to life in case of release (accidental or otherwise)
• Unlike the CO2 system, which requires bulk release, the water-mist is released to protect only the area necessary/equipment affected by the fire.
• The refilling process is much easier and costs much less compared to CO2 system.
• No specialized shore-based assistance is required for maintenance, unlike CO2 system, which requires refilling and pressure-testing of the bottles every few years.

The Hi-Fog water-mist system

This is a type of water-mist fire-fighting system which is developed by Marioff Corporation and which are seen installed on a few passenger vessels.

It basically consists of two individual units. A Master unit at the forward of the ship and a Slave unit at the aft. Each unit has the arrangement as per the below figure.

Operation of the Hi-Fog water-mist system

The freshwater required for the system is stored in a tank. This tank has a level gauge and high/low-level float switches. The water in this tank is replenished according to its level.

When the level of water goes down, it activates the low-level float. This sends a signal to the automation to start the Hi-fog supply pump (not shown in the above figure) and also to open an automatic valve in the filling line of the pump.

This pump supplies/replenishes fresh water to the tank from one of the ship’s technical water tanks via a filter and automatically stops when the desired level is reached. This also closes the automatic valve.

The supply pump operation (cut-in/cut-off) can be tested as a monthly routine by draining the tank manually through a drain valve provided at the bottom of the tank. This drain line is connected to the bilges.

In the normal condition, a pressure of 18-24 bar is always maintained in the Hi-fog system. This is ensured by an air-operated low-pressure diaphragm pump whose purpose is to compensate for small leaks and losses.

In case the pressure drops below 18 bar (in case of fire when Hi-fog releases or a major leak), the high-pressure pumps automatically start. These are positive displacement pumps that can raise the system pressure to around 140-150 bar when operated. There are usually 8-10 pumps but I have only shown 3 pumps in the above figure, for ease of understanding.

Each high-pressure pump is provided with a relief valve on the discharge side. This is to avoid damage to the pump and the line in case of operation of the pump with the main isolating valve closed, such as during the testing of the pumps. The relief valve operates to release the excess pressure back to the tank or suction side of the pump.

The high-pressure pumps are always in automatic mode. The pumps once started automatically, have to be stopped manually once the fire is extinguished. Thereafter, an automatic drain valve (not shown in the figure) drains the Hi-fog line to bring the pressure down from around 150 bar to the normal value of 18-24 bar.

The high-fog common main isolating valve on the discharge side of the pumps is always kept open. During routine monthly testing of the high-pressure pumps, the main isolating valve is manually closed and the pumps are switched to manual mode.

The pumps thus started, are tested for the build-up of pressure, any abnormal noise/vibration and operation of the relief valve. The oil level inside the pumps should also be checked during machinery rounds and replenished as required. Oil replacement should be done as per PMS.

Master, Slave Operation and Water Cylinders

In case of a major conflagration anywhere on the ship, the forward unit which is set as Master, operates first. If the fire does not come under control, the Master unit (forward) sends a signal for the Slave unit (aft) to operate.

If in case, the fire still does not come under control, some ships are provided with water cylinders (usually 10 numbers each containing 50 litres of water) as additional freshwater supply.

Nitrogen pilot cylinders are provided which act as an actuation mechanism for opening/releasing the water cylinders. In a case of a situation where despite both the Master and Slave unit together being unable to extinguish the fire, the nitrogen is released with the help of electrical signals, which in turn, actuates and releases/opens the water cylinders. Pressurized water then goes to the Hi-fog heads.

In addition to all the above, a seawater supply line (usually from the fire line) is also provided to the Hi-fog system. This is in the case where the freshwater in both the Hi-fog tanks (forward and aft), in the technical water tanks and in the water cylinders might not suffice. Two valves are provided for seawater supply, which is in a normally closed (NC) position.

If seawater has been used, once the fire is extinguished, the lines have to be thoroughly flushed with fresh water to minimize the possibilities of corrosion and scaling due to seawater, before filling with fresh water and putting the system on standby for use.

Section valves and nozzles

The Hi-fog system has many section valves for supply to machinery spaces and accommodation. Each section valve caters to a particular location, for example, there is one section valve for each diesel generator, each boiler, each purifier room (forward and aft), each incinerator and for accommodation areas, a section valve for each deck.

There is a difference between the section valves, lines and the design of the Hi-fog nozzles provided in the machinery spaces and the ones provided in the accommodation areas.

The section valves in the machinery spaces are normally closed (NC) and can be opened either manually or by means of push-button from the engine control room.

This means that the Hi-fog lines in the machinery spaces are dry in the normal condition and only when there is a fire, the valve is opened by the watchkeepers and water supplied to the Hi-fog nozzles.

Testing of machinery space section valves

Testing of the section valves is carried out as per PMS. The Blocking valve (shown in the above sketch) supplying the water to the Hi-fog nozzles is shut and the test valve (also shown) is opened. Then the section valve is opened (either locally or remote) and water flow is checked.

The accommodation section valves are normally open (NC) which means that the lines are always wet, i.e., the water is always available up to the nozzle or sprinkler head. The nozzles themselves are of the bulb-type, a bulb filled with a heat-sensitive fluid that expands and breaks in case of temperature increase due to a fire, thus releasing the water.

Hi-fog distribution in accommodation areas of a passenger ship

The reasons for this difference are:

• The accommodation areas including passenger cabins are not always occupied. Therefore, in case of a fire, the system should be designed in such a way so as to operate quickly & automatically to minimize damage, unlike machinery spaces and engine control rooms which are always manned.
• The machinery spaces are at a much higher temperature than the accommodation areas. So, if wet lines and heat-sensitive bulb-type nozzles are used, there might be an accidental release of Hi-fog due to breaking of the nozzles under higher temperatures especially in hot engine-room areas such as near the DGs and purifier rooms, even without any actual fire.

Therefore, the machinery spaces have dry lines and the accommodation has wet lines.

However, in both cases, the solenoid-operated section valves have to be closed manually by push-buttons from the engine control room, once the fire is extinguished. For the accommodation, these valves are opened after the replacement of the broken nozzles and are always kept open thereafter (NO position). In the engine room, they are of the NC type.

For the machinery space section valves, in addition to operation from the engine control room, the local push-button release is also possible. This is provided for redundancy purposes and in order to save time in case of a fire or a potential threat of fire.

The Hi-fog system as explained above is found in many modern and newer ships and provides the versatility of the ability to fight fires both in the accommodation areas as well as engine rooms. The system is widely accepted because of its efficiency, redundancy, little to no risk of exposure or evacuation and ease of operation.

Due to the above advantages, the system has found its use as a retrofit in many older passenger ships as well. However, due to higher retrofitting costs and the complication of remodelling and restructuring, the use of Hi-fog in older ships is generally restricted to high-risk areas in the machinery spaces such as boiler, DG, purifier & incinerator rooms

For accommodation areas, a more traditional sprinkler system is used.

Sprinkler system

Sprinkler system for accommodation fire-fighting in older passenger vessels

The sprinkler system shown is used for fire-fighting in accommodation areas on older passenger ships. This system is designed for use with freshwater normally supplied from one of the technical water tanks as well as from seawater in case of emergency. The system components are: –

Surge Tank: This is a pressurized vessel that is used to maintain the system pressure at about 10-12 bar. It has an air supply and a level gauge.

Additional freshwater tank: This as the name suggests is a supplementary source of freshwater and is only used when the main freshwater tank is empty or not available. This tank is filled with technical water from the ship’s TW system.

Booster pump: This pump supplies technical water from the designated tank to supply water to the topping-up pump.

Topping-up pump: This pump runs in series with the Booster pump in normal situations but can also run independently to top-up the system (surge tank) directly from the additional freshwater tank when the designated TW tank or booster pump, are not available.

Sprinkler SW pump: In case of emergency, the system can also be operated on seawater through the sprinkler SW pump. Also, the pump cuts in automatically whenever the system pressure drops below 5 bar through the pressure switch.

Non-return valves: There are two NRV’s provided. One is in the SW pump discharge line in order to prevent backflow & thereby loss of system pressure via the SW supply line. Another one prevents backflow to the surge tank.

Pressure Gauge: It indicates the system pressure.

Line valves: These are usually butterfly valves with limit switches for remote indication for an OPEN or CLOSE position. There are five valves namely V1, V2, V3, V4 & V5.

Normal set-up

During the normal set-up of the system, the FW level in the surge tank is maintained at about 3/4th as can be observed from the level gauge. A column of air must be maintained inside the surge tank. This must be checked by the watchkeepers during their routine rounds as it will help in maintaining the system pressure and also prevent the surge tank from becoming too full with water.

The booster pump and topping-up pump are kept in automatic mode and the valves are lined up such that the system can supply water to the various sprinkler stations in the accommodation area from where water is further supplied to sprinkler heads in various cabins or guest spaces. The set-up is as below: –

• VALVE V1 IS IN OPEN CONDITION
• VALVE V2 IS IN OPEN CONDITIONVALVE
• V3 IS IN OPEN CONDITION
• VALVE V4 IS IN OPEN CONDITION
• VALVE V5 IS IN CLOSED CONDITION

In case of a fire, the booster and topping-up pumps automatically start as the water level in the surge tank goes down. If the fire is not extinguished, the pumps will keep running until the low level of the designated technical water tank. Beyond this, the additional freshwater tank can be put to use via the top-up pump, by opening a valve.

When the additional freshwater tank empties, the system pressure drops and the sprinkler seawater pump starts automatically through the signal from the pressure switch, to supply seawater for fire-fighting.

If seawater is used, the system needs to be flushed with freshwater before reuse.

System Testing

The system must be tested as per PMS and reported. This is important so as to ascertain the proper working of all the pumps, valves and pressure switches. The top-up pump and booster pump must be put to manual or off-position before in order to test the sprinkler seawater pump operation. The system is set up as below: –

• VALVE V1 IS IN CLOSED POSITION
• VALVE V2 IS IN CLOSED POSITION
• VALVE V3 IS IN CLOSED POSITION
• VALVE V4 IS IN OPEN POSITION
• VALVE V5 IS IN OPEN POSITION

Since valve V4 is already in the open position, when valve V5 is opened as per the sequence mentioned above, the water in the pipeline between the closed valves V2 and V3 starts draining to the bilges. This drop in pressure can be observed through the pressure gauge. When the pressure drops below 5 bar, the pressure switch causes the seawater pump to cut in.

At this point, the pump must be manually stopped and V5 closed immediately. All other valves should be put back to their normal positions and all pumps should be put back to automatic.

Water quality testing

It is important to test the water quality for both the water-mist as well as the sprinkler system from time to time. For the water-mist, the samples are taken from the test/draining valves and for the sprinkler system, they are taken from various sprinkler stations. It is tested for pH, conductivity and chlorides.

If chloride content is found high, the system needs to be drained, flushed and refilled with technical water to prevent/minimize corrosion and decay of pipelines and fittings.

Summary

Both water-mist and sprinkler systems are critical keeping in mind the safety of the ship, crew, passengers and readiness in tackling fire emergencies onboard.

The water-mist system, in fact, has super ceded the sprinkler system in many modern passenger vessels due to its higher efficiency, less water consumption, quick detection of fire and release, lower operational costs, little to no risk of damage to area/equipment, technological advancement, versatility and adaptability (the same system can cover all areas of the ship).

It has even super ceded the traditional fixed fire-fighting CO2 systems in terms of quick releasing capabilities and no obvious threat to life on release. It is much more economical and easier to replenish the system after use and to carry out routine maintenance. Also, it gives more flexibility of operation.

Due to these reasons, the water-mist has now become the preferred or primary source of fire-fighting on cruise vessels, machinery spaces included. The CO2 system still exists though, but only as a backup and the last resort in case of an uncontrollable machinery space fire.

Many older passenger vessels too, have retrofitted water-mist systems on board in addition to existing sprinkler systems. But it looks like sprinkler systems are being phased out with increasing acceptance for water-mist and technological advancements.

You might also like to read:

• How Ships are Protected from Lightning; Ships Earthing System
• How Are Cruise Ships Powered?
• Engineering Department Onboard Cruise Ships; A Detailed Guide
• How Do Cruise Ships Get Fresh Water?
• Titanic vs Modern Cruise Ship: How Ships Have Evolved 

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader

Water-Mist And Sprinkler Systems On Passenger Ships appeared first on Marine Insight - The Maritime Industry Guide

The operation of the main engine, various types of auxiliary machinery, and handling of fuel oil results into the production of sludge on board ships. This sludge is stored in various engine room tanks and is discharged to shore facility or incinerated onboard. Also, various leakages from seawater and freshwater pumps, leakages from coolers, etc. generates bilges.

In this article, we will see from where sludge and bilge are generated, how they are stored in engine room tanks, what record keeping is done, and how sludge and bilges are incinerated, evaporated, or discharged.

Sludge Production On Ship

Sludge on board ship comes from various sources like:

1. Fuel Oil Purifiers

The fuel oil purifiers have a designated discharge interval depending on the quality of fuel oil. After every set interval the bowl of the purifier discharges sludge accumulated, into the sludge tank or designated fuel oil purifier sludge tank. This sludge contains oily water and impurities which has been separated from the fuel oil by the purifiers.

2. Lube Oil Purifiers

The lube oil purifiers have a designated discharge interval depending on the quality of lube oil and the running hours of Main engine and Auxiliary generators. After every set interval the bowl of the purifier discharges sludge accumulated, into the sludge tank or designated lube oil purifier sludge tank. This sludge contains oily water and impurities which has been separated from the lube oil by the purifiers.

Related Read: 8 Ways To Optimize Lubricating Oil Usage On Ship

3. Main Engine Scavenge Drains

When the main engine is running, oil residue in scavenge spaces is collected from the cylinder lubrication being scrapped down from the liners. This oil is drained through scavenge drains of each unit of the main engine and collected into the sludge tank or designated scavenge drain tank.

Related Read: Everything You Ever Wanted to Know About Scavenge Fires

4. Main engine stuffing box

When the main engine is running, oil residue is collected from the stuffing box scraping oil on the piston rod. This oil comes from the stuffing box drains of each unit of the main engine is collected into the sludge tank or designated Stuffing Box drain tank.

5. Save all tray drains of oil machinery

All fuel oil machinery i.e. pumps, filters, purifiers, etc. have the tray under them to collect any leakage if occurs. The drain of the tray goes into sludge tanks.

6. Miscellaneous

They are other drains going into the sludge tank, for example, air bottle drains, fuel oil settling and service tank drains, etc. All these drains are oily water and are collected in sludge tanks.

Related Read:  A Comprehensive List of Fuel, Diesel and Lube Oil Tanks on a Ship

Sludge Tanks 

The number of sludge tanks varies from ship to ship, it depends on from which shipyard ship is built and also depends on the machinery in the engine room. Some ships have one common sludge tank and some have individual sludge tanks. Sludge pump is used to make internal transfers and transfer to shore reception facility. All sludge tanks have to be in compliance with flag state oil record book and every transfer has to be recorded in oil record book. All designated sludge tanks and bilge tanks have to be mentioned in International Oil Pollution Prevention (IOPP) certificate. Any transfer from or into IOPP tanks has to be recorded in Oil Record Book for the Engine room by the Chief Engineer.

Sludge Incineration And Oily Water Evaporation 

The sludge generated have some water content in them coming from HFO & LO purifiers, from HFO settling and service tank drains, Air bottle drains. This water can be evaporated in the waste oil tank. Sludge is transferred from various sludge tanks into waste oil tank for incineration. Before incineration, all the water has to be evaporated so that sludge can be burned efficiently in the incinerator.

Related Read: Construction and Working of Waste Oil Incinerator

Sludge is transferred from HFO purifier sludge tank, LO purifier sludge tank and Oily bilge sludge tank into the Waste oil tank and steam valves (inlet and return) are kept open for water evaporation. The tank temperature reaches 100 degrees Celsius and water starts evaporating, when the temperature goes above 100 degrees Celsius it indicates that the water has been evaporated and oil has started to heat up. Now the sludge is ready for incineration. The quantity of water evaporated has to be recorded in the oil record book.

If there is a common sludge tank, then water is allowed to settle for few days in the common sludge tank at the bottom. After the water has been settled at the bottom, suction from the bottom is taken and transferred to waste oil tank for water evaporation.

Before transferring any sludge into the waste oil tank, the temperature of the waste oil tank should be less than 90 degrees Celsius to prevent boil off in the tank. Boil off will result into instant tremendous pressure rise in the tank.

After the water has been evaporated and sludge is heated up, it is ready for incineration. For incineration, follow these steps:

• Drain and check if any water from waste oil (sludge) in the tank before burning.
• Agitate the sludge in waste oil tank if an agitator is present. This will help in emulsifying the oil into an even mixture for fine atomization.
• Warm up the incinerator with diesel oil. Incinerator should be operated by a qualified person with all necessary safety precautions.
• After warming up, open the feed valve for waste oil from the waste oil tank. Ensure steam tracing is proper for the waste oil line and strainers are not chocked. Adjust the damper and temperature according to the manual.
• The waste oil pump will take suction from the waste oil tank. Continue burning waste oil and maintain incinerator parameters. Depending on the capacity of the waste oil pump, compare and check how much waste oil is burning in the incinerator. The final amount of sludge incinerated has to be recorded in an oil record book.

The amount of sludge generated on board is with the proportion of the fuel consumption. In general, average sludge production is considered to be 1.5% of total fuel consumption. If the sludge generation is more than 1.5%, sludge production of the ship is high.

Engine Room Bilge Water Generation

Leakages from fresh water and sea water pumps, coolers are collected in bilge wells in the engine room. Bilge wells are located at the forwarding of the bottom platform at the tank top port and starboard. Other bilge wells are at the aft of engine room, recess bilge well under the flywheel, shaft tunnel bilge well if separate space for shaft tunnel is present.

All the leakages in the engine room bottom platform are collected in these bilge wells and can be transferred to the bilge holding tank via the oily bilge pump. The oily bilge pump may also pump these spaces to the sludge tank (via the sludge pump bypass line) and the deck connections for discharge to shore or barge.

Related Read: Good Bilge Management Practices 

The oily bilge pump transfers bilges to bilge holding tank via bilge primary tank. Bilge primary tank is of smaller capacity present to separate oil from bilges. Bilge primary tank is overflowed to bilge holding tank. Any oil layer formed on top of the bilge primary tank can be removed.

The bilge tanks in the engine room are:

Bilge Holding Tank

Bilges from bilge well are transferred here and stored to be discharged overboard via oily water separator and PPM monitor or to be discharged ashore.

Bilge Primary Tank

Bilge is transferred here to separate oil by gravity. Any oil layer formed on the top can be removed

Bilge Evaporation Tank

Present on some ships in which bilge can be transferred and evaporated by heating.

Air cooler drain tank

All the moisture from Main Engine scavenge air coolers and generator scavenge air cooler is drained in this tank. They might have some oil as engine room air may contain oil vapour. Hence they are discharged overboard via PPM monitor.

Atmospheric air contains moisture and when this air is compressed in the turbocharger and then cooled in the air cooler, the moisture condenses to form water droplets. If these water droplets enter the cylinders with the scavenge air they can remove the oil film from the liner, resulting in excessive cylinder liner and piston ring wear.

Additionally, removal of water droplets from the air minimises the risk of sulphuric acid formation in the cylinders and uptakes due to the dissolving of acid products of combustion in the water droplets. In order to prevent these problems, water is removed from the combustion air by water separators fitted after the scavenge air coolers. The water droplets are directed from the air coolers, via drain traps, to the air cooler drain tank.

Related Read: Understanding Hot And Cold Corrosion In Marine Engines

This tank is pumped overboard by the air cooler drain discharge pump or bilge pump, the discharge from this pump overboard. The water flowing to the overboard discharge line passes through an oil detector, which monitors the oil content of the water being discharged overboard. It is also possible to pump the contents of the air cooler drain tank to the bilge holding tank using the oily bilge pump.

All the bilge transfers, bilge discharge overboard or to shore, bilge evaporation has to be recorded in oil record book. Whenever Oily water separator is operated, the position of the vessel at starting and stopping has to be recorded along with time and volume of bilge discharge. The PPM monitor will not allow discharge of bilge having more than 15ppm of oil content.

Related Read: How to Operate an Oily Water Separator (OWS) on Ship?

Cargo Hold Bildge Water Production

Cargo holds, generally of container vessels, have bilge wells located at the bottom on each side, port, and starboard. The hold bilges are normally pumped overboard through bilge eductor from Fire & GS pump as they contain only water. However, before pumping hold bilge wells, a visual inspection has to be carried out of the bilge wells. If any traces of oil is found, then they have to be pumped to the hold bilge collecting tank or other designated engine room tank, from where they would be processed in the OWS. Before any bilges are pumped directly overboard, it must be ensured that no local or international anti-pollution regulations will be contravened. The eductor should only be used when at sea.

The hold bilge line additionally takes suction from bow thruster room bilge wells, pipe duct bilge wells, chain locker bilge well, and forepeak void space. All the bilge wells valves can be operated remotely from the ship’s office or engine control room.

Sludge and bilge management on-board are very critical and important. MARPOL rules are very stringent and have to be followed properly to prevent pollution at sea. Any violation of MARPOL can lead to imprisonment and huge fines.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

An Overview Of Sludge And Bilge Management Onboard Ships appeared first on Marine Insight - The Maritime Industry Guide

The generator onboard, being the powerhouse of the ship, requires regular maintenance and overhauling to ensure efficient and safe operations. A responsible marine engineer will never wait to carry out maintenance procedures until its machinery is on the edge of a breakdown. Instead, he/she will take all necessary precautions to prevent his ship from any impending troubles, which can take place because of engine room machinery failure or breakdown.

There is a thin line between the starting of a problem and the problem taking the shape of a major issue.  It is only a ship’s engineer who can assess this situation.

Still, cases are observed every year wherein the auxiliary engine breakdown occurs even after giving several indications, foreboding the unfortunate.

Listed below are ten cases wherein you must immediately start the standby engine and stop the auxiliary engine in “trouble” before a dangerous situation takes shape of a major disaster:

1. Abnormal/ Queer Sound: The ship’s generator engine comprises of heavy oscillating and moving parts. The attached auxiliaries such as turbochargers, pumps etc. are also high-speed machines which produce a good amount of sound. Any abnormal sound, no matter how faint, must never be ignored. In case of an unusual sound, the engine should be immediately stopped and troubleshooting must be carried out.

Incorrect Approach: The engine room is equipped with hundreds of machinery systems. When the power-plant is in operation, sounds from other machinery can suppress an abnormal sound. Even if you hear something unusual from the generator, you may think it’s coming from nearby environment or machinery. Never ignore even the slightest abnormal sound. Take a second opinion and stop the engine for checks.

2. Smoke: When you see smoke coming from or near the generator, it’s high time to stop the generator immediately. No need to offload the generator as the situation has already passed the danger level. Use the emergency stop button provided in a local or remote station. Smoke can be due to friction between moving parts, overheating etc.

Incorrect Approach: PANIC is the first thing that will strike a person when smoke or fire is seen. It might reduce the engineer’s thinking process, which will eventually slow down the approach.

Never panic in such situation. Use the remote start button for the standby generator, which will come on-load almost immediately (normally done through local), and emergency stop the running generator.

3. Unusual Lubricating Oil Parameters: If the lubricating oil temperature has increased beyond normal or the oil pressure has dropped below the adequate level, stop the generator immediately and find out the troubling issue, which might be a dirty lube oil cooler or chocked filter.

Incorrect Approach: If you noticed a drop in pressure, the first thing comes to mind is to change to standby filter. If your standby filter is not primed and put in service in running condition, due to airlock major bearing damages can occur. It’s always better to stop the machinery and then change it to standby filter, only after priming the same.

4. Higher Differential Pressure: Differential pressure is a term used to assess the condition of lube oil filter by providing a pressure measurement before and after the filter. The difference between the before and after filter pressures is displayed by a gauge. If the differential pressure is in the higher range, stop the generator and change to standby filter.

Incorrect Approach: On numerous occasions, it has been observed that the generator is allowed to run even when the differential pressure alarm is sounded during maneuvering. Engineers usually prefer not to take risk of changing the filter in running condition, as it may lead to blackout if the filter does not perform correctly. They thus plan to change it once the maneuvering is over.  However, due to this sometimes the differential pressure increases further and there is a sudden drop in oil pressure, which trips the generator in between maneuvering. It is very much possible to find bearing metal particles when filters are opened for cleaning. This shows that most of the times engineer is aware of the filter problem but fail to see the bigger picture.

5. Overspeed: Generator is a high-speed machinery and over-speeding of generator engine has resulted in explosions and causality in the past. Over-speeding of the generator is caused mainly due to a problem in the fuel system, specifically malfunction of the governor. If the generator is running above its rated speed and still does not trip (Read about overspeed trips here), engineers must stop the generator immediately to avoid a major accident. Crankcase inspection and renewal of bottom end bolts is then to be carried out.

Incorrect Approach: During trial running of generator after overhauling, the governor droop is altered to get required speed as stated in the manual. It may happen that the generator over-speeds due to wrong setting or due to stuck fuel rack during this time. Cases of not checking the crankcase and not renewing the bottom end bolts are common causes which lead to bearing damages.

6: Cooling Water Supply: Cooling water supply is an essential entity to ensure a smooth running of all high temperature moving parts. If there is no cooling water supply due to the failure of pumps, the generator should be stopped immediately to avoid overheating damage.

Incorrect Approach: If there is no cooling water pressure in the line, sometimes engineers try to release air from the purging cock provided near the expansion tank line of the generator. If the water supply is not available (due to the failure of supply pump), it will lead to further increase in the temperature and stopping of the generator at a later stage, resulting in the seizure of moving parts. Always stop the generator first and then do the troubleshooting. Once the generator is stopped due to starvation of water, flywheel should be rotated with lubrication to avoid seizing of parts.

7: Leakage from Pipings: If any leakage is found from the fuel, lube oil or cooling water pipe, it is to be rectified only after stopping the generator. This will allow the engineer to tackle the leakage easily and better maintenance can be carried out.

Incorrect Approach: If there is a small fuel oil or a water leak from any of the pipe connections, tightening of the connection may stop the leak but over-tightening may lead to a sudden increase in the leakage and with high-temperature fuel and water splashing, it can cause a severe burn to the operator skin.

8. Vibration and Loose Parts: Vibration is one of the main causes which increase the wear rate of moving parts. If loose bolts are found or heavy vibration is detected when the engine is running, stop the generator engine immediately and find the cause for rectification.

Incorrect Approach: It is not a common practice to check the tightness of the foundation bolts of the generator and its attached auxiliaries such as turbocharger etc. on ships. It has been found that many shipping company’s PMS do not include the foundation bolts and other bolts tightening checks in the routine.

9. Non-functional Alarms and Trips: During any point of time, if an alarm of the running generator is detected not to be working, then the generator needs to be stopped immediately as there is a possibility that other important alarms and trips are also not working. This can lead to major failure if an accident occurs in the generator.

Incorrect Approach: Ship crew on several vessels have a tendency to ignore alarms which they think are not important. It is many times observed by Port State Control (PSC) that generator alarms and trips are either not working or wrongly set. Such situations will do no good in saving the generator from disaster. Check all the alarms and trips on weekly basis.

10. Water in Oil: Water leaking in oil will decrease the load carrying capacity of the oil and leads to bearing damages. In such cases, the generator must be stopped if the water content is very high. Immediately find the leakage and renew/purify the sump oil before bringing the generator back in operation.

Incorrect Approach: Several cases have been found wherein the generator lube oil tests were not carried out regularly and the generator was allowed to run with water content in the oil. The effect of small amount of water is not immediately seen, but it will corrode and damage important parts of crankshaft and bearings in the long run.

The stopping of the generator is not limited to above points. There can be several other reasons which would require generators to be stopped immediately. However, it is the duty of the engineer to use his expertise and knowledge to avoid any kind of breakdown well ahead of time.

A wise engineer always think of the worst and hope for the best!

Over to you…

Do you know any important sign which suggests the ship’s generator should be immediately stopped?

Let’s know in the comments below.

10 Situations When Ship’s Generator Must be Stopped Immediately appeared first on Marine Insight - The Maritime Industry Guide

There are several automation systems utilized onboard ship to ensure efficient and smooth running of the Machinery. However, machines still fail, mainly because of the lack of knowledge of the crew on that particular system. For this reason it is is very important to install and maintain the system in correct order to avoid any damage to the machinery.

What is Spark Erosion?

Technically, when two current carrying dissimilar metals are in contact, a sparks travels at the point of contact which erodes the small metal by making a cavity.

In a Vessel, different metals are used to building propeller, hull, bedplate, crankshaft, bearing etc. The current from the cathodic protection system is generally present in these parts, which eventually creates the perfect situation for spark erosion.

Even a ship’s hull made up of steel which  is immersed in sea water, small galvanic current flows through anodic area leading to corrosion and erosion.

Effects of spark erosion

To suppress the effect of galvanic corrosion, especially at the stern part of the ship where the propeller is present, an Impressed Current Cathodic Protection system is used. The propeller shafting is earthed to achieve continuous circuit and to avoid malfunction of the same.

When the propeller is at rest, the stern tube, propeller shaft and bearings are in contact with each other. Similarly main engine bearing and journal are in contact with each other, maintaining continuity of the circuit. When the ship is running, due to the rotation of the propeller and lubricating oil film the shaft becomes partially electrical insulated. It may also happen on the tail shaft using non metallic bearing which acts as an insulation.

The propeller at the aft is a large area of exposed metal which attracts protective cathodic current which produces an arc while discharging from the lubricating film. This results in spark erosion of bearings, which can lead to worse situation if lube oil is contaminated with sea water.

If this effects continue for a considerable amount of time, it may lead to overheating of Main engine bearings caused by improper lubrication resulted by cavities from spark erosion. It may also lead to formation of oil mist, emergency shutdown of the engine or in extreme cases crank case explosion.

Reasons for Spark Erosion

Some of the main reasons which results in Spark erosion related problems on ship are

• The shaft earthing arrangement is not working or improperly fitted

• The Cathodic protection current system setting is wrong

• The hull coating is excessive than required which will increase the galvanic corrosion of the shaft

• Slip rings and brushes in the earthing device are worn out

• The contact between shaft and earth device is not clean

It is advisable to use two earthing devices for the shaft of the main engine. One for earthing purpose and the other to connect with the voltmeter for measuring the potential difference between the shaft and the hull of the ship.

The effect of spark erosion will be minimum if the potential difference is below 50 mv.

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How Spark Erosion Can Damage the Main Propulsion Engine of a Ship? appeared first on Marine Insight - The Maritime Industry Guide