Pumping Systems/Valves

Question 1

with reference to Hydraulic systems;

what are hydraulic reservoirs used for and what kind of maintenance is carried out?

Answer 1

Thehydraulic reservoirsare used to store a volume of oil, dissipate heat from the fluid and remove contamination from the system.

As part of maintenance of the hydraulic reservoirs, if any of the following conditions are met…

System has been opened for major work

Oil analysis states excessive contamination

Hydraulic pump fails

the best best practices to follow are:

clean the region under and all around the reservoir in addition to the reservoir’s exterior.

Remove the oil from the reservoir using a filter pump and place it in a fresh container that has never been used to store any other kind of fluid.

Clean the insides of the reservoir by opening the reservoir and cleaning the reservoir with a “Lint Free” rag.

After that, pour clean hydraulic fluid into the reservoir, and then drain the remaining fluid from the system.

Question 2

with reference to Hydraulic systems;

how many types of hydraulic fluid filters are used , what are they and what kind of maintenance is carried out?

Answer 2

There are 2 typeshydraulic fluid filters for hydraulic systems:

pressure filter which comes in collapsible and non-collapsible type and where the latter is preferred.

return filter which typically has a bypass, which will allow contaminated oil to bypass the filter before indicating the filter needs to be changed.

maintenance

Utilizing a cleaning solution and a set of clean rags, thoroughly scrub the filter housing or cover. Using clean hands, remove the old filter from the filter housing, then place the new filter inside the housing or screw it into place. NEVER allow your hand to touch a filter cartridge. Open the plastic bag and insert the filter without touching the filter with your hand. Overall, most hydraulic fluids are not particularly dangerous. However, they are not meant to be touched directly, swallowed, or inhaled. Used hydraulic fluid can contain metal fragments and waste materials collected during the time of use. don’t handle it after it has been used due to these possible contaminants. Skin exposure to used hydraulic fluid can be managed by washing your hands with soap and water but it is best to limit unnecessary exposure to hydraulic fluid as some types are a skin irritant.

Question 3

with reference to Hydraulic systems;

what kind of maintenance is carried out for hydraulic pumps

Answer 3

The pumps must be checked daily, when in service, for any abnormal noises, vibrations and overheating and if and when it is possible for proper flow and pressure. The best maintenance practices is to check and record flow and pressure during specific operating cycles; review graphs of pressure and flow and check for excessive fluctuation of the hydraulic system (usually the maker gives the fluctuations allowed). It is important to note that hydraulic pumps are very sensitive to impurities and their inner working parts are mainly made of brass. Therefore, any kind of system oil contamination must be avoided as will interfere with pump working performance

Question 4

with reference to Hydraulic systems;

what are hydraulic hoses used for and explain what maintenance must be carried out for them

Answer 4

Thehydraulic hosesare designed to allow fluid to flow from one component to another and they are a vital part of keeping hydraulics systems moving. Any type of hydraulic hoses are required to meet certain standards and pressure loads. It is simple to detect problems with your hydraulic hose assemblies if you check the hoses on a monthly basis. These problems could lead to more serious concerns in the future. A marine engineer must ensure that fluid designed temperature and pressure are not exceeded and all system’s safety features and protections are fully operational. Do not disregard the leakages because the presence of any external leakage indicates that something is wrong. Hydraulic oil is expensive on its own, but if there is a significant leak, additional costs will be incurred due to fines from the Environmental Protection Agency as well as the expense of cleaning up the spill. The fact that a machine operator or technician could easily slip and fall on the remnants of a leaky hydraulic system is another significant cause for concern regarding the level of safety that is there. When threaded pipe couplings, valve seals, and flexible hoses burst not only does pressurized hydraulic fluid create a significant risk of fire, but so does the pressurized hydraulic fluid. A marine engineer must learn to identify potential hazards, like cracks, abrasions in the cover, tight bends or twisting. The cover protects the reinforcements (wire or fabric) from weather and any other environmental hazards. If the wire or fabric is exposed, water and debris can adversely affect the reinforcement by either rusting the wire or, in the case of fabric, allowing water to wick into the system and get behind the coupling where it can cause damage.

Question 5

Explain what anti heeling system on a ship is?

Answer 5

The anti heeling system is part of the ballast system. The anti-heeling tanks are located on the port and starboard sides of the ship and are filled and emptied by means of the ballast system. A reversible propeller pump is used in the heeling system. This pump is attached to a pipeline that connects the two heeling tanks. Depending on the control position that has been pre-set, the pump can be started and stopped either from the anti-heeling system control panel located in the integrated control and monitoring system (ICMS) screen displays, located on the bridge. On board, the use of the control panel for the anti-heeling system is the option that is most highly recommended because it enables full access to the system through a menu-driven operator display. When heeling operations are being performed, there will be a lowest level at which the pump will automatically shut off, same as a maximum level that can be reached in any tank. Floats for the highest level are installed in each tank. These are wired up and attached to the monitoring and alarm system. Each tank is equipped with a low level transmitter, which will turn off the pump when the predetermined level is reached. When the pump is running, the system will turn off automatically if the ship’s heel is greater than 8 degrees. During cargo loading and discharge activities, the vessel will be able to stay within acceptable heeling limits thanks to the anti-heeling system. On container vessels, the vessel should not be listed more than 0.5 degree to either side of upright in order to guarantee that containers move freely in the cell guides. However, the loading and unloading of containers can cause the ship to list beyond these limitations. The list can be corrected by moving a quantity of water from the port anti-heeling tank to the starboard anti-heeling tank, or vice versa. Make sure that the anti-heeling tanks are filled with sea water to the correct level before beginning any mode of operation. This means that the combined total of both tanks should be less than 95% of the capacity of one tank. Check to see that the pump, the control panel for the anti-heeling system, and any other system equipment all have access to electrical power. The operation on AUTO mode of the anti-heeling system is only permitted in harbour. The anti-heeling pump may be operated locally in manual mode for maintenance purposes. Push-buttons allow the pump to be started locally, in either the port or starboard flow direction.

The operating modes of the system are as follow:

AUTO: starting and stopping is decided by heel measurement to keep the vessel at a predetermined heel

MANUAL: starting and stopping is controlled by the operator

GOTO: the operator keys in a desired heel and the pump will run until that heel value is obtained

VALVE: the tank valves only are opened to gravitate water between tanks achieving the desired heel correction without starting the pump

LOCAL/COMP: operation of the heeling pumps remotely from the ICMS screen display in the SCC or the bridge.

Question 6

explain what are ant-rolling tanks.

Answer 6

Some vessels are equipped with anti-rolling tank which is fitted to provide a roll damping system to control the rolling of the vessel at sea and is a passive free surface open channel type anti-roll tank. The system is capable of adapting to changes in load and operation conditions by a change in the liquid level, the natural response period of the tank can be adjusted to the roll period of the ship. The system includes a liquid level and roll period indicating system and a phase sensing system to monitor the movement and control the anti-roll tank to assist the crew in achieving the most effective roll stabilization.

The operation of this type of anti-rolling tank consist of the following:

Prior to departure

A. Calculate the solid transverse metacentric height (GMs) without any free surface reduction of any tanks for the anti-rolling tank filled at the maximum operating liquid level.

B. Check whether the calculated GMs is equal or higher than 3.0 meters. If this is the case, continue with 4.

C. If the GMs is less than 3.0 meters, refer to the figure to obtain the correct operational liquid level. Recalculate GMs with the obtained liquid level. Refer again to the figure whether GMs is within the indicated range of GMs. If the GMs should fall on the dividing line between two operational liquid levels, use the higher level.

D. Check whether the corrected GM including the free surface correction of all tanks (including the anti-rolling tank filled to the corresponding operating level) is above all minimum stability requirements. If operating parameters are acceptable fill or adjust the anti-rolling tank to the correct liquid level.

At Sea

A. The tank liquid level/roll period indication system constantly monitors the operational conditions and will automatically alarm to alert the crew if any adjustment of the system is required.

B. In case of emergency, vessel’s stability must be considered carefully. If necessary the tank can be emptied by operating the quick discharge dump valves from the control panel.

C. The tank should be emptied if the GMs is below or above certain values.

D. If the roll period of the vessel is shorter than 16.0 seconds the range of design efficiency is reached. The tank should be operated at the maximum designed operational liquid level.

Question 7

what is water hammering?

Answer 7

Water hammering is a pressure surge caused by a rapid change in flow velocity in the pipeline. This phenomenon is referred to as “water hammering” because the pressure surges are frequently accompanied by a noise that sounds as if the pipeline were being pounded with a hammer.

Question 8

what is the procedure for pumping from engine room bilge wells to oily bilge tank?

Answer 8

The procedure to pump from the engine room bilge wells to the oily bilge tank is, generally, as follow:

Check and ensure that the engine room bilge pump suction strainer is clean.

Check and ensure by taking a sounding measurement that there is sufficient space in the oily water tank for the bilge water, before starting the transfer operation . If the oily water tank is full, bilge water can be transferred to the clean bilge tank.

Open the bilge pump discharge valve to the oily water tank and ensure that all the other bilge pump discharge valves are closed.

Open the bilge pump suction valve to the main engine room bilge system as this connects all the suction points to the bilge pump.

Check the suction strainer on the bilge suction to be pumped and open the suction valve.

Start the bilge pump. Ensure that the bilge pump does not run dry. Usually, bilge pumps have a sea water suction connection which can be used for priming. don’t keep the sea water valve connection open for too long time, as there is a risk of filling the oily bilge tank with too much sea water.

Close the bilge suction valve before the bilge is completely empty to prevent the pump to run dry.

Question 9

what is the purpose of the oily water tank and the clean bilge tank?

Answer 9

The oily water tank acts as the
(separate oil tank/sludge tank) collects oil from the OWS which can then be remove by the sludge transfer pump to be transferred ashore or to waste oil tank/incinerator for evaporation.

Water is removed from the oily water tank and transferred to the clean bilge tank by the bilge pump.

Question 10

with reference to hydraulic systems;

a.) what is the purpose of hydraulic pumps and motors?

b.) what are hydraulic cylinders

Answer 10

a.) The pumps purpose is to essentially move hydraulic fluid around the system. Hydraulic pumps operate by creating a vacuum at a pump inlet, forcing liquid from a reservoir into an inlet line, and to the pump. Mechanical action sends the liquid to the pump outlet, and as it does, forces it into the hydraulic system. Mechanical power is converted into hydraulic energy using the flow and pressure of a hydraulic pump. these pumps work with the use of hydraulic motors. the function of these is to act as a mechanical actuator and convert hydraulic pressure and flow into torque ( twisting force) and then rotation.
Combined with hydraulic pumps, the hydraulic motors can create hydraulic transmissions in other words the flid is able to be sent around the system.

b.) A hydraulic cylinder is a mechanism that converts energy stored in the hydraulic fluid into a force used to move the cylinder in a linear direction. It can be either single acting or double acting. As part of the complete hydraulic system, the cylinders initiate the pressure of the fluid, the flow of which is regulated by a hydraulic motor.

Question 11

what are some Advantages and Disadvantages of Hydraulic Systems

Answer 11

Advantages

A convenient method of transferring power over relatively long distances from, say, a central pump room to remote operating sites in the ship; where necessary, complete local control of operations can be achieved.

Fully variable speed of both linear and rotary motion, with good “inching” capability and smooth take up of load; in all cases power is continuously transmitted whilst speed changes take place.

High static forces or torques can be achieved and maintained indefinitely. Example is of lifting and keeping lifted large weights of cargo.

Complete safety and reliability is assured under the most difficult environmental conditions; overload conditions are safeguarded by using a relief valve to limit maximum output torques or forces.

Significant cost savings as alternative solutions for many requirements.

Disadvantages

It is a messy and therefore the areas around he system may not be always ship shape.

Some high pressure hydraulic systems have caused serious accidents because of high pressure.

Leak in hydraulic system can be the cause of major fires and or explosions.

Question 12

how do hydraulic systems work?

Answer 12

How do hydraulic systems work?

Hydraulic systems work based on the principle of Pascal’s law. Pascal’s law states that pressure applied to an enclosed fluid will be transmitted without a change to every point of the fluid and to the walls of the container. The pressure at any point in the fluid is equal in all directions.The key components in a hydraulic system are – the pump, motor, valves, hoses, filter, and reservoir.

Specifically, here’s how a hydraulic system works:

1.An engine or electric motor powers ahydraulic pump, the hydraulic system.

2.The pump pushes pressurized fluid through the hydraulic system and converts mechanical energy to fluid power.

3.The pressurized fluid goes through various control valves to the hydraulic actuator.

4.Hydraulic actuators consist of either a hydraulic cylinder (linear actuation) or a hydraulic motor (rotary actuation) that converts hydraulic power into mechanical power.

Question 13

with reference to sea water cooling system

what is seawater used for and how is corrosion and scaling controlled?

Answer 13

Seawater is used to provide feed-water to the Evaporators, secondary cooling for the Engine Cooling Circuits and in some cases cooling for the Air Charge Coolers. Seawater is introduced into the ship through open inlets and stored in containing tanks called ‘sea-chests’ within the body of the hull. These cooling duties utilize a variety of Heat-exchanger designs which can become severely fouled due to impurities and contamination in the sea-water supply.

Corrosion and scaling are two issues that can be caused by the dissolved gases (oxygen and carbon dioxide) and salts of magnesium and calcium that are found in sea water. However, because these cooling systems have a high flow that only goes through them once, it is not economically feasible to continuously apply treatment to inhibit scale and corrosion like it is in boiler cooling system and engine cooling system. The easiest way to prevent scaling and corrosion is to make sure that the metallurgy of the heat exchanger is chosen correctly and to keep the temperature of the sea water below
50 ºC at all times.

Question 14

with reference to sea water cooling system

what is the main reason for fouling and how is it prevented?

Answer 14

The presence of micro-organisms that are found naturally in sea water, these are the primary cause of the issue known as fouling, which is related to sea-water cooling system. The Mussel (Mytilus Edulis) and the Barnacle are the two troublesome species that cause the most issues (Balanus Balanoides). These species are extremely numerous all throughout the world, and their spawning seasons change according to the environmental conditions that are present at the time. When the water temperature rises above 10-15 degrees Celsius, spawning activity begins to take place. Because of this, the majority of boats operating in deep sea environments are prone to pollution and fouling. Filters and strainers are able to remove mussels and barnacles after they have reached full maturity; nevertheless, it is the newly produced species, known as veliger, that are the source of the issue. These veliger’s begin their lives in a very small size, making it simple for them to enter the cooling circuit and cause problems. Once they are inside the system’s pipes, they attach themselves to the surfaces utilizing protein fibres that are strong and elastic (Byssus). Once they have attached themselves, they are able to quickly feed and expand. Because of their growing size and population, streams are becoming fouled and blocked more frequently.

The presence of this type of fouling will lead to:

Reduced cooling efficiency
Risk of under deposit corrosion and failure
Risk of cavitation and impingement corrosion
Increased pumping and maintenance costs

Due to the fact that the issue organisms are alive, it is possible, in theory, to eliminate them through the use of a number of different biocide additives or the installation ofMarine Growth Protection Systems (MGPS).
It has been tried to use chlorine, however it has been shown that fully grown species can require 0.2 to 1.0 ppm free chlorine over a period of up to 10 days, which can be difficult to accomplish on a ship at sea. Additionally, fully matured mussels and barnacles have the ability to recognize the presence of chlorine as an irritant. Eliminating mussels and barnacles while they are in their most defenceless stage (as veliger’s) and preventing them from attaching and growing is the most effective strategy for dealing with these organisms. This can be achieved through the consistent use of a biocide and anti-foulant that is specific to the company.

Question 15

The water level in the engine room is rising faster than can be contained by the bilge pump.

a) Describe the immediate action that the EOOW should take. (10)

b) What features are provided in the engine room pumping systems to deal with the situation outlined in Q a). (6)

Answer 15

a) * Raise the nearest alarm, notify the bridge and the Chief Engineer.

• Conduct initial damage control, bearing in mind the following concerns: - Isolation of affected areas; - Protection/shielding of machineries, especially those used for damage/flooding control.
• When the on-scene leader arrives
  (Chief Engineer), start preparing the emergency bilge suction station and any other provided arrangements for dealing with bilge waters.

Open emergency bilge suction valve and try to locate the problem.

Start other circulating system and isolate the leaking pipe, pump or cooler.

Close the inlet and outlet valves of affected system to stop the leak.

b) In addition to the bilge main and direct suctions to different pumps, a direct emergency bilge suction system is used connected to the main circulating pump (or the largest available independent power-driven pump) leading to the drainage level of the machinery space and fitted with a emergency suction valve shall be provided in the machinery space. It is a large non-return valve whose suction pipe draws from the tank tops with a strum-box and pipes which should be 2/3’s of system pipe diameter.

Question 16

State EIGHT actions the Engineer officer of the Watch would take on
acknowledging unexpected high level engine room bilge alarms, in both port and starboard bilge wells?

Answer 16

line up the bilge system valves and use the bilge pump to pump the bilge water

monitor the bilge pump suction and discharge pressure to ensure correct operation

ensure the bilge wells are going down monitor flow rate and rise

contact C/E and to get assistance

if the bilge system isn’t coping with the water ingress rate then with the chief engineers permission emergency direct bilge injection system can be used

line up the system to discharge the bilge water and start the largest pump in the engine room to use for system

identify the source of leakage and if possible stop the flooding

isolate the flooding to the bilges

Question 17

with the aid of a system drawing describe a central cooling system?

Answer 17

See EOOW ORAL/IAMI Sketch Pack for System drawing

large sea water cooled heat exchangers, one in operation the other standby, are the central coolers. these have excess cooling capacity to allow for fouling. a controlled bypass of the fresh water to be cooled maintains it at steady temperature of 35Deg Celsius up to a max sea water temperature of 33. sea water temperature above 33 will result in an increase in FW temperature. the system is divided into low and high temp zones. low temp zone has the coolers, which can be arranged in different way to suit requirements. automatic bypass valves are arranged across each cooler unit that controls the upstream water pressure keeping it constant irrespective of the number of coolers in use.

Question 18

what are the advantages of a central cooling system?

Answer 18

1. reduced maintenance, due to FW system having treated water circulating. the cleaning of the system and component replacement is reduced to a minimum
2. fewer salt water pipes with attendant corrosion and fouling problems
3. with titanium plate heat exchangers used, cleaning of the coolers is simplified and corrosion reduced.
4. the higher water speeds possible in FW system result in reduced pipe dimensions and installation costs
5. number of valves made of expensive material is reduced. also cheaper materials can be used throughout the FW system without fear of corrosion/erosion problems
6. with an constant temp being maintained, this gives stability and economy of operation of the machinery, for example, no cold starting since part of cooling system will be in operation and therefore reduced cylinder liner wear.

Question 19

With the aid of a sketch describe the function of a bilge injection system.

Answer 19

SEE EOOW ORAL/IAMI Sketch Pack

The bilge injection valve sketched above is provided for use in the event of serious flooding in the machinery spaces. By closing the main injection valve and opening up the bilge injection valve, the largest pump (or pumps) in the engine room draw directly from the lowest point in the space. This removes large quantities of of water. A doubler plate is welded to the skin, and machined usually after welding operations, the chest flange being bedded to the doubler and then studded in place. The joint is either spigot and jointing compound, or flat with a joint of canvas and red lead putty. The diameter of the bilge injection valve is at least two thirds of the diameter of the main sea inlet. Valve spindles should be clear of the engine platform and valves and operating gear require regular examinations and greasing, with cleaning of strum or strainer.

Question 20

with reference to MGPS

how can the effectiveness of the system be evaluated?

Answer 20

The effectiveness of the system can only be evaluated through examination, and the manufacturers recommend that if after 6 months of operation, the opportunity to examine a strainer, length of pipe, or heat exchanger comes, that this to be done.
If there are symptoms of infestation, increase the current to each anode in the relevant marine suction filter by a maximum of 0.2 amps. If there is no evidence of an infestation, the current can be lowered by up to 0.2 amps. This routine should be repeated at regular intervals, with the current adjusted accordingly. The anodes have a life expectancy, usually, of 2.5 years. Routine inspection of the anodes and sea strainers will show when replacement is required.

Question 21

what is the procedure for operating MGPS system?

Answer 21

The procedure for operating the system

Check that the sea water system is operating and that sea water is flowing through the strainer, either the high or low strainer.

Ensure that the selector switch is set to the port or starboard sea suction strainer as required, but it may also be set to the DUAL position if both sea suctions are open.

Check if the main breaker switch is set to the ON position and that the POWER ON lamp is illuminated.

Set the selector switch to the AUTO position.

The protection system timer will start, usually, with the OFF period. When the timer enters the ON period, the indicated currents for the chlorine (MMO) electrodes and the copper electrode should be checked and adjusted if necessary, by means of their individual potentiometers. The timer may be set for off and on periods to suit conditions.

If you want to switch off the system, after stopped ensure that the sea water flows through the strainer for a few minutes to ensure any copper, chlorine or hydrogen gas is removed from the vessel.

Question 22

what are the precautions when operating MGPS system?

Answer 22

There are some precautions that need to consider when operated by the responsible engineer and few of these, but not limited to, are mentioned below:

Gases are released at the electrodes; chlorine at the anode and hydrogen at the cathode. It is essential that sea water is flowing over the electrodes whenever the electrodes are supplied with current, in order to flush these gases away. If the sea water pumps are switched off the power supply to the electrodes must also be switched off. If this is not the case the gases can build up resulting in an explosion.

The copper electrode and the chlorine (MMO) electrode currents must be set to suit water flow which is influenced by the sea water temperature as a higher sea temperature requires a higher water flow to give the correct cooling capacity
.
The current settings should be set according to the sea water flow for optimum performance and efficiency. The setting pro rata is given on a table supplied by a manufacturer or shipyard.

Care must be taken to ensure that the current at the electrodes is set correctly for the water flow rate. Excessive current will result in rapid wear of the electrodes. Too high a current at the copper electrodes will cause heavy deposits on the sea suction filter element resulting in flow restriction and even greater deposits. The higher the current the shorter the anode life.

If the vessel is in fresh or brackish water, the system should be switched off as missing sea water will make it inoperable and the control system may be unable to reach the recommended current setting causing the alarm to activate.

During maintenance, before opening the sea chest strainer, make sure that the system is switched off and that the strainer casing is pressure less and water is drained. It happens very often that the sea chest valves are not properly holding, thus making nearly impossible to open the filter and posing a very high risk of flooding if is not handled correctly.

Question 23

with reference to MGPS system

explain what biofouling is?

Answer 23

Biofouling is the accumulation of aquatic microorganisms, plants and animals on surfaces and structures immersed in or exposed to the aquatic environment. Aquatic organisms may be transferred to new locations and can be harmful and invasive in locations where they do not naturally occur. They can threaten marine environment, human, animal and plant life. Once invasive aquatic species are established in a new location or habitat, they are often impossible to eradicate.

The anti-biofouling system suppresses the growth of micro and macro-fouling on seawater immersed surfaces. The system is designed to safeguards the internal surfaces of enclosed seawater systems, such as pipework, valves, pumps, heat exchangers, and filters.
Marine biofouling and corrosion can occur in two ways:

Barnacles, mussels, hydroids, and other organisms can cause macro-fouling, which reduces water flow, blocks piping, and increases corrosion.

Micro-fouling is made up of bacterial slime, micro-algae, and other organisms that impair the heat transfer efficiency of heat exchanger surfaces.

Corrosion can be accelerated in two main ways:

When biofouling forms on a metal surface, the oxygen content underneath the fouling layer decreases. In areas of metal exposed to oxygenated sea water, this layer becomes anodic. As a result, pitting corrosion occurs beneath the fouling.

Corrosion produced by bacterial activity. Sulphate reducing and iron bacteria are organisms that induce corrosion by their biological activities or metabolic by-products. Such bacteria thrive in low-oxygen environments, such as behind a layer of aerobic fouling species or in deaerated water like that found in oil storage tanks and bilge wells.

Question 24

explain what is What is Marine Growth Protection System (MGPS) and its purpose?

Answer 24

For a variety of reasons, ships rely on the seawater in which they move and one of the primary functions of seawater is to keep the engine and other sections of the ship cool while they are running. The utilized seawater is then discharged back into the sea, and additional seawater is taken in, resulting in a continual flow of salt water exchange between the ship and its surrounding aquatic environment. Despite its benefits, the negative is that seawater contains marine species (both macro and micro), some of which are visible to the naked eye and the majority of which are not. Marine organisms are deposited on the ship’s surface as seawater travels through the different pipelines and sections of the engine. Over time, the deposit accumulates, lowering the effectiveness of the ship’s systems and, in severe situations, choking the entire cooling system of the ship’s leading to the engine’s failure.

There are different systems and methods, with different type of electrodes, which are working in pair and the anodes employed are marine growth (MG) type and trap corrosion (TC) type. In general, the system is based on the simultaneous electrolytic generation of copper ions and chlorine, which reduces the levels of existing macro- and micro fouling organisms while preventing the growth of new ones. All existing and proposed environmental regulations are compliant with the copper and chlorine concentrations used.

The most used and known system on-board vessels is Cathelco, K.C. Ltd, Petreco.

The MG anodes are manufactured from copper and release ions during electrolysis which combine with those released from sea water form an unsuitable environment for entering organisms. The TC anodes are, usually, manufactured from aluminium for use in a system with predominantly steel pipes. The aluminium anodes in reaction with sea water will form aluminium hydroxide who will act as anti-corrosive barrier on the pipework. Lately, due cutting cost policy all over the places, the TC anodes are mixed metal oxide (MMO) type.
The copper and MMO electrodes are the anodes in the electrical circuit, which is set up between the strainer body and basket and these act as the cathode to the anodes. The current supply to the electrodes is controlled by thyristor current control modules, which are located in the control panel. The control panel also houses the supply transformer and surge suppression circuits, together with all instruments and controls.

A pulse dosing technique is used for ensuring the correct conditioning of the sea water. This is achieved by switching the power supply to the electrodes on and off using timers; typically the power supply is on for 3 minutes and then off for 3 minutes. The current supplied to each electrode is adjustable at the current setting potentiometer. The controller has facilities for operating the port or starboard electrodes or both sets of electrodes as necessary. Under normal circumstances the system is set for automatic operation and the current at each electrode is controlled by the controller.

Question 25

whats the purpose of a lubrciation system?

Answer 25

The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in the engine. Its main function is to enable the formation of a film of oil between the moving parts, which reduces friction and wear. The lubricating oil is also used as a cleaner and in some engines as a coolant.

Large slow-speed diesel engines are provided with a separate lubrication system for the cylinder liners. Oil is injected between the liner and the piston by mechanical lubricators which supply their individual cylinder, A special type of oil is used which is not recovered. As well as lubricating, it assists in forming a gas seal and contains additives which clean the cylinder liner.

Question 26

explain how a lube oil system works?

Answer 26

Lubricating oil for an engine is stored in the bottom of the crankcase, known as the sump, or in a drain tank located beneath the engine. The oil is drawn from this tank through a strainer, one of a pair of pumps, into one of a pair of fine filters. It is then passed through a cooler before entering the engine and being distributed to the various branch pipes. The branch pipe for a particular cylinder may feed the main bearing, for instance. Some of this oil will pass along a drilled passage in the crankshaft to the bottom end bearing and then up a drilled passage in the connecting rod to the gudgeon pin or crosshead bearing. An alarm at the end of the distribution pipe ensures that adequate pressure is maintained by the pump. Pumps and fine filters are arranged in duplicate with one as standby. The fine filters will be arranged so that one can be cleaned while the other is operating. After use in the engine the lubricating oil drains back to the sump or drain tank for re-use. A level gauge gives a local read-out of the drain tank contents. A centrifuge is arranged for cleaning the lubricating oil in the system and clean oil can be provided from a storage tank. The oil cooler is circulated by sea water, which is at a lower pressure than the oil. As a result any leak in the cooler will mean a loss of oil and not contamination of the oil by sea water. Where the engine has oil-cooled pistons they will be supplied from the lubricating oil system, possibly at a higher pressure produced by booster pumps, e.g. Sulzer RTA engine. An appropriate type of lubricating oil must be used for oil-lubricated pistons in order to avoid carbon deposits on the hotter parts of the system.

Question 27

describe what are hydraulic systems?

Answer 27

The open-loop circuit takes oil from the tank and pumps it into the hydraulic motor. A control valve is positioned in parallel with the motor. When it is open the motor is stationary; when it is throttled or closed the motor will operate. The exhaust oil returns to the tank. This method can provide smooth changes in motor speed. The live-line circuit, on the contrary, maintains a high pressure from which the control valve draws pressurised oil to the hydraulic motor (in series with it), as and when required. In the closed-loop circuit the exhaust oil is returned direct to the pump suction. Since the oil does not enter an open tank, the system is considered closed. Low-pressure systems use the open-loop circuit and are simple in design as well as reliable. The equipment is, however, large, inefficient in operation and overheats after prolonged use. Medium-pressure systems are favoured for marine applications, using either the open or closed circuit.

Question 28

function of a cock?

Answer 28

A cock is used in small-bore pipework and is joined to adjacent pipework by a compression coupling. A cock can restrict or close an internal passage by moving a central plug, usually by an external lever.

Question 29

describe the construction and use of a globe valve?

Answer 29

A globe valve has a somewhat spherical body enclosing the valve seat and valve disc. Flanges are provided at either side for connecting to adjacent pipework, and internal passages guide the liquid flow through the valve seat. Liquid flow is always arranged to come from below the valve seat so that the upper chamber is not pressurised when the valve is closed. A gland with appropriate packing surrounds the spindle where it leaves the valve bonnet. The upper part of the spindle is threaded and passes through a similarly threaded bridge piece. A circular handwheel is used to turn the spindle and raise or lower the valve disc. The valve disc and seat are a perfect match and may be flat or, more commonly, mitred. The material for both is often provided with a very hard stellite coating. Globe valves also exist in a right-angled form where the inlet and exit flanges are at 90° to each other. Unlike the gate valve, globe valve can be used for regulating flow or pressures as well as complete shutoff of flow. It may also be used sometime as a pressure relief valve or as a check valve.

Question 30

what are non return valves and check valves used for?

Answer 30

Check valves are installed in pipelines to prevent backflow. A check valve is basically a one-way valve, in which the flow can run freely one way, but if the flow turns, the valve will close to protect the piping, other valves, pumps.

non-return valve allows a medium to flow in only one direction and is fitted to ensure that the medium flows through a pipe in the right direction, where pressure conditions may otherwise cause reversed flow.

Question 31

what’s the function of gate valves?

Answer 31

Gate valves are used to isolate specific areas of the water supply network during maintenance, repair works, new installations, as well as to reroute water flow throughout the pipeline. A gate valve should be fully open or closed; it is not suitable for flow control.

Question 32

function of quick closing valves?

Answer 32

Quick closing valves are fitted to settling and service tanks within the machinery spaces, boiler room and the emergency generator space so that in the event of an emergency such as a fire, they may be safely closed from a remote location to prevent the fuel in the tank from feeding the fire. Oil tank suction valves are arranged for rapid closing from a remote point by the use of quick-closing valves. The collapsing of the ‘bridge’ results in the valve closing quickly under the combined effects of gravity and an internal spring. A manually operated wire or a hydraulic cylinder can be used to collapse the bridge.

Question 33

what are valve chests?

Answer 33

Valve chests are a series of valves all built into a single block or manifold. Various arrangements of suction and discharge connections are possible with this assembly.

Question 34

what are mud boxes?

Answer 34

Mud Boxes are a coarse stariner (filter) device which installed in suction pipes aboard vessels to protect pumps against large solids.

Question 35

explain what is meant by water hammer and what a steam trap does?

Answer 35

A steam trap does as its name implies and permits only the passage of condensed steam. It operates automatically and is situated in steam drain lines. Various designs are available utilising mechanical floats which, when floating in condensate, will enable the condensate to discharge. Other designs employ various types of thermostat to operate the valve which discharges the condensate. An expansion piece is fitted in a pipeline which is subject to considerable temperature variations. One type consists of a bellows arrangement which will permit movement in several directions and absorb vibration (Figure 6.18). The fitting must be selected according to the variation in system temperatures and installed to permit the expansion and contraction required in the system. Drains are provided in pipelines and usually have small cocks to open or close them. It is essential that certain pipelines are drained regularly, particularly in steam systems. When steam is admitted to a pipeline containing a reasonable surface of water it will condense and a partial vacuum occur: the water will then be drawn along the pipe until it meets a bend or a closed valve. The impact of the moving water in the pipework will create large forces known as ‘water hammer’, which can result in damage to pipework and fittings.

Question 36

With reference to domestic FW Distribution system what is meant by charging and how is this carried out?

Answer 36

Charging: This is the process of filling the hydrophore tank with water and compressed air to achieve the desired pressure range.

To charge the system, follow these steps:

• Close the outlet valve of the hydrophore tank.
• Start the pump in manual mode and watch the level gauge on the tank.
• Once the water level reaches about 70% of the tank capacity (some tanks have markings on the level gauge), charge the tank with compressed air using an air compressor or an air bottle.
• Stop charging when the pressure gauge on the tank reaches about 5 bar (some tanks have markings on the pressure gauge).
• Put the pump in auto mode and open the outlet valve of the tank.
• Monitor and check the pump cut-in and cut-out pressures on the pressure switch.

Question 37

what maintenance is required for marine hydrophore system (domestic FW system)?

Answer 37

Some of the tasks involved in maintaining marine hydrophore systems are:

Cleaning: This is the process of removing dirt, dust, oil, grease, rust, or corrosion from the system’s components, such as the tank, the pump, the valves, and the pipes. Marine engineers must use suitable cleaning agents and tools to clean the system thoroughly and carefully.

Inspecting: This is the process of examining the system’s components for any defects, faults, or damages that may affect their function or performance. Marine engineers must use visual inspection, as well as instruments such as callipers or pressure testers to check the condition and functionality of the components. They must also check the alignment, balance, and lubrication of the moving parts.

Lubrication and Pump Maintenance

Lubricate pump components as per the manufacturer’s recommendations.

Check the condition of pump seals and gaskets and replace them if they show signs of wear.

Control System Testing

Test the control system to ensure it functions correctly.

Verify that pressure switches are set to the appropriate pressure levels.

Alarms and Safety Measures

Ensure that any alarm systems associated with the hydrophore are functioning correctly.

Test emergency shut-down procedures in case of system malfunctions.

Question 38

With the aid of a system drawing describe the domestic freshwater system.

Answer 38

See domestic FW system drawing

Domestic freshwater system is designed to maintain consistent water pressure on vessels, ensuring a supply of fresh water for domestic purposes but also to be used for operational purposes for various systems on the ship like for example the purifiers and the jacket cooling water system. The system consists of a hydrophore tank, valves, pressure switch, pressure gauge, relief valve, air vent valve and two automatic pumps for supplying the liquid, which is pressurised by compressed air. The compressed air provides the head or pressure to supply the water when required. The pump is started automatically by a pressure switch which operates as the water level falls to a predetermined level.

Fresh water supplied must meet purity standards. Water produced from most evaporator/distillers will not meet these standards and must be treated to ensure it is biologically pure and neutral or slightly alkaline. The water is sterilised by an excess dose of chlorine provided as hypochlorite tablets. It is then dechlorinated in a bed of activated carbon to remove the excess chlorine. Any colour, taste and odour which was present in the water will also be removed by the carbon. Excess chlorine is originally applied to ensure that complete sterilisation occurs.

• The hydrophore tank is a pressurized reservoir that stores water and compressed air, to maintain a constant pressure in the water supply system. The tank can store water under pressure, ready for distribution.
• The pumps are used to fill the tank with water and to deliver water to where it’s needed. The pumps transfer water from the freshwater tank and then supply it to hydrophore tank here its pressurized.
• The pressure switches are used to control the start and stop of the pumps according to the pressure in the tank. pressure switch controls the pumps, maintaining the desired pressure level within the pressure tank. When water pressure drops below the set level (due to water consumption), the pump activates to replenish the pressure in the tank.
• The valves are used to regulate the flow of water and air in the system.
• The gauges are used to monitor the pressure and level of water and air in the tank.

Question 39

Sketch and describe a bilge system?

Answer 39

A bilge system is a piping system installed on-board a vessel for the purpose of removing water that accumulates in enclosed spaces (holds, machinery spaces, cofferdams) as a result of condensation, leakage, washing, or fire fighting. It is also capable of controlling flooding in the Engine Room as a result of minimal piping system damage. Bilge wells are fitted with the float operated level alarms to draw engineers’ attention in case of high levels in the bilges. Routinely, the engine room bilges are transferred with the help of Engine Room Bilge Pump to what is known as Bilge Holding Tank. This tank is fitted with the heating arrangements to facilitate the efficient separation of oil and water. Such arrangements are normally steam operated coils inside the tank. At some point the contents of the Bilge Holding Tank need to be processed with the help of an OWS which is a type of a filtering equipment. The Bilge Separator Service Pump (usually a positive displacement type) is utilised to feed the OWS.

The vessel’s bilge system consists of three main sub-systems:

• Engine room bilge system
• Cargo hold bilge system
• bow thruster bilge system

The engine room bilge system and cargo hold bilge system are interconnected and an isolation valve is fitted between these two systems. This isolation valve should normally be closed and sealed and seal recorded into engine room seal log book.

The bilge system contains three pumps

• The engine room bilge pump
• The cargo bilge pump
• The fire and general service pumps

Under normal operating conditions the engine room bilge pump is used to pump from the engine room bilge main to either the clean bilge water tank or the oily water tank. Bilge water from the engine room system can be discharged overboard, while vessel is under way, only via the oily water separator. The cargo bilge pump is used to pump from the cargo hold bilge main to the cargo bilge tank if the ship is designed as such. If there is no designated cargo bilge tank, the bilge can be pumped directly overboard after has been visually checked for presence of oil, otherwise should be pumped into engine room bilge tank via interconnection valve. The bow thruster bilge system is operated by an ejector, which is driven by water, the driving water being supplied from the fire and wash deck system.

The engine room bilge pump is, usually, of a self-priming type which can draw water from the various bilge suctions via the engine room bilge system and discharge to the oily water tank or clean bilge tank. It can take, also, suction from oily bilge tank, clean bilge tank, cofferdams, engine pit, void spaces, stern tube cooling tank etc. In general, all the bilge pump suction points are connected to the bilge pump via the engine room bilge system, except for the clean bilge tank, the oily water tank and the oily water separator. The engine room bilge pump is equipped with a suction strainer and, on modern vessels, the pump motor can be set to stop automatically if the pump runs dry. The pump can be stopped locally or from the shore connection stations on main deck close to the bilge & sludge shore discharge manifold.

Under normal operating conditions the cargo hold bilge system is served by the cargo bilge pump which is, usually, a positive displacement pump but the pump suction is also equipped with a priming unit because of the length and large volume of the cargo hold bilge system. The pump will draw water from the various hold bilge suction points via the forward and aft cargo hold bilge systems and discharge to the cargo bilge holding tank or directly overboard.

The fire and general service (GS) pumps are vertical centrifugal pumps and each pump is equipped with a priming unit. A cross-connection line is fitted between the pump suction and discharge and this line is arranged to ensure that bilge water cannot be discharged into the fire and wash deck main. The bilge system, especially the cargo hold bilge system must be periodically pressure and vacuum tested (6 monthly period) in order to check the valve proper sealing and pipe integrity. Failure to do so can result in cargo hold flooding and damaging of cargo. Usually, cargo hold bilge wells are equipped with non-return flaps which prevents the water back flow into the bilge wells. Checking the integrity of these flaps is one of the reason of the system pressure test that must be periodically done. The vacuum test is done in order to check the remote butterfly valves are sealing properly. The fire and general service pumps can only discharge water overboard or to the fire and general service system. These pumps should only be used to pump bilge water in an emergency.

Question 40

Sketch and describe a ballast system?

Answer 40

The function of the ballast system is to pump to and empty all spaces in the ship in which ballast water can be supplied. The suction pipes for the ballast system will be completely separated from the bilge system. The ballast system can also be used for other purposes in emergencies, such as supplying water to the fire main. The ballast tanks holds water, which is used as ballast to provide stability for a vessel. Using water in a tank provides easier weight adjustment than the stone or iron ballast used in older vessels. It also makes it easy for the crew to reduce a vessel’s draft when they enter shallower water, by temporarily pumping out ballast. Ballast water taken into a tank from one body of water and discharged in another body of water can introduce invasive species of aquatic life. The taking in of water from ballast tanks has been responsible for the introduction of species that cause environmental and economic damage.

The ballast system is arranged to ensure that water can be drawn from any tank or the sea and discharged to any other tank or the sea as required to trim the vessel. Combined or separate mains for suction and discharge may be provided. Where a tank or cargo space can be used for ballast or dry cargo then either a ballast or bilge connection will be required. The system must therefore be arranged so that only the appropriate pipeline is in service; the other must be securely blanked or closed off. Where tanks are arranged for either oil or ballast a change-over chest must be Fitted in the pipeline so that only the ballast main or the oil transfer main is connected to the tank.

The segregated ballast tanks (SBT) are dedicated tanks constructed for the sole purpose of carrying ballast water on oil tanker ships. They are completely separated from the cargo, and fuel tanks and only ballast pumps are used in the SBT. The Segregated ballast tanks avoid any chances of mixing oil and water which usually happens when cargo holds are used to carry ballast water.

Clean Ballast Tanks (CBT) Oil tankers may travel without carrying cargo in its holds which may lead to stability issues. Especially in bad weather. Hence, the cargo holds which carried oil in the last voyage are cleaned and then filled with clean ballast water.

Question 41

what are the common problems that occur in bilge system and their causes (reasons for this)?

Answer 41

Some of the common problems that can occur in a vessel’s bilge system are:

 Clogging and Blockages: One of the most frequent issues in bilge systems is clogging and blockages in the bilge pump and associated pipes. Accumulated debris, dirt, or even marine life can obstruct the flow of water through the system, leading to reduced pump efficiency or complete failure.

 Bilge pump not working: Bilge pump failures can result from various causes, such as electrical malfunctions, worn-out components, or impeller damage. A dysfunctional pump can lead to excessive water accumulation within the vessel, risking its stability and safety.

 Float Switch Malfunction: When bilge pump is running on AUTO mode, float switches are essential components that trigger the bilge pump to activate when water levels rise. Malfunctioning float switches can lead to either constant pump activation (even when unnecessary) or failure to activate when needed.

 Leaks and Cracks: Leaks in the bilge system’s piping, hoses, or pump housing can contribute to the accumulation of water in the bilge area. Corrosion, wear, or cracks in these components can compromise their integrity and cause leaks.

 Electrical Issues: Given the reliance on electrical components in modern bilge systems, issues like corroded wiring, faulty connections, or blown fuses can disrupt the proper functioning of the system.

 Inadequate Maintenance: Neglecting regular maintenance can lead to the deterioration of pump performance and other system components. Lack of maintenance increases the likelihood of encountering issues over time.

 Bilge alarm sounding: This can indicate that there is excessive water accumulation in the bilge due to leakage or damage.

 Bilge water contaminated: This can be caused by oil, fuel, chemicals, or other substances that leak or spill into the bilge. This can pose a serious environmental and safety hazard, as well as damage the bilge system components.

Question 42

Explain how ballast water treatment is carried out

Answer 42

Ballast water treatment – when the tanks are filled and when they are emptied, the ballast water is subjected to mechanical, physical and chemical treatment. There are a variety of ways in which water can be heated or subjected to UV radiation or ultrasound depending on the manufacturer, but the sediments are separated by means of filters. When using ballast water treatment system, prior to ballasting operations, the BWT unit lamps commence a start-up sequence at which time the units are cooled by sea water. The incoming ballast passes through the filter which performs the function of removing larger organisms and particles, after the filter, the ballast water passes through the UV or chemical injection units which treat the water to the required IMO standard before entering the ballast tanks. On completion of ballasting, an automated sequence flushes the treatment unit with fresh water, following this a Cleaning cycle commences to clean the unit, which takes approximately 15 minutes. The cleaning cycle may also be operated manually from the local control panel. During de-ballasting, the main difference to the ballasting procedure is that the filter is bypassed because the water would already have been filtered during ballasting. During the discharge process, water from the tanks is again passed through the UV or chemical injection units to destroy any organisms that may have formed during the time the ballast water has remained in the tanks. Ballast system is normally operated by vessel Chief officer or one of the deck officers during their watch keeping under Chief Officer supervision and the engine room should be informed when using the system. Under normal circumstances no more than one pair of ballast tanks (port and starboard) should be partly filled at any one time in order to prevent stability problems due to the effect of slack tanks. Tanks not currently being filled or emptied should be filled or empty. Check the quantity of ballast water to be removed from the particular pair of tanks. Water should normally be removed from the port and starboard ballast tanks at the same time with heeling being controlled by the anti-heeling system.

Question 43

Explain what ballast system and anti-heeling system is used for

Answer 43

Ballast system

The ballast system utilizes water tanks positioned in the double bottom, beneath the ship’s main deck. In order to keep the ship’s draught and trim proper, to provide maximum stability, and to keep the ship’s stress and bending moments within acceptable limits, water is added to or removed from the ballast tanks. One tank or pair of tanks should never be partially filled (slack) at any given moment, as slack tanks provide a free surface effect that is detrimental to stability. Ballast systems consist of tanks with pipes and pumps that may be filled or emptied in order to alter the ship’s mass and hence its draft. For ballasting operations, the ballast pumps can draw suction from the main sea water main crossing pipe in the engine room. As part of de-ballasting procedures, the ballast pump discharges directly overboard. The ballast system is controlled from the ship’s control centre panel which enables the pumps to be started and stopped and ballast system valves to be opened and closed remotely. Usually the valves are hydraulically operated and all of them are normally located outside of the respective ballast tanks which allows maintenance and inspections to be carried out on all of the valves without having to enter a tank. All ballast and de-ballasting operations for each tank must be entered into the Ballast Log Record Book, stating date, ship’s position, temperature, specific gravity, pumped quantity and tank quantity. The International Convention for Control and Management of Ship’s Ballast Water and Sediments applies to all vessels that carry ballast water.

If there is no ballast system

• The propeller may not fully immerse in water, affecting the engine efficiency of the ship
• The ship may list or trim as the cargo capacity of the ship is not fully reached
• The shear and torsion loads on the vessel may increase the stresses on the ship structure, leading to bending moments and slamming
• The vessel may face issues of dynamic transversal and longitudinal instability

Anti-heeling system

Heeling systems on the other hand simply recirculate the ship’s ballast water to maintain a ship’s heel or trim. Heeling tanks are partially filled with water and are used to adjust the heel of the ship during loading and unloading operations. Water is transferred from the port heeling tank to the starboard heeling tank, or vice versa, in order to keep the ship in the upright position using a dedicated anti-heeling pump system. The heeling tanks are filled and emptied by way of the ballast pumping system. In the event of a failure of the anti-heeling system, the ballast pump is used to transfer ballast as required between the port and starboard heeling tanks. After an incident, the heeling system must be able to move huge amounts of water in a short period of time and give a heeling compensation