Fuel Injection and Fuel Pumps Flashcards
Explain What the term bunkering means?
It refers to the procedure of taking on all types fuel and lube oil, it also applies to water in the unlikely event of a ship having to take on water instead of being able to produce it. Its important that a ship doesn’t run out of fuel. Fuel consumption calculation are made by the chief engineer who will determine how much fuel is required based on these calculations and then what port the ship has to take on fuel. Choice of bunkering port is important because it has to fit in with the ships operations ad it must also be a cost effective port that the ship calls at. Research is carried out to reveal the cost of all different grades of fuel, if a bunkering facility isn’t available at a port then its possible to do it by bunker barge. When bunkering its important that ship receives correct amount and the right specification fuel due to cost related reasons and that the fuel has to last until next bunkering operation but most importantly if fuel isn’t correct specification ship is at the risk of breaking down at sea.
What are some important points about bunkering?
Before the bunkering all ships officers should be aware that bunkering is due to take place and all engineering staff should be aware of their roles and responsibilities.
Ships engineer must ensure that the hoses supplied are free from any defects
Ships engineer to be present when the final flange from the hose is connected to the ships pipework, including flange joint
All holes in final flange should have a suitably tightened nut and bolt
All deck scuppers should be blocked off and there should be sufficient absorbent material available to soak up any oil spill
Savills under the pipework flanges should be intact
Hoses should have sufficient slack and be supported so that there is no weight on the flange
Good communication should be set up between the bunker station or barge as well as between the bunker station and ships engineering staff controlling internal oil pathways
Fuel samples should be kept on-board for at least 12 months and ship should have a system in place to keep track of retained samples
When bunkering HFO it must be kept at temperature suitable for pumping and storage. If oil cools down wax can form, which may clog up filters and effect operation of pumps. Steam plant should therefore be in service to maintain temperature of fuel
Record to be kept about which storage tanks are holding bunkers loaded in which port.
Also its good practice not to mix bunkers from any one place. This means if defective fuel is loaded there is little cross contamination as possible.
Special care must be taken in cold climates to ensure that the correct temperature is maintained
With different grades of fuel it will be important for engineers to keep track of where the different oil types are stored. Ships may have LSMDO (low sulphur marine diesel oil), IFO (intermediate fuel oil) and HFO (heavy fuel oil). these oil can be mixed in storage tanks and will only come into contact with each other for short periods during a fuel change over.
What is the purpose of settling tanks?
Settling tanks use the process of gravity separation, to separate the water and particles of dirt out of oil and fuel. When the oil is allowed is allowed to stand undisturbed in the tank, elements of higher relative density than oil gravitate to the bottom of the tank where they are discharged periodically through a manually operated sludge cock. The process of separation in a settling tank can be speeded up to a certain point by heating the tank contents. For this steam heating coils are generally used but care must be taken not to heat the oil to a too high temperature. SOLAS requires that marine fuel have a flash point of 60℃ but classification societies recommend a temp of above 45℃, which preserves the quality of any blend. Ideal temperature for heavy oil in a bunker is 50 to 55℃. there need to be sufficient heating capacity to raise the heavy fuel oil temperature ready for final preparation phase prior to use by the main engine.
What are the three processes used to clean fuel and lube oil?
On-board the ship there are three processes that are used to clean fuel and lube oil, they are gravitation, filtration and centrifugal purification.
Sketch a typical arrangement of a oil settling tank showing the internal and external fittings and then provide a brief description for each one.
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Sludge valve or cock: used for draining water and sludge from the bottom of the tank. It must be self closing, otherwise if for whatever reason it was left unattended, a dangerous situation could arise whereby the tank contents could be drained into the oily bilge or sludge tank
Dumping valve: this fitting can be used in the event of fire to dump the oil from an elevated settling tank to a double bottom tank, which could possibly be below the level of the fire.
Exhaust steam: from heating coils this would be led to a steam trap, which ensures maximum utilisation of the heat content in the steam, then to an observation tank where any defect in the pipe work can be diagnosed due to oil crossing over into the steam heating circuit.
Overflow pipe: this is an important feature of the tank that stops it from being over pressurised and prevents flooding by leading excess oil into an overflow tank. An important note is if a tank is filled up to its max then when the fuel is raised in temperature it will expand. This leads to oil being forced up the overflow pipe and leads to oil spills. Therefore always leave room in the tank for the oil to expand.
Sounding pipe: this is a tube extending from a platform above the tank through the top of the tank to the bottom. At the foot of the tube are two important features. The first one being a hole so that the liquid in the tank can enter the pipe and the level in the pipe and the tank can then be measured. The second feature is a flat metal plate placed at the bottom of the pipe, which is called a striker plate and its there to take the force of the weight of the end of the sounding tape hitting the bottom. The weighted cock (near cap) on the top of the sounding pipe is important and should be checked for correct operation by the watch-keeper. The reason being is that the weight ensures that the cock is closed following each use because it restricts any liquid travelling up the sounding pipe and spilling over the deck or into engine room.
Remote cables: tanks containing fuel and oil will have high and low suction valves with remote cables fitted, this way in the event of a fire in engine room the tanks can be isolated from a remote (safe) position.
Manholes: these are provided to give staff access to tank for cleaning and repair. To gain access manholes are unbolted after ensuring tank is empty. However its vitally important that before any person is allowed to enter the tank a strict procedure is followed (tank entry procedure) to ensure tank is safe for human occupation. An example of procedure to follow for entry into enclosed space (tank) can be found in the code of safe working for merchant seamen that is produced by the UK administration. The procedure is also clearly set out in ships safety management system (SMS).
What is the purpose of filtration?
The process of filtration of lube and fuel oils removes unwanted particles of material such as cotton threads, paint chippings and small pieces of metal. These would otherwise cause damage to pumps and machinery if left to circulate with the oil. Filtration will only separate a small amount of water from oil, however by pumping heated lube oil into a vacuum chamber, vaporisation of water can be achieved. Also, water repellent and water coalescing filter cartridges can be used, which can cause some separating of water from oil.
What are the types of filter in use?
Many different types of filters are manufactured, the simplest being the wire mesh type that are fitted in pairs in lube oil piping system. One filter is used at a time and this arrangement enables the operator to clean the filter not in use without shutting down the oil system. Others can be cleaned while in operation and maybe fitted in pairs in piping system or on its own. Wire gauze type filters are made with coarse or fine mesh depending upon the positioning of the filter unit in the oil system. An example of this are the hot and cold oil filters fitted in oil burning and pumping installations. The coarse mesh suction filters are used for cold oil and the fine mesh discharge filters are used for the heated oil. The wire mesh type filter doesn’t filter out fine particles and so if fine filtration is required other filter types are used like the auto-klean strainer.
Describe the operation of a Auto-Klean Strainer?
This filter can be cleaned while in operation. It can filter out particles down to 25 in size. The dirty oil passes between a series of thin metal discs mounted upon a square central spindle. Between the discs are thin, metal, star shaped spacing washers of slightly smaller overall diameter than the discs. Cleaning blades, fitted to a square stationary spindle and same thickness as the washers, are between each pair of discs. As the oil passes between the discs, solid matter of sizes larger than the space between the discs remain upon the periphery of the disc stack. The filter is cleaned by rotating the central spindle, which rotates the disc stack and the stationery cleaning blades scrape off the filtered solids, which then settle to the bottom of the filter unit. Periodically the flow of the oil through the filter unit is interrupted and the sludge in the bottom well is cleaned out. These are fitted in pairs so one is cleaned and other is in operation. Pressure gauges are fitted before and after the filter unit to indicate the condition of the filter. The pressure difference across the filter is low when filter is clean and it becomes progressively higher as the filter starts to become clogged up. The pressure difference shouldn’t become too high as the flow of oil then start to become restricted so flow rate reduces.
Draw a sketch that illustrates the internal arrangements of a Auto-Klean filter unit which can be arranged for automatic or manual operation.
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With the aid of a sketch describe the operation of a streamlined LO filter?
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The streamlined filter consists of a two compartment pressure vessel containing a number of cylindrical filter cartridges. Each section rod is held in longitudinal compression. The discs can be made from a wide variety of materials, for lube oil special paper discs are generally used. The oil can flow from the dirty to the clean side of the filter via the small spaces between the compressed discs then up the spaces formed by the hole in the disc and the rod. In this way, the dirt is left behind on the periphery of the dis stack and particles of the order of 1 can be filtered out, meaning this filter maintains the oil in a very good condition without the need for other treatment plants. For cleaning, compressed air is used. Closing A and B and opening D and and C results in reversal of flow.
What are filter coalescers?
These have been designed to replace the centrifugal method of particulate and water removal from fuel and lube oils. The unit consists of a pre-filter for particulate removal followed by a compressed, inorganic fibre coalescing unit in which water is collected into large globules. Coalescing action occurs which is the molecular attraction between the water droplets and the inorganic fibres is greater than that between the oil and the fibres. As the number of droplets increases they join together to form a layer of water. When the water globules are large enough they will drop to the bottom and out of the coalescing unit. Downstream of coalescing cartridges are PTFE coated, stainless steel, water repelling screen that acts as a final water stripping stage. Water gravitates from them and from the outlet of the coalescer cartridges into the well of the strainer body from were its periodically removed. The unit also makes use of pumps, motors, alarms, indicators, water probes with automatic water dumping, heaters to lower the viscosity of the oil as well as a filtration system.
What’s the purpose of oil eliminators?
Oil eliminators can be used to remove oil mist from air flows that have been contaminated with oil areas such as LO tanks or engine crankcases and car decks on ro-ro ships.
With the aid of a sketch describe the operation of a lube oil filter coalescer
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LO in circulation round a closed system, for example generators will absorb moisture from the atmosphere which will reduce the lubricating properties. LO filter coalescers are used to remove solid particles of 3 and above and also up to 99% of the water present in the oil, which can be partly due to the moisture from atmosphere.
Operation
Lube oil is pumped through the water coalescer filter cartridges, which remove solids and gather into large and coalesce (gather into larger droplets) the water droplets held in suspension in the oil. Most of the water than gravitates to the bottom of the body and the oil with remaining water droplets passes to the water repelling screens, which permit passage of oil only. Water droplets that collect on the screens eventually settle at the bottom of the body. To clean the unit, it must first be drained and then the filter cartridges are renewed, and the water repelling screens don’t need to be touched. A heater would be fitted in the supply line to heat the lube oil and assist in separation.
What are Centrifugal filters?
These are filters sometimes fitted to smaller diesel engines that utilise centrifugal force to remove some of the carbon from the oil which is then prolonging the time between overhauls. The oil is introduced into the unit under the lube oil system pressure. The oil is then directed out of small hole in the bottom of a rotating drum. Inside the cylinder part of the drum a card is placed and as the bulk of the oil is introduced into the body of the unit the heavy material accumulates on the card. After a period of time the card is changed to take out the accumulated carbon.
What are some precaution to be taken when bunkering and transferring fuel?
All scuppers to be plugged so that in the event of a small spillage on to the deck it is contained and can be dealt with
Drip trays must be placed under the ship to shore connection
Good communication between ship and and shore must be established and checked to regulate flow as desired
Personnel operating the system must be fully conversant with layout of pipes, tanks, valves and pumps
Moorings and hose length should at all times be such that there is no possibility of stretching or crushing the hose
Ensure blank at opposite at opposite end of cross over pipe is securely in place
Air pipes should be clear, soundings checked and depth indicators tested
When carrying out fuel transfers on ships it should be done during daylight hours. Under the merchant shipping act 1995, oil is not to be transferred ashore at night unless agreed first with harbour authorities, and the overboard discharge connection should be closed and secured, overflow alarm should be tested and sounding done at frequent intervals.
With reference to oil fuel installations
What are some good watch keeping and safety practices?
Ensure there is minimal oil escaping from any system or equipment and any oil that does escape cannot be heated to or above the flash point because this is very dangerous as it can result in explosion or fire
After lighting burners, the torches must be fully extinguished by means of appliances provided
Cleanliness is essential to safety, no oil or combustible substances should be allowed to accumulate in bilges or gutter ways or on tank tops or boiler flats
Before any oil tank that has contained oil fuel is entered into for any purpose the oil should be entirely removed, all oil vapour must also be removed by steaming and ventilation. test of the atmosphere in tanks or bunkers should be made to ensure safety before inspection or work is carried out.
Boiler, settling tank and oil fuel unit spaces must be clean, no combustible materials in the vicinity and there should be good access. Oil tanks, pumps should be fitted as far from boilers as possible and provided with trays, gutters and drain cocks.
All equipment should have self closing and sounding or indicating devices
Relief valves should be fitted to discharge to an overflow tank fitted with level alarms and filing stations should be isolated, well drained and ventilated.
Every oil tank must have at least one air pipe, is this overflow pipe and should return to an overflow tank
Oil pipe fittings should be made from steel and hydraulically tested. Oil units should be in duplicate and capable of being shut down remotely and provided with shut off isolating devices.
Valves or cocks fitted to tanks in the machinery and boiler spaces should be capable of being operated from a remote position above the bulkhead deck.
No artificial lights that are capable of igniting oil vapour
Ventilator and dampers must have reliable operating gear clearly marked with shut and open positions
Particular care is advised during bunkering to avoid overflow (gravitating is always the safer option if possible)
With reference to high viscosity fuel oil:
a) Explain how it is treated between storage tank and main engine; (10)
b) State the purpose for the treatment (6)
a.) fuel is stored in double bottom storage tanks (bunker tanks). fuel is then heated by using steam heating coils lower its viscosity and allow for easier fuel transfer.
fuel is then transferred using fuel oil transfer pumps through course filters which remove large contaminants before it enters the settling tank.
when being transferred through fuel transfer lines fuel is receiving external heating from steam tracing system to maintain temperature.
Once in the Settling tank the fuel is heated through the use of steam coils inside tank to increase the relative density between the fuel and any water or sludge present. then the sludge and water is separated by gravity. when in the settling tank water mixed with sludge can be removed from the tank by using the drain valves located at bottom of tank.
fuel oil is then transferred by the centrifuge pump through to a heater to raise its temperature to about 90 degrees celsius and then goes onto the purifiers. in the purifier contaminants and water are separated from the fuel through the use of centrifugal force. after separation fuel is discharged through the purifiers through to the daily service tanks.
From the daily service tank supply pumps take suction from the service tank and discharge fuel to the Mixing tank.
Booster pumps then take suction from the mixer tank and fuel passes through a steam heater which increases the temperature and reduce the viscosity to the required setpoint (approx. 12 Cst 120ºC). This is controlled by a ViscoTherm.
Finally fuel will pass through a set of fine filters before going on to the main engine.
b.) To remove water and prevent emulsifying the fuel.
to remove solids as well as liquid contaminants. solid contaminants being mainly rust, sand, dust and refinery catalysts and liquid contaminants being mainly fresh or salt water.
The fuel oil treatment system reduces the level of contaminants and conditions the fuel so that its ready for use meaning the fuel viscosity has been reduced for correct injection and combustion and temperature has been increased.
State the changes in the fuel preparation required when changing to a fuel of lower density and viscosity
The change over from high viscosity fuel (HFO) to low viscosity fuel (DO):
Preheat the diesel oil in the service tank to about 50 degrees Celsius.
Cut of the steam supply to the FO preheater and steam tracing
Reduce the engine load to about 75% MCR load.
Change to MDO when temperature of HFO in preheater has adjusted to about 25 degrees Celsius above the temperature of the diesel oil service tank so about 75 but must not be below.
Open the DO supply line valve and change the three-way regulating valve so that suction is taken from the DO service tank.
Then close the FO supply line so DO can then be led to the supply pumps.
The temperature of the diesel oil will continue to rise at a rate of about 2 degrees Celsius per minute until the required viscosity is reached.
During the change-over procedure the temperature of the fuel must not change more than 2°C
each minute to prevent damage to the system. The small change rate is also because of the large difference of viscosity between HFO and MDO
visco-therm controller has to be adjusted in order not to over-heat the fuel reducing viscosity too much will risk carbonisation or gassing up the fuel lines. The engine fuel injection timing must also be adjusted to compensate for less viscous fuel.
a) Describe the test that is carried out on a fuel injector after overhaul and
before it is refitted to the engine. (8)
bi) Sketch a section through the nozzle of a fuel injector. (8)
a.) * Injector shall be mounted into the test rig
- With the injector priming valve open, hand pump operated until fuel flows from the priming valve. Priming valve can then be closed.
- Hand pump should then be operated
rapidly for several strokes. The injector
should open with a high pitched noise
and fuel should be emitted in a fine cloud. Verify opening pressure of injector needle valve. Adjustment can be made to the adjustment nut to increase or decrease the opening pressure. - then test for tightness between the nozzle needle and seat, the hand pump should be operated slowly to increase the pressure just below the opening pressure. Pressure should be
maintained for a few seconds and nozzle checked for signs of dripping - To test for tightness between needle and guide, hand pump
should again be operated to increase pressure to just below
opening. Observe the pressure gauge. If pressure drops quickly nozzle needs to be replaced.
b.) SEE EOOW IAMI/ORAL Sketch Pack for drawing
a) State why the simultaneous injection of fuel oil and starting air into a main engine cylinder is undesirable.(2)
b) Explain how simultaneous injection of fuel oil and starting air is prevented.(4)
c) Explain how a leaking air start valve is detected while the engine is
running.(4)
d) Describe the actions to be taken upon discovery of a leaking air start valve.(6)
a.) Simultaneous Injection of Fuel and Starting Air into a Cylinder is Undesirable as it could lead to an Explosion in the Start Air System.
Pressure relief valves may lift, causing hot fuel oil to spray onto hot parts of the engine.
b.) It is prevented by means of Interlock, which prevents Fuel being Injected when the Air Start Auto Valve is Open.
The Interlock Operates a Stop Solenoid, which keeps the Fuel Rack at Zero Position. Starting interlocks of the air start valve in order to stop fuel supply until air is released. During manual starting, the operator will only apply fuel once the engine is up to starting speed and after the air has been closed.
c.) Hot branch pipeline with possible paint discoloration. Activation of air start line, bursting disk prevention device. During start-up of the engine or during slow turning any air leakage through the O-ring on the starting air valve can easily be detected by observing if any spray of water comes from the leaking O-ring.
d.) Inform the bridge and CE of the situation and request for the engine to be stopped. isolate fuel from affected unit and open indicator cock. Then the starting air branch on the starting air manifold will have to be blanked off to isolate air. Reversing control can then be operated, and the engine can be given a small starting air in the reverse direction to obtain a different crank position or the turning gear could be engaged and one of the pistons shall be moved in position just after top dead centre to get the positive torque to turn the engine.
a) With respect to the fuel injection timing of a 2-stroke diesel engine, what
would be the effect of:
(i) Early injection; (6)
(ii) Late injection (6)
b) Sketch an “out of phase” (draw card) for a 2-stroke diesel engine and indicate
the point of the fuel injection. (4)
a.) i.) effects:
- High peak pressure, Increased power
Less SFOC, Drop in exhaust gas temps
and High thermal efficiency - A heavy shock load will be transmitted to the running gear and bearings with a knocking sound
- Sever stress loading of piston rod, con rod, cross head bearing and bottom end bearings.
ii.) effects:
- Low peak pressure, loss of power, incomplete combustion, High exhaust temp & black smoke
- Increase in SFOC Reduced thermal efficiency uneven thermal distribution throughout piston liner, causing micro-seizure and liner cracking.
- Heavy carbon deposits on piston, and cylinder liner and fuel oil wash down due to incomplete combustion
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Draw a line diagram of a fuel oil system from fuel oil storage tanks to the daily service tank, for a large diesel engine plant using HFO. Label all the main components of the system including any safety devices fitted. (16)
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explain what is sounding and what does a sounding table contain?
In order to maintain the ship’s stability, and safety, it is required to monitor the fluid levels at regular intervals. The technique of determining the fluid level in a ship’s various tanks is known as “sounding” of the tanks. During bunkering operation to check the fluid level in tanks at regular intervals, using vessel remote sounding instrumentation or by using a sounding tape. Sounding tape is a measuring tape (in meter or inch) normally made up of brass and steel with a weighted bob attached at the end of the tape using a strap hook. at the end of bunkering operation the sounding tape value is subsequently utilized in the calculation of the final sounding value, which is determined using the sounding table, taking into account the list and trim of the ship and the temperature at which the fluid is stored as density of oil is effected by temperature.
Sounding table is a table containing capacity and most importantly the volumetric content of the tank at given depth of sounding and all vessels have their own specific sounding table documents for each tank containing fluid in bulk. The sounding table is compiled to show the volumetric quantity of fluid at various trims and list for the particular sounding depth in cm. On board ship, it is essential to maintain an accurate record of the amount of liquids (in all forms) contained in each tank. A ship is equipped with several forms of automatic and hydraulic/ pneumatic/ mechanical sounding measurement systems, allowing the liquid level to be monitored remotely or locally without the need for manually measuring and calculating the amount of liquid within the tank. However, one cannot rely solely on automation and mechanical devices and manual sounding is always favoured in order to reconfirm the fluid level in the tanks, assuring that the tanks will never overflow or run dry.
explain what specific requirements must be followed for bunkering in a US Port?
there are some specific requirements with regard to oil transfer onboard vessels and US authorities issue a set of rules that must be followed if the vessel intends to bunker in any of US ports.
The Master of the vessel must notify the port authority of the intention to bunker well in advance, stating the location, type of bunker, oil to be transferred, and the expected time of bunkering.
C/E will hold a meeting with all ship’s staff who will be involved with or responsible during bunkering on a bunkering plan at least 24 hours prior to bunkering operations, where the following will be discussed and agreed upon:
Roles and responsibilities specific to assigned task of each individual
Tanks that will be made available for bunkering
Plan on extent of filling of each tanks
Valves to be lined up for the operations
Closing of scuppers on deck
Communications between supply vessel and receiving vessel
Flow rate
Frequency of checking tank soundings
Spill response
Pre-bunkering Check list is to be filled in for compliance. All check lists are to be maintained on board at least for a minimum period of two years from date of bunkering or as per company management system instructions. Before bunkering begins, the Chief Engineer must double-check all details on the delivery papers as presented by the barge supplier’s representative to ensure that the bunkers delivered match the quantity and specifications stated in the prior Bunker Confirmation message.
Chief engineer and his / her designated engineers shall verify that the following is also complied with prior to commencement of bunkering.
1.All self closing devices on sounding pipes operate correctly and easily, and closed after use.
2.Prior to bunkering air pipes from all tanks are in order. This includes checking that the safety gauze is not blocked with paint thus reducing the air flow. Where Press/Vac valves are fitted, they shall be checked for free movement.
3.Heavy fuel oil vapours are measured for Hydrogen Sulphide (H2S), preferably on board the barge. The acceptance level of H2S in the tank atmosphere is up to 200 ppm. If H2S in the tank
atmosphere is found in excess of 200 PPM, the fuel should be rejected and the parties in barge of vessel’s bunker supply notified accordingly. About H2S will discuss on a later post.
what is the sulphur content in ECA zones and outside ECA zones?
ships now trading in ECA areas must use fuel with no more than 0.01 % sulphur content and the maximum sulphur limit outside ECA’s is 0.5 % unless the vessel is fitted with an approved Exhaust Gas Cleaning System, therefore checking the quality of bunkered fuel has become even more crucial, due to the fact that Port State Control inspectors may check fuel inventory records to ensure the ship utilized the correct fuel within an ECA or an EU Community port and complied with other national sulphur standards. Most ships have bunkering check-lists and procedures in place to mitigate fuel spills and follow shipping regulations.
ECAs are sea areas that limit SOx and NOx emissions
ECAs are designated in the following locations:
Baltic Sea area.
North Sea area.
United States Caribbean Sea area (near Puerto Rico and the United States Virgin Islands)
North American area (covering designated Pacific and Atlantic coastal areas of the United States and Canada, including Hawaii)
what must be done prior to bunkering?
Prior bunkering operation, the Chief Engineer should create a bunkering plan that specifies which tanks would be used for bunkering and to achieve an efficient and safe operation, all staff must be fully aware of this before the operation begins. There should also be enough known-quality fuel on hand to use until the newly bunkered fuel is tested by a certified laboratory.
As part of pre-bunkering preparation you must check the following:
All tank lids are closed and locked, and that all bunker tank air vents are open and clear.
Overflow tanks must be empty
All level gauges, high-level alarms, and remote-controlled valves on bunker tanks must be operational.
Check that manual sounding tapes are available and that the soundings pipes are not clogged or obstructed.
Check that all valves to the receiving bunker tanks are properly aligned and that all other valves are closed.
Check the filters and safety valves on the bunker lines, if installed.
All bunker lines and transfer hoses should be pressure tested, and safe operating pressures should not be exceeded.
Check that the bunkering hose is properly and securely connected to the ship manifold.
Check ahead of time that you have the proper equipment to take a sample before bunkering: a continuous drip feed sampler (which must be a MARPOL Annex VI compliant line sampling device)
fully explain the bunkering operation?
During bunkering operations, the hose connection must remain intact and leak-free, and this must be checked regularly during the operation, especially when the barge switches tanks and pressure is dropped for a brief period of time. If the fuel is not homogeneous, the bunker line pressure may also fluctuate. To sample properly, we must employ adequate equipment to collect representative samples that are acceptable to all parties involved. The dependability of test results from fuel quality analysis and the fuel density used in quantity measurement calculations is based on proper sample methods being followed. The sampling device is installed at the point of Custody Transfer, which is typically at the ship bunker manifold, which is the preferred location for joint sampling in agreement with the fuel supplier (this is very important in case to any future quality disputes). The Chief Engineer must examine the quality of the fuel given by the bunker barge supplier when the barge first arrives. They accomplish this by validating the quality and quantity of fuel mentioned on the Bunker Delivery Note (B.D.N).“Details of fuel oil for combustion purposes delivered to and utilized on board shall be recorded by means of a Bunker Delivery Note,” according to MARPOL standards. As a result, a BDN should be presented for each delivery and fuel grade delivered, and it should be stored on board and easily accessible for inspection at all times. The ship and the provider are both required to keep it for three years after the fuel oil has been delivered.
The BDN must include information such as the receiving ship’s name and IMO number, the bunkering port, the date the bunkering began, the name, address, and phone number of the marine fuel oil supplier, the product name and grade, the quantity in metric tones, the density at 150C in kg/m3, and the sulphur content in percentage by mass. The IMO further suggests to include the seal number of the MARPOL Annex VI fuel sample on the BDN for cross-referencing reasons, as well as a declaration signed and validated by the supplier’s representative declaring that the fuel complies with MARPOL Annex VI.
The BDN may be prepared prior to delivery in some situations, but this will not reflect the realities of the delivery.
It is very important to note that you should NEVER sign the BDN, sample labels, or any other document until the bunkering operation is complete.
The Chief Engineer will decide which tanks will receive the fuel before the barge arrives, and the contents of each receiving tank should then be measured and documented. These should ideally be empty, as different types of fuel may not be compatible. Blending fuels should be avoided unless absolutely necessary, as it can cause operational issues. Because some vessels lack a remote level measuring technology, you may need to use a sounding tape.
Bunker
Check that the barge’s documentation show the correct grade and quantity of fuel, and agree on sample protocols when it arrives. Careful measurements of the barge tank contents must be taken before connecting the bunker hose. Use your own sounding tape or ensure that the equipment on-board the barge is in good working order and has not been tampered with. Some barges will feature calibration tables for ullages and others for tank content soundings. Check that the right reference point on deck is being utilized for taking ullages as this information should be available in the barge calibration tables. Always accompany the Barge Master while taking ullages or soundings of any barge tanks. It is critical that all of the tanks on board barge are dipped and their levels recorded and this includes tanks that have been reported empty as well as those that may contain fuel for another vessel.
After taking each measurement, make a note of it and double-check that the barge operator agrees with your reading as these are critical measurements in determining the amount discharged by the barge, and both parties should sign the opening measurement records. Temperature readings of each tank are also critical, because the volume of bunkers rises with temperature. Temperature changes can create considerable mistakes in calculations, hence thermometers should be checked on a regular basis. Typically, the terms and conditions of the sale indicate that the quantity of fuel delivered will be determined by shore meters or barge outturn measurement. The Chief Engineer or a representative from the ship should be present at the bunkering barge to observe the opening and closing meter readings, barge soundings, and temperature readings. Fuel sampling should be carried out by continuous drip method for the entire duration of the bunkering process. The sample is first collected in a cubitainer which is screwed onto the drip sampler and secured with a seal in order to prevent any unauthorized changes in the adjustment of the drip rate during sampling. Barge Master and the Chief Engineer should be invited to witness the adjusted drip-rate and sealing process and security seal number should be recorded.
To ensure that the sample represents all of the fuel bunkered, the sample needle valve should be adjusted to collect enough of each fuel type for all of the required fuel samples without overfilling the cubitainer, which needs to be able to hold enough oil for all of the samples that you may need:
a MARPOL sample
a retained sample for the ship to keep
a retained sample for the barge to keep
a retained sample for the testing laboratory
if the vessel is utilizing a bunker surveyor, an extra sample may be required.
The ship should also be given a retained sample from the bunker supplier, which should be taken properly on the bunker barge. If the sample cannot be obtained from the ship manifold for any reason (vacuum in the line, extreme weather, etc.), the cause should be recorded in the ship’s log book and the sample taken elsewhere. Throughout the bunkering operation, specific crew members should be appointed to ensure that there is always one vessel representative overseeing the activity (monitoring the bunker manifold and the sampling equipment, continuously checking for leakages etc.). Record any start and stop times as well. All of the above responsibilities can be overseen by an experienced and certified bunker quantity surveyor, who can assist the Chief Engineer in ensuring proper bunkering and sampling procedures are followed. When the delivery is complete, the vessel representative should witness the closing soundings on the barge in order to determine and validate the actual volume provided.
To accurately calculate how much fuel has been received the following steps should apply:
check the volume received and the observed temperature of the fuel.
take soundings or ullages of all tanks that have received fuel and correct the soundings or ullage according with the vessel’s trim and list.
after correction the observed volume you have received can then be calculated.
It should be noted that vessel calibration tables for fuel storage tanks are rarely approved by recognized bodies, but bunker barge calibration tables are routinely reviewed and certified by local authorities.
after determining the observed volume, you must correct it to the standard of 150C.
to determine the correct Volume Correction Factor (VCF), you must first check the density of the fuel at 150C, which will be provided by the supplier.
the observed volume is then multiplied by the temperature correction factor contained in tables such asASTM 54Bto determine the standard volume at 150C.
because density in a vacuum is an absolute relationship between mass and volume, it will not be the same as weight to volume in air. To calculate the right density in air, multiply the supplied density by a Weight Correction Factor, which may be found inASTM 56table.
after that, we can multiply the standard volume at 150C by the corrected density to determine the number of tons of fuel received.
Many fuel testing laboratories discover that the density on the BDN is frequently exaggerated, implying that the supplied weight was less than it seemed.
If the density cannot be found from a representative sample, the BDN should only be signed for volume at the observed temperature, but if the supplier insists on a signature for weight, add“For volume only – weight to be determined after density testing of a representative sample”to the Remarks section in the BDN. When the delivery is finished, the surveyor should concur with the Chief Engineer and Cargo Officer that the bunker delivery is completed. When the bunkering is finished and the cubitainer is full of fuel, close it and shake it for a few minutes to completely mix the sample. Because we will frequently be preparing at least four samples, fill all of the sample bottles one-third at a time, making repeated passes to fill each bottle evenly. Close and seal the sampling bottles, and record the seal numbers on the Sample Details Form. Sign the labels on the fuel quality testing samples with the supplier representative. and put a label on each bottle with both signatures. Under no circumstances should you sign any blank labels or accept any samples that have been created or supplied in advance of the bunkering process. It is critical that you keep one sample on board in a secure area since this may be the only sample remaining that accurately represents the fuel delivered to the ship.
If the supplier provides a sample but it was not witnessed, apply the mark “Only for receipt. Unknown source” on its label. The fuel supplier is required to give you a representative MARPOL sample, which must be sealed and signed by a representative of the company. This MARPOL sample must be kept under the ship’s control until the fuel oil is considerably depleted but not for less then twelve months after delivery.
what is residual fuel?
By definition, residual fuel oils are the by-products of refinery processes that remain after the distillate or lighter fractions have been removed. These residues are complex mixtures that vary depending on the source of the crude oils processed and the refinery’s complexity.
what is an oil refinery?
An oil refinery can be thought of as a factory that transforms crude oil into a variety of useful products. It is designed to meet market demands in the most cost-effective and efficient manner possible. The first step in the manufacture of petroleum products is the atmospheric distillation of crude oil into its major fractions. When crude oil is heated, the lightest, most volatile hydrocarbons evaporate first, followed by the heaviest, least volatile hydrocarbons. After cooling, the vapors are condensed back into liquids. A fractionating column is used to carry out this distillation process. The column is divided into chambers by perforated trays that condense the vapours and allow the liquids to flow into storage tanks at each stage. The crude oil is preheated to a maximum of 350°C to avoid thermal cracking.
why is it important to pressure test bunker lines?
how do you pressure test bunker lines, what is the test procedure and what must be taken in to consideration when carrying out such a test?
purpose of this periodical test is to find if something is wrong with the fuel oil bunkering system and to take all necessary actions to re-mediate the faults and defects within. Chief Engineer is responsible for performing the pressure test of the bunker line on an annual basis when each transfer pipe on-board a vessel must be tested under static liquid pressure, at least 1.5 times the maximum allowable working pressure (MAWP). Special attention should be paid to flange joints, valve gland packing, pump seals etc. The test preformed to pressure test the vessels bunker lines is a hydrostatic test.Hydrostatic test is a test conducted by filling a space with a liquid to a specified head. Unless another liquid is approved, the hydrostatic test consists of filling a space with either fresh or sea-water, whichever is appropriate for the space being tested. This kind of test is usually performed during vessel’s periodical special survey (dry docking) using fresh water, but sometimes needs to be done also on-board. MAWP is considered to be the design relief valve pressure setting of the relief valve on the bunker transfer pump. In the absence of the relief valve the MAWP should be taken to be 5.0 kg/cm2.
In order to perform the test on-board the following should be taken into consideration:
A “Permit to Work” should be issued and a “Risk Assessment” must be carried out.
Before conducting the test, all scuppers should be sealed and adequate oil spill equipment should kept ready on deck.
The test should be performed for a period of 10 minutes under a constant hydrostatic load.
The pressure rating for pipe line material should not be exceeded. This pressure can be found and verified into the vessel’s bunker plan and/or piping diagram.
During testing onboard bunker transfer pump may be employed for the test. If the transfer pump is a positive-displacement type, it may be stopped when the required test pressure is reached as it should not permit backflow, therefore valves before and after pump should be closed after desired pressure has been reached. If a centrifugal pump is used for testing, constant running is required to ensure the necessary pressure is maintained.
The test should be conducted while underway at sea at least 200 nm from shore during day light.
Similar test procedure applies for fuel oil and lube oil bunker lines.
After the test, the date and test pressure should be stenciled on the pipe lines and deck at prominent locations.
The stencil should be: ”Hydro Test Date: xx/xx/xxxx Pressure: xx kg/cm2.
The actual testing procedure should comprises of the following steps:
Minimum pressure test must be 4 kg/cm2.
The bunker line relief valve if fitted must be removed and a blank with a drain valve must be fitted. As an alternative, the relief valve set pressure can be increased and test the bunker line pressure to a value at least 1.5 times, the normal operating set pressure of the relief valve. In the absence of the relief valve the MAWP should be taken to be 5.0 kg/cm2.
At the bunker station, fit a flange, fitted with pressure gauge and a connection for a suitable hand pump. The connection should be fitted with a gauge/cock for pressure monitoring. You must ensure that the gauge is verified and calibrated.
A communication between engine room and deck must be established and personnel must be arranged to monitor for any leaks on deck and engine room.
Use the transfer pump to fill bunker lines up to the manifold. Purge the lines via valves/cocks on manifold.
After the line is filled with oil, the pump valves and system valves must be closed. A hydraulic hand pump can be connected to the manifold to build up the pressure or same can be done with the transfer pump but caution must be taken in order not to damage the pump.
Maintain the pressure for 10 minutes and check the entire system for leaks.
After completion of test drain the pressure into the overflow tank through the relief valve connection or by slowly opening the valve to an empty bunker tank.
It is very important to remember that you’re not allowed to test the system by air and by doing so it will makes the test worthless and void.
The Coast Guard recognizes that achieving the test pressure of 1.5 times MAWP for annual bunkering test on vessels is often impractical while vessel are in service or outside shipyards where special equipment may not be available. Therefore, the Coast Guard will accept the following:
The vessel operator submits a written request for the alternative at least 30 days before operations under the alternative proposed, unless the Captain of the Port authorizes a shorter time.
The alternative provides an equivalent level of safety and protection from pollution by oil or hazardous material, which is documented in the request.
what is SOx, CO2, NOx, PM?
Sulphur oxide (SOx). Most ships use heavy fuel oil (HFO). This has relatively high sulphur content compared with other types of fuel. This sulphur is released into the atmosphere through the ships exhaust gas system in the form of sulphur dioxide, which leads to acid rain and is harmful to the environment. Carbon dioxide (CO2). Nitrogen oxide (NOx) just as the SOx is also harmful to the environment and can be caused by improper combustion or high cylinder pressure and temperatures. Particulate matter (PM), are particulates found in the air which include dust, dirt, soot and smoke.
what are chemical compounds?
Substances which are made up of more than one type of element and are chemically bonded together
what is Dew Point?
The temperature below which the water vapour in a volume of air at a constant pressure will condense into liquid water.
what is limestone and caustic soda
alkali chemical compound that neutralise acids
purpose of fuel oil system?
The fuel oil system for a diesel engine can be considered in two parts—the fuel supply and the fuel injection systems. Fuel supply deals with the provision of fuel oil suitable for use by the injection system. the purpose of the whole fuel oil system is to introduce fuel oil into the engine cylinders at the correct time, at correct pressure, at correct quantity and in correctly atomised form
with the aid of a system sketch explain the fuel oil supply system
In the system shown in Figure 2.11, the oil is stored in tanks in the double bottom from which it is pumped to a settling tank and heated. After passing through centrifuges the cleaned, heated oil is pumped to a daily service tank. From the daily service tank the oil flows through a three-way valve to a mixing tank. A flow meter is fitted into the system to indicate fuel consumption. Booster pumps are used to pump the oil through heaters and a viscosity regulator to the engine-driven fuel pumps. The fuel pumps will discharge high-pressure fuel to their respective injectors. The viscosity regulator controls the fuel oil temperature in order to provide the correct viscosity for combustion. A pressure regulating valve ensures a constant-pressure supply to the engine-driven pumps, and a pre-warming bypass is used to heat up the fuel before starting the engine. A diesel oil daily service tank may be installed and is connected to the system via a three-way valve. The engine can be started up and manoeuvred on diesel oil or even a blend of diesel and heavy fuel oil. The mixing tank is used to collect recirculated oil and also acts as a buffer or reserve tank as it will supply fuel when the daily service tank is empty. The system includes various safety devices such as low-level alarms and remotely operated tank outlet valves which can be closed in the event of a fire.
what’s the function of a fuel injection system
The function of the fuel injection system is to provide the right amount of fuel at the right moment and in a suitable condition for the combustion process. There must therefore be some form of measured fuel supply, a means of timing the delivery and the atomisation of the fuel. The injection of the fuel is achieved by the location of cams on a camshaft. This camshaft rotates at engine speed for a two-stroke engine and at half engine speed for a four-stroke. There are two basic systems in use, each of which employs a combination of mechanical and hydraulic operations. The most common system is the jerk pump; the other is the common rail.
describe the jerk pump fuel injection system
In the jerk pump system of fuel injection a separate injector pump exists for each cylinder. The injector pump is usually operated once every cycle by a cam on the camshaft. The barrel and plunger of the injector pump are dimensioned to suit the engine fuel requirements. Ports in the barrel and slots in the plunger or adjustable spill valves serve to regulate the fuel delivery (a more detailed explanation follows). Each injector pump supplies the injector or injectors for one cylinder. The needle valve in the injector will lift at a pre-set pressure which ensures that the fuel will atomise once it enters the cylinder. There are two particular types of fuel pump in use, the valve controlled discharge type and the helix or helical edge pump. Valve-controlled pumps are used on slow-speed two-stroke engines and the helix type for all medium- and high-speed four-stroke engines.
describe the operation of a helix type injector pump
The injector pump is operated by a cam which drives the plunger up and down. The timing of the injection can be altered by raising or lowering the pump plunger in relation to the cam. The pump has a constant stroke and the amount of fuel delivered is regulated by rotating the pump plunger which has a specially arranged helical groove cut into it. The fuel is supplied to the pump through ports or openings at B (Figure 2.12). As the plunger moves down, fuel enters the cylinder. As the plunger moves up, the ports at B are closed and the fuel is pressurised and delivered to the injector nozzle at very high pressure. When the edge of the helix at C uncovers the spill port D pressure is lost and fuel delivery to the injector stops. A non-return valve on the delivery side of the pump closes to stop fuel oil returning from the injector. Fuel will again be drawn in on the plunger down stroke and the process will be repeated. The plunger may be rotated in the cylinder by a rack and pinion arrangement on a sleeve which is keyed to the plunger. This will move the edge C up or down to reduce or increase the amount of fuel pumped into the cylinder. The rack is connected to the throttle control or governor of the engine. This type of pump, with minor variations, is used on many four-stroke diesel engines.
