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ANAND VARDHAN TIWARY

About Me

1976-08-25
I am chief engineer and also part time administrator of Sailors Club
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Kolkata
India
Member since
Saturday, 17 December 2011 11:17
Last online
7 hours 20 minutes ago
  • ANAND VARDHAN TIWARY shared a photo in the Anand Tiwary's Photos album
    Engine room's "not so" Minions.
    2 hours 27 minutes ago
    ANAND VARDHAN TIWARY Engine room's "not so" Minions.
    2 hours 27 minutes ago
  • The hijackers say they want to use the Indian crew to secure the release of pirates jailed in India.
    2 weeks ago
  • The boat was filled with guests returning from a wedding.
    2 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Refrigeration System' in the forum.
    (A) Drop in suction pressure will lead to excessive carryover of crankcase oil or there could be leakage from the crankcase shaft seal.

    (C) Causes of the excess icing in the Compressor suction are following:
    1. Over charging of refrigerant.
    2. Faulty Thermostatic expansion valve.
    3. Blocked evaporator due to icing or under-size evaporator.
    4. Faulty back-pressure valves of the Evaporators.

    (D) Short cycling occurs in the compressor when a mechanical failure is causing the run times to terminate prematurely and since set point has not been achieved, it restarts shortly afterward, thus requiring more compressor ‘ON’ time to compensate. Short cycling is a symptom of a potentially wide range of causes.

    Dirty condenser/automatic high pressure reset: A dirty condenser can severely limit your system’s ability to reject heat for regulating temperatures and pressures needed for cooling which can lead to compressor tripping on high head pressure. If the condenser has automatic high pressure reset it can result in short run cycles.

    Pressure or temperature control differential is too small: When the pressure controller’s low pressure differential is set too tight, it can cause the compressor to short cycle. This can be observed during normal cooling when the low pressure setting is reached and the compressor cycles off until the pressure in the evaporator rises above the high side of the low pressure setting. This results in longer times to achieve set point and greater energy use.

    Lack of operation time delay: While it’s certainly important to have a minimum and maximum run time in place for proper system performance, it’s equally important to have a minimum OFF time in the form of an operation time delay. This is arguably the most common cause of a short cycle. By having an effective time delay, you can potentially prevent other causes from infiltrating your system. For example, a proper time delay can keep the system from running due to discharged air still circulating in the system immediately after its operation. Another: it can allow the pressure controller to reset itself naturally while not calling for cooling as opposed to firing another cycle based on high pressure triggers due to compromised condensers.
    Read More...
    3 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'HEAT EXCHANGERS' in the forum.
    (a) Why turbulent flow:
    A common situation encountered by an engineer is heat transfer to fluid flowing through a tube.

    This can occur in heat exchangers, boilers, condensers, evaporators, and a host of other process equipment.

    The study of heat transfer can be done either in laminar flow or in turbulent flow. Both conditions show different performance characteristics of the heat transfer.

    Under turbulent flow conditions, the increase in heat transfer rate is more significant than that under laminar flow conditions.

    This is due to the increase in the Reynolds number of the flowing fluid in turbulent flow.

    Laminar flow develops an insulating blanket around the channel wall and restricts heat transfer. Conversely, turbulent flow, due to the agitation factor, develops no insulating blanket and heat is transferred very rapidly.

    How the turbulent flow is achieved

    1.Higher the velocity more the turbulent the flow will be.
    2.The jumbled, tumbled flow pattern can disrupt much of the stationary fluid film. Built-in obstructions to flow, called turbulators, disrupt laminar flow, thereby improving heat transfer. Although these obstructions to flow increase pressure drop through the heat exchanger, the improvement in heat transfer more than compensates for the higher pressure drop.

    (b) Impressed current corrosion protection system (ICCP) is used if there is no sacrificial anode fitted.

    Impressed current cathodic protection works by delivering controlled amounts of DC current to the surfaces submerged in water with the aid of ultra-reliable zinc electrodes as well as combined anodes of metal oxide. The electrical current that is continuously regulated and monitored by the ICCP system helps prevent the electrochemical mechanism of galvanic corrosion prior to its attack.

    (c)
    A heat exchanger is a device for transferring thermal energy from one medium to another. It generally consists of two channels or system of channels, one for each medium, and separated from each other by partitions through which heat is transferred from the hot medium to the cold medium.

    Most coolers used on board ship transfer heat from a hot fluid to sea water. For the main propulsion engine of the motor ship, the engine jacket water, lubricating oil and charge air must be cooled and generally also water or oil used in cooling the pistons.

    Straight-tube_heat_exchanger_2-pass.PNG

    The flow path of the fluids are fixed by the division plates in the heat exchanger heads for the cooling fluid and the internal baffles or tube support shets within the body of the heat exchanger for warm fluid:
    The division plates in the heads or boxes fix the position of the inlet and outlet branches for the fluid passing through the tubes.

    The internal baffles fix the position of the inlet and outlet branches for the fluid passing through the body of the heat exchanger on the outside of the tubes.

    If the heat exchanger heads do not contain any division plates, he fluid passing through the tubes enters at one end of the heat exchanger and leaves at the other. This arrangement is referred to as a single pass heat exchanger. If the heat exchanger is a double pass type, a division plate is fitted in one head. The inlet and outlet connections for the fluid passing through the tubes are fitted on this head. The division plate prevents the fluid bypassing and causes it to pass through half the tubes in the heat exchanger which is referred to as the inlet bank. After the fluid passes through the inlet bank it enters the other head which is just a bobbin piece and a cover. The direction of fluid flow is reversed in this head or box and it passes back through the outlet bank of tubes and leaves at the outlet branch. The fluid has passed through the tubes in two different paths from which it gets the name two pass, or double pass.

    In recent designs, the guided flow concept has been introduced, i.e. a secondary cooling surface in the form of radial fins integral with the tubes between which flow is guided radially, alternately out and in from section to section. This gives better heat transfer surface and better heat transfer, lower metal surface temperature and increase performance.

    (d)
    In a multipass shell and tube heat exchanger, the problem of differential expansion between the shell and tube passes is taken care of by using a U-bend or floating head tube sheet.
    adc8265112f90283a4451278.jpg
    Read More...
    3 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Boiler Feed Water' in the forum.
    (a) wpe9232052_06.png

    (b) When we measure pH, we’re measuring the power of Hydrogen. The number refers to the relative concentration of hydrogen (acid) and hydroxide (base) ions in solution.

    It comes into play with steam boilers because a pH between 7 and 9 (slightly alkaline) is just right.

    If the pH is lower than that, the water will start eating the pipes. If it’s higher than that, the water won’t corrode metal, but it may begin to foam, and that’s not good.

    Say, you’re on a job and you have a steam boiler that’s taking on a lot of feed water because the system has leaks.

    Here’s the real problem for that: Fresh feed water brings with it carbonates and bicarbonates, which are both natural and normal. The challenge starts when the water boils because carbonates and bicarbonates break down and leave the boiler as carbon dioxide. This gas flows through the system with the steam, and if you’re not venting the system well, the condensate will absorb the carbon dioxide as the steam gives up its latent heat to the pipes and the radiators. We call that Henry’s Law.

    The system winds up with carbonic acid in the returns and that’s bad news because carbonic acid removes the thin film of rust that naturally forms on the insides of steel pipes. That mild rusting is a good thing to have because it helps protect the underlying metal from further corrosion. By stripping away the surface rust, the acid makes more fresh metal available for munching. Before long, you have leaks.

    This is why it’s good to insulate the return lines in any steam system. The cooler the water gets, the more it will absorb gases such as carbon dioxide (Henry’s Law). Keep the condensate as hot as possible; it will be less acidic and the return lines will last longer. The boiler system will also use less fuel.

    And even if you fix the leaks in the system, you still have to keep an eye on the pH of the water because many people add chemicals to their boilers to avoid corrosion. These chemicals shove the pH toward the alkaline side of the scale. When the pH reaches 10, corrosion becomes impossible. That’s what makes chemical drain cleaners safe for pipes. That nasty stuff has a very high pH (think lye).

    The trouble really starts when someone gets overenthusiastic with the chemicals and the pH reaches 11. At that point, the water will foam, and that leads to wet steam, which wastes fuel because it robs the steam of its latent heat. The steam boiler has to run his burner longer to heat the building, and with lousy results.
    Use litmus paper to check the pH whenever you blow down a low-water cutoff. It’s a simple test and easy to do, and by getting the water’s pH just right, you can solve a lot of problems that are costing money.

    And please keep in mind that all steam systems are open to the atmosphere (through the Hotwell), so there’s always going to be some evaporation and a need for feed water. But steam boilers that do only space heating reuse nearly all of the water because the condensate returns to the boiler from the piping and radiators. You shouldn’t have to add too much water to these systems unless they’re leaking.

    Feed water is cold and contains lots of oxygen. People who maintain boilers deal with that oxygen by passing the feed water through a deaerator, but you’ll rarely see a deaerator on a space-heating boiler.

    Henry’s Law tells us that gases dissolve in liquids in direct proportion to pressure and temperature. So the colder the water, the more oxygen it will contain. That oxygen comes out of solution as the water boils, and it can eat holes in the boiler, right at the boiler’s waterline.

    Feed water also contains suspended solids. The more feed water you allow in, the more solids you’re going to get. The solids collect on the surface of the water as it boils. They surround the steam bubbles as they form, making them tougher. Tough bubbles resist breaking, and that also leads to foaming and wet steam. The finer the suspended particles are, the more they will collect in the bubbles, and the worse the foaming will be. You probably can’t see these solids but they’re there, and this is why you must keep the feed water to a minimum. Fix those leaks.

    (c)
    Electrochemical corrosion is practically the simplest and the most common corrosion process that is observed. Generally seen in metals.

    You can define it as a process of individual metal forming its salt byproducts.

    For this few things are needed. An agent (which is most commonly water) and a depolariser. This dipolariser can be anything from oxigens to a free anion available in acids to a another positive ( in comparison ) metal. Nitrogen is almost and inert gas.

    The basic equation is simple.

    M (metal) - M+ + e.

    This free electron is released from the outermost atom and goes to join the electron deficient depolariser. Forming salts/ oxides etc.
    Read More...
    3 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Principle of Centrifugal Separation' in the forum.
    (a) The cooling water temperature of an engine is to be kept within a certain range for following reasons:
    1. To maintain the efficient combustion, the cylinder's temperature has to be kept above 80 deg. Celsius.Excessive low temperature of cooling water will lead to heat loss and thus lower the thermal efficiency.
    2. To avoid thermal shock due to heat of combustion, the cylinder is to be kept above the certain temperature.
    3. To prevent cold corrosion of the combustion space it is required to be kept above 75 deg. Celsius.
    4. To avoid the excessive heating and thus undue expansion of the engine parts (which will lead to leakages) the cooling water temperature is kept below the 90 deg. celsius.

    (b) The principle of the working of the centrifuge is the principle of gravity which separates the water from oil. If this gravitational force can be increased the rate of separation will also increase. The centrifugal force created by the high rotational speed of the centrifuge creates separation force of about 1000 times to the gravity and thus accelerates the separation of water from the oil.

    Below is the sketch to describe the principle:

    62afeb2d3c73b6e6acd897e6.jpg
    Read More...
    3 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Gear Pump' in the forum.
    (a)

    Ext_Gear_Pump1_new.PNG

    (b) operating principle: As shown in image above there are two meshing gear inside the casing. One gear is driven from external power, while the other is driven by that gear. As the external rotary motion is applied both the gears rotate opposite to each other's direction and the from the casing side, the gear teeths carry oil as they rotate.
    Read More...
    4 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Boiler Related Questions' in the forum.
    (A) Four safety devices fitted in the Boiler and their working:

    1. Water low-low alarm: This is independent to the water level controlling system in a boiler and it activates a separate electrical relay which activates the main relay for deactivating the contactor of the Burner. Thus this device directly shuts down boiler burner on being activated.

    2. High steam pressure cut-off: This device has pressure setting higher than the auto-operation's high limit pressure setting and lower than the safety valves' pressure setting. It stops the Burner with the same type of circuitry as described in point 1 above.

    3. Burner door interlock : This device senses if burner door has opened, which could fire up the whole machinery spaces. It shuts down burner immediately.

    4. Boiler's Safety valve: This is the ultimate pressure relieving mechanical device. It is kept shut by a set spring pressure and opens at a particular pressure, while it sits back at a much lower pressure(then the lifting pressure). It thus make the steam pressure at a safe range before stopping its function.

    (B) Simple sketch of a water level gauge


    c09b098b26953b8c9cc0a42e.jpg

    (C) Boiler troubleshooting:

    1. The cause could be due to:
    a) lock out will happen, if oil temperature/pressure is not within limit values.
    b) Damper motor fault
    c) Pilot valve/ignition terminal energized
    d) Main oil valve terminal energized
    e) Internal system fault
    f) Faulty gas pressure sensor

    The engineer needs to look into above points and restore the fault.

    2. This will happen due to following:

    a) the air gap of igniter probes is incorrect.
    b) The ignition transformer is at fault.
    c) Time sequence control has a fault.

    3. This will happen due to following:
    a) If pilot oil comes for ignition then no pressure in pilot oil supply(check its line filer first)
    b) The arc which is developing is too far from the "oil cone" to catch fire (adjust ignitor orientation)
    c) Fuel is not getting atomised properly ( check oil line filters, clean nozzle or atomising cup.
    d) Water in the fuel( check for it and drain water from the service tank, purge out full fuel line to boiler.

    4. Only one cause at this stage:
    The flame eye(sensor) is dirty or malfunctioning.(Clean the flame eye, which is fitted in the burner and check its electrical circuit)
    Read More...
    4 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Relief Valve' in the forum.
    (a) The Oily Mist Detector is the equipment used to give warning of the presence of conditions that could lead to an explosion in the crankcase of a diesel engine.

    (b) Explosion door is used to relieve excess pressure that might develop as a result of a crankcase explosion of a diesel engine, is explained below:

    As a practical safeguard against explosions which occur in a crankcase, explosion relief valves or doors are fitted. These valves serve to relieve excessive crankcase pressures and stop flames being emitted from the crankcase. They must also be self closing to stop the return of atmospheric air to the crankcase.

    Various designs and arrangements of these valves exist where, on large slow-speed diesels, two door type valves may be fitted to each crankcase or, on a medium-speed diesel, one valve may be used. One design of explosion relief valve is shown in Figure. A light spring holds the valve closed against its seat and a seal ring completes the joint.

    A deflector is fitted on the outside of the engine to safeguard personnel from the outflowing gases, and inside the engine, over the valve opening, an oil wetted gauze acts as a flame trap to stop any flames leaving the crankcase. After operation the valve will close automatically under the action of the spring.
    explosion-relief-valve.jpg
    Read More...
    4 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'ME , CPP and Fuel pump' in the forum.
    (a) In case of Main engine in either FPP(fixed pitch propellor) or CPP, not responding to the Bridge control, the control needs to be transferred in Engine control room or at Emergency control.

    When transferring to ECR, the governor is still in command of ME. This is achieved by just switching the Engine control toggle to ECR CONTROL from BRIDGE CONTROL. Rest engine starting and speed control with Engine control lever in ECR in response to the ENGINE ORDER TELEGRAPH.

    However, when transferred to Emergency station control, in addition to TOGGLE CHANGE OVER to the Emergency station, the fuel lever is disengaged from the Governor control to the Hand lever control.

    The details of changeover will vary from Engine model to engine model, but for the sake of explanation, following is the procedure for the MAN B&W MC Engines:

    Procedure for Local or Emergency Manoeuvring

    The changeover and operating procedure differs from engine to engine as different control systems are adopted for different engine types; however the basic remains the same. When there is automation or remote control failure alarm then changeover of control is to be done from remote (either wheelhouse or ECR) to Local control stand.

    The local control stand is normally located in the engine room near the fuel pump platform of the main marine engine.

    Changeover Procedure

    The change over procedure can be done with marine engine in stopped as well as running condition, but if the situation permits it is better to be done when the engine is stopped.

    First change control from wheel house to ECR and both the telegraph on wheel house and ECR are to be in stopped position.

    Bring the fuel lever of wheel house and ECR in stop position.

    A changeover switch is provided in the ECR. Operate the switch from –“ECR to Local”.

    Go to the local control station and changeover the fuel pump control shaft from local to manual.

    A cone clutch arrangement or a mechanical lever arrangement may be provided, depending upon the engine type, which acts as manual control when attached to hand wheel for operating fuel rack.

    A locking pin or clip may be provided for the above arrangement as an additional safety so that it should not come out in normal operation.

    (b) The fuel control lever which is attached to the Governor is disengaged from it and is engaged to the Hand lever in the Emergency maneuvering station and is then actuated by the position of the Hand lever, which is controlled by the EOOW.

    Below is the snapshot of the manual of the MAN B&W showing the procedure of Changeover to emergency control
    a54ab08226f9fd724f4f0a3d.png
    Read More...
    4 weeks ago
  • ANAND VARDHAN TIWARY replied to the topic 'Main Engine Exhaust Gas Turbocharger' in the forum.
    (a) Construction of turbocharger:-

    turbocharger%20simple%20sketch.gif

    1.)The turbocharger consists of a single stage impulse turbine connected to a centrifugal impeller via a shaft.

    2.)The turbine is driven by the engine exhaust gas, which enters via the gas inlet casing. The gas expands through a nozzle ring where the pressure energy of the gas is converted to kinetic energy. This high velocity gas is directed onto the turbine blades where it drives the turbine wheel, and thus the compressor at high speeds (10 -15000 rpm). The exhaust gas then passes through the outlet casing to the exhaust uptakes.

    3.) On the air side air is drawn in through filters, and enters the compressor wheel axially where it is accelerated to high velocity. The air exits the impeller radially and passes through a diffuser, where some of the kinetic energy gets converted to pressure energy. The air passes to the volute casing where a further energy conversion takes place. The air is cooled before passing to the engine inlet manifold or scavenge air receiver.

    nozzle_ring.jpg

    4.) The nozzle ring is where the energy in the exhaust gas is converted into kinetic energy. It is fabricated from a creep resistant chromium nickel alloy, heat resisting moly-chrome nickel steel or a nimonic alloy which will withstand the high temperatures and be resistant to corrosion.

    5.) Turbine blades are usually a nickel chrome alloy or a nimonic material (a nickel alloy containing chrome, titanium, aluminium, molybdenum and tungsten) which has good resistance to creep, fatigue and corrosion. Manufactured using the investment casting process. Blade roots are of fir tree shape which give positive fixing and minimum stress concentration at the conjunction of root and blade. The root is usually a slack fit to allow for differential expansion of the rotor and blade and to assist damping vibration. On small turbochargers and the latest designs of modern turbochargers the blades are a tight fit in the wheel.

    6.) Lacing wire is used to dampen vibration, which can be a problem. The wire passes through holes in the blades and damps the vibration due to friction between the wire and blade. It is not fixed to each individual blade. The wire can pass through all the blades, crimped between individual blades to keep it located, or it can be fitted in shorter sections, fixed at one end, joining groups of about six blades. A problem with lacing wire is that it can be damaged by foreign matter, it can be subject to corrosion, and can accelerate fouling by products of combustion when burning residual fuels. Failure of blading due to cracks emanating from lacing wire holes can also be a problem. All the above can cause imbalance of the rotor.

    7.)The turbine casing is of cast iron. Some casings are water cooled which complicates the casting. Water cooled casings are necessary for turbochargers with ball and roller bearings with their own integral LO supply (to keep the LO cool). Modern turbochargers with externally lubricated journal bearings have uncooled casings. This leads to greater overall efficiency as less heat energy is rejected to cooling water and is available for the exhaust gas boiler.

    8.) The compressor impeller is of aluminium alloy or the more expensive titanium. Manufactured from a single casting it is located on the rotor shaft by splines. Aluminium impellers have a limited life, due to creep, which is dictated by the final air temperature. Often the temperature of air leaving the impeller can be as high as 200°C. The life of the impeller under these circumstances may be limited to about 70000 hours. To extend the life, air temperatures must be reduced. One way of achieving this is to draw the air from outside where the ambient air temperature is below that of the engine room. Efficient filtration and separation to remove water droplets is essential and the impeller will have to be coated to prevent corrosion accelerated by the possible presence of salt water.


    9.)The air casing is also of aluminium alloy and is in two parts.

    10.) Bearings are either of the ball or roller type or plain white metal journals. The ball and roller bearings are mounted in resilient mountings incorporating spring damping to prevent damage due to vibration. These bearings have their own integral oil pumps and oil supply, and have a limited life (8000 hrs). Plain journal bearings are lubricated from the main engine oil supply or from a separate system incorporating drain tank, cooler and pumps. Oil is supplied in sufficient quantity to cool as well as lubricate. The system may incorporate a header tank arrangement to supply oil to the bearings whilst the turbocharger comes to rest should the oil supply fail. A thrust arrangement is required to locate and hold the rotor axially in the casing. In normal operation the thrust is towards the compressor end.

    impeller%20seal.gif

    labyrinth.gif

    11.) Labyrinth seals or glands are fitted to the shaft and casing to prevent the leakage of exhaust gas into the turbine end bearing, or to prevent oil being drawn into the compressor. To assist in the sealing effect, air from the compressor volute casing is led into a space within the gland. A vent to atmosphere at the end of the labyrinth gives a guide to the efficiency of the turbine end gland. Discoloring of the oil on a rotor fitted with a roller bearing will also indicate a failure in the turbine end gland.

    12.)A labyrinth arrangement is also fitted to the back of the compressor impeller to restrict the leakage of air to the gas side
    Read More...
    1 month ago
  • (A) Auto start sequence of Boiler:

    1. Air Purging will start by boiler.
    2. The fuel oil will circulate through heater and comes to required temperature.
    3. After purging for nearly 3 minutes, the Electric ignitor will charge.
    4. The electric ignitor will make arc and the air damper will come to minimum setting , while oil pressure regulator will increase.
    5. The fire will establish and the fire eye sensor will check it and send the signal to controller that fire is establish.
    6. The controller will check other safety signals and will increase the oil and air controller to normal level.

    (B) Why boiler will shut down in auto mode

    Due to following signals from the safety transducers of the boiler the boiler will shut down in auto sequence:

    1. Boiler burner door interlock open.
    2. No fire sensed by flame eye.
    3. Low-Low water level sensed.
    4. High fuel temperature.
    Read More...
    1 month ago
  • (A) Action to be taken for scavenge fire in one engine unit only :-
    1. Inform bridge and chief engineer
    2. Reduce engine rpm with consultation of bridge.
    3. Increase the feed rate of Cylinder lub oil of that unit.
    4. Close the drain of the Scavenge.
    5. Follow the remedial action of troubleshooting and rectification as suggested by Chief engineer.

    (B)Action to be taken for scavenge fire in all the engine units :-
    1. Inform bridge and chief engineer
    2. Reduce engine rpm with consultation of bridge.
    3. Increase the feed rate of Cylinder lub oil for all the units.
    4. Ready the scavenge fire extinguishing system.
    5. Stop the engine and release the CO2 of the scavenge extinguisher system.
    6. In case fixed system is not available on very old ships an external cooling is provided to prevent distortion due to heat.
    7. Once after confirming that the fire is extinguished. The scavenge space is allowed to cool down and later opened for inspection and cleaning of the scavenge space.
    Read More...
    1 month ago
  • ANAND VARDHAN TIWARY replied to the topic 'IMMEDIATE ACTIONS REQUIRED BY EOOW' in the forum.
    (A) 1. Inform wheelhouse and Chief engineer.
    2. Reduce main engine rpm with consultation of wheelhouse.
    3. Increase Cylinder oil feed rate of the unit where scavenge fire is happening.
    4. Close the Scavenge drain
    5. Monitor the unit's scavenge space for its temperature.
    6. Take further action like stoppage of engine and doing inspection and subsequent maintenance as per the advice of the Chief Engineer.
    Read More...
    1 month ago
  • ANAND VARDHAN TIWARY replied to the topic 'Regarding Aux Boiler' in the forum.
    1 (A) High water level : The boiler water feed pump stop pumping water in boiler and Boiler burner keeps operating normally.
    (B) Low water level : The boiler water feed pump starts pumping water in boiler and Boiler burner keeps operating normally.
    (C) Extra Low water level: The boiler water feed pump keeps pumping water in boiler and Boiler burner stops.

    2. As a good practice once every alternative day the gauge glass is to be blown through.
    Read More...
    1 month ago
  • 1)
    (A) Early injection: Early injection can be caused by incorrect fuel timing, broken or wrongly set up fuel injector, incorrect fuel condition, overheating of parts around the combustion space.

    Its effect is to increase the maximum cylinder pressure. There will be an increase in combustion efficiency but the increased peak pressure leads to overload of the bearings and shock to pressure parts.

    (B)Late injection: Late injection can be caused by loss of compression, insufficient scavenging, delayed timing, incorrect fuel condition and atomisation, undercooled parts around the combustion space.

    It results in a condition called diesel knock where the flame front travels rapidly down the liner to strike the receding piston. In addition, leads to afterburning and high exhausts

    2.

    fig9-01.jpg

    3.Simultaneous Injection of Fuel and Starting Air into a Cylinder is Undesirable as it could lead to an Explosion in the Start Air System.

    4.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.
    Read More...
    1 month ago
  • ANAND VARDHAN TIWARY replied to the topic 'Centrifugal Fuel Oil separator' in the forum.
    (a)
    Purifiers have great role in ship's fuel system.It is a ring fitted at the top of disc stack from
    where water is passing out and is called gravity disc.

    Oil which is for purification may not be of
    same type every time, it is of different densities or viscosity, so the interface change, which forms between water and oil inside the purifier.

    To create the correct interface between water and oil and thus to separate water efficiently from the fuel of different densities, it is very important to select correct gravity disc size.

    (b)
    Factors that determine the size of Gravity disc are following:
    1.Selection of gravity disc depends on Specific Gravity of fuel,Temperature and feed rate

    There are 2 method to find the correct size of Dam ring
    1.Using Monogram
    2.By trial and Error method

    1.Using Monogram
    To find the correct gravity disc monograms are used on board ship which is specific for each type of purifier.

    mnogram.JPG

    Method Of Using Monogram
    For better understanding we can explain with the help of an example
    ~ < Specific gravity of treated oil 0.925 at15°C
    ~ Treating temperature 70°C
    ~ Feed rate 3000 L/h
    Selection method
    >From an intersection between falling curve I of specific gravity of 0.925 and the vertical
    line of 70°C, draw horizontal line II to reach the vertical line of 100°C.

    >Connect between the right end of line II and the point of 3000 L/h on the treating
    capacity scale using straight line III.

    >Read within which section of gravity disc Inside diameter scale the intersection made by
    line III falls.

    >For this select a gravity disc having an Inside diameter of Ø 79.

    2.By trial and Error method
    In this method use different Size of gravity disc use one by one and check the water and oil side for any leakage of oil in water side and water in oil side.

    If one particular gravity disc suits ie, no water in oil side and no water in water side which can be
    considered as a perfect one.
    Read More...
    1 month ago

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SEARCH MARITIME MEMBERS

The Global Maritime Community has many type of players and many are members of this Club. You may find them as per your need by using the filter below

Search Member by Rank / Role