Marine engineering practice
1. Explain how will you o'haul a fuel injector?
A) After the fuel valve has been disassembled then the following checks have to be done:
Ø The needle guide should be immersed in clean diesel oil and the needle taken out and checked for free movement. In case of any resistance which may be due to the presence of carbon or fuel sludge the needle may be put in and pulled out in succession many times while keeping it submerged in diesel oil. It is important to do this in a container full of clean diesel oil so the contaminants can be flushed away.
Ø After the needle guide has been cleaned, the needle should be taken almost out and then let it fall in with its own weight. A free and smooth movement with small jerks as the clearance is making way for the oil to come out is an indication that the clearances are all right and the needle guide is in good condition. It must be noted that the needle should fall fully into the seat .
Ø On the other hand if the needle falls fully in one go, then the clearances have increased and the fuel will leak past the spindle and less fuel will go in the cylinder. The needle must be inspected for any wear marks if this happens. The needle guide can be used but must be changed soon.
Ø If the needle does not go down and gets struck then it must be thoroughly cleaned again. If still there is no improvement then the needle might have become bent. Check the needle for any signs of overheating.
Ø The push rod end should be checked for any abnormal wear.
Ø The seating between the nozzle body and the valve body if damaged can be repaired by lapping with fine lapping paste. It must be noted that the lapping paste should be thoroughly flushed away with clean diesel oil and thereafter blown dry with compressed air.
Ø Check the nozzle spring for breakage, poor seating and other defects. Change if required.
Ø Check the leak off pipes, shims, packing etc for the condition. If the fuel valve is water cooled, the cooling pockets should be cleaned with compressed air.
Tests and Adjustments
Ø After the parts are cleaned and inspected the fuel valve is assembled as per the manufacturer’s instructions and thereafter tested for function and performance.
Ø The assembled fuel valve is installed on the test stand and after purging the pipe line the manual handle is operated in quick succession. The nozzle should start discharging with a sharp crackling noise at the set pressure. The pressure at which the injector is supposed to fire depends upon the manufacturer’s engine design but normally is between 250 to 350 kg/cm2 with an allowance of plus or minus 10 kg/cm2.
Ø In case the lifting pressure is not correct, it can be adjusted by the adjusting screw.
Ø The spray characteristics should be satisfactory and as per the manufacturers advice.
Ø All the holes of the injector should be firing and can be checked by a torch light or a filter paper can be folded as a cone and then the injector tested. The holes on the filter paper will show the number of holes firing. In this procedure you must be careful as the high pressure spray can enter the skin and is toxic for us.
Ø The spray angle should be as stated by the manufacturer. The atomization of the fuel should take place and solid spray should not come out.
Ø Clean diesel oil should be used for the testing purpose.
Ø In case the fuel valve is dripping the needle guide should be taken out and repaired.
2. Explain how you will change gland packing of a pump.
3. What is a SDNR valve?
A) Also called a stop disc non return valve or screw down stop and check valve. This type of check valve incorporates both the lift check andglobe valve design features. The stem is used to regulate the lift of the disc when acting as a check valve, or to hold it in the closed position.
4. How do you o'haul a globe valve?
A) Overhaul of Globe valves
When a valve is suspected not to hold or it has become tight or seized, it must be dismantled for overhaul. The overhaul procedure has been discussed below:
Ø Disassembly procedure:
Ø Remove the wheel nut and the wheel handle
Ø Open the bonnet bolts and the top portion of the valve along with the valve seat, stem etc will come out. The bottom portion of the valve will be separate.
Ø Hold the bonnet in a vice and open the gland bolts. Then loosen the gland flange and the gland bush. The valve stem should then be screwed clockwise and it would come out from below along with the valve disc.
Ø Remove the set screw of other arrangement that is securing the valve disc to the stem.
Ø Remove the gland flange, gland nut, and all the gland packings with a gland packing extractor.
Globe valve overhaul:
Ø Clean, buff, and polish all the parts.
Ø Check all the threaded parts for damage and if there is any damage on the thread then the threads must be dressed by a needle file.
Ø Check the stem for straightness. The simplest method of checking is by rolling on a flat surface, but the correct method is to put it on a lathe and center it. Thereafter with the help of a dial gauge put on a magnetic stand at a suitable point, check the distortion.
Ø Check the stem for scratches, as these can damage the gland packing. Any scratches must be removed with an emery paper or oil stone.
Ø The valve and the valve seat must be inspected and if found to be in fairly good condition, they must be ground together by using a guide for centering and a suitable grade lapping paste. A 1200 grit lapping paste would be suitable in most conditions.
Correcting Globe valve seat leakage:
Ø In case the valve seat is extensively damaged, and cannot be repaired by lapping or will take a very long time to lap, the same can be changed if it is replaceable. Some replaceable seats are screwed in, while some are force or shrink fitted. In the case it is shrink filled,the old seat can be taken out by a hammer and chisel. But when it is to be put back, the seat must be kept in the fridge room (meat room -14 deg C approx), or can be cooled by liquid nitrogen or CO2 . After cooling the seat will go in smoothly and after sometime expand and assume position. But if it if built-in type then it must be machined true using a valve seat cutter.
Ø A valve seat cutter is a special tool to cut the seats of the errant valves. It has different sizes of cutters to suit the different valves. It also has a centering guide to correctly align the tool.
Ø The seat on the valve disc can be put up on the lathe and machined true. This should be followed by lapping the two parts together.
Ø This page discusses the reassembly of the globe valve as part of an overhaul. Special mention is made of the need to correctly center the valve seat on the valve disc. In certain types of globe valves guide vanes are not present, and they could lead to wrong assembly. An improper fitting would lead to globe valve seat leakage or damage the globe valve.
Assembly of Globe Valve
Ø Clean all parts and blow dust with compressed air.Construction of Globe Valve
Ø Put the valve disc on the stem with the set screw or the arrangement provided.
Ø Put grease on the threads and screw in the stem through the yoke nut from down below. Care must be taken to put the gland nut and gland flange in correct order in between.
Ø Put back the wheel handle and the wheel nut and tighten it.
Ø Now close the valve wheel handle fully, so that the valve stem along with the valve disc extends the maximum down.
Ø Now put a correct size new gasket on the space provided on the valve body, stick it with grease or Molyslip in case of high temperature applications.
Ø Now place the valve disc on the valve seat and correctly center it. This is very important in certain valves where there is no guide.
Ø Now put the nuts and the bolts in place but do not tighten them. There would be some gap between the body and the valve bonnet. From there check again that the valve is properly centered.
Ø Now start opening the valve. As you do so, the gap between the bonnet and the body would reduce and they would come together.
Ø Now fully open the valve and tighten all the bonnet bolts in the correct sequence.
Ø Now put correct size, correctly cut, and well-greased gland packings in the stuffing box place. Care should be taken that the cut parts are together with no gaps and that the packings are staggered.
Ø Push down the gland nut and the gland flange and put in the gland bolts. The gland bolts must be slightly tightened and the correct tightening must be done in place of installation.
Ø Now close and open the valve several times and check whether it is free in movement. Check from the opening of the flanges, whether it is sitting properly on the valve seat.
Ø Paint the valve with the primer and keep it for drying.
Ø Different methods of testing after overhaul of a globe valve are used. A simple method is to fill the valve with water and use compressed air for bubble testing. The second method is to fill the chamber with compressed air and wait for a pressure drop. Globe valves are used extensively on board ships and also on offshore oil rigs and throughout other industries. It is very important for the new junior engineers and other sea going marine engineers to understand the utility and maintenance requirements of globe valves.
5. How does a gate valve work?
A) The gate valve, also known as a sluice valve, is a valve that opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is desired. The gate faces can form a wedge shape or they can be parallel. Gate valves are primarily used to permit or prevent the flow of liquids, but typical gate valves shouldn't be used for regulating flow, unless they are specifically designed for that purpose. Because of their ability to cut through liquids, gate valves are often used in the petroleum industry. For extremely thick fluids, a specialty valve often known as a knife valve is used to cut through the liquid. On opening the gate valve, the flow path is enlarged in a highly nonlinear manner with respect to percent of opening. This means that flow rate does not change evenly with stem travel. Also, a partially open gate disk tends to vibrate from the fluid flow. Most of the flow change occurs near shutoff with a relatively high fluid velocity causing disk and seat wear and eventual leakage if used to regulate flow. Typical gate valves are designed to be fully opened or closed. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low friction loss.
6. If a gate valve is stuck, what could be the reason?
7. How is a job centered on a chuck in a lathe
A) Dial gauge
8. What safety precautions will you take if working on a lathe?
Ø Always wear eye protection. The lathe can throw off sharp, hot metal chips at considerable speed as well as spin off spirals of metal that can be quite hazardous
Ø Wear short sleeve shirts, if possible, or shirts with snugly fitting cuffs if long sleeve. Loose sleeves can catch on rotating work and quickly pull your hand or arm into harm's way.
Ø Wear safety shoes
Ø Remove wrist watches, necklaces, chains and other jewelry
Ø Tie back long hair so it can't get caught in the rotating work.
Ø Always double check to make sure your work is securely clamped in the chuck or between centers before starting the lathe. Start the lathe at low speed and increase the speed gradually.
Ø Get in the habit of removing the chuck key immediately after use
Ø Keep your fingers clear of the rotating work and cutting tools
Ø Avoid reaching over the spinning chuck. For filing operations, hold the tang end of the file in your left hand so that your hand and arm are not above the spinning chuck.
Ø Never use a file with a bare tang - the tang could be forced back into your wrist or palm
9. What is a reamer? Where is it used?
A) A reamer is a metalworking tool used to create an accurate sized hole. The process is called reaming. They may be used as a hand tool or in a machine tool, such as a milling machine or drill press
10. How does a Quick closing valve work?
A) Quick closing valve is a kind of pressure reducing valve in which the an automatic process control valve for fluid pressure control is used for unmanned machinery spaces. This can be done by careful selection of valve trim, i.e. the parts of the valve that come in contact with the controlled fluid and form an actual control portion. The difference between pressure release valve and quick closing valve is that the later does not come in direct contact with the fluid it is controlling.
The lever is connected externally to a remote operating mechanism which might be pneumatic or hydraulic controlled. The controlling system has a piston which moves with the pressure of air or fluid and simultaneously moves the lever attached to it. The lever at the other end is connected externally to the spindle which is attached internally to the valve.The valve is a spring loaded valve which means that the spindle is placed through a spring which helps in re-positioning of the valve to the open position when the air or fluid pressure in controlling cylinder reduces.
All the quick closing valves are generally set in the open position.When the piston of the controlling cylinder moves up, the end of the lever which is connected to the piston moves up. As the lever is pivoted at the center, the other end of the lever moves down and pushes the spindle downwards. This closes the valve and shuts the flow of the fluid.
11. How do you reset a QC valve after operation?
A) After release, the valve can be reset according to the following procedure:
1. Turn the handwheel to the right (clockwise) until the tappet of the actuator is rested under the
stem nut.
A slight resistance can be noticed.
2. Turn the handwheel to the left (counter-clockwise) until a slight resistance is noticed.
12. Is there any difference between relief valve and safety valve?
A) DIFFERENCE BETWEEN RELIEF VALVE AND SAFETY VALVE:
Ø Releif valve is applicable in the fluid system.
safety valve is applicable in the gaseous system.
Ø Relief valve opening is directly proportional to the pressure rise.
Safety valve opening is will happen at after reaching the set
pressure.
Ø Mode of relif vlave line is again connected to the suction.
But in the safety valve is just vent-out there is no connection to
suction.
13. Explain how will you prepare for Bunkering?
Ø Are Valves and pipe lines marked for easy identification?
Ø Are valve markings correct? (Have round covers on the floor plates in the machinery space been also confirmed?)
Ø Are all deck scuppers effectively plugged? (Are wooden plugs, if any then cemented up?)
Ø Has it been confirmed that no deficit, crack, corrosion, and the like exist on the pipe line to be used?
Ø Have a leak test to the pipe line by an air pressure of 5 kg/cm2 or under been carried out? (To be entered the date of last testing in remark column )
Ø Have operation of remote valves and level gauges used in bunkering been confirmed? And also accuracy of remote gauging system verified?(if fitted)
Ø Is bilge line valves fully closed and secured?
Ø Are all the pressure gauges to be used working satisfactorily?
Ø Are all thermometers fitted in manifold working satisfactorily?
Ø Alarm setting on overfill alarm accurate & operational?(if fitted)
14. How do you set tappet clearance?
Tappet clearance is taken to ensure positive closing of the valve & for thermal expansion of the valve.
Taking all safety precautions.(See Ans. 1)
Make sure the piston is on TDC.
i. From the marking on the flywheel.
ii. From the fuel cam.
iii. Push rod should be free.
Make sure the engine has cooled down.
Loosen the lock nut of the rocker arm.
Now adjust the tappet clearance between the rocker arm & valve stem by tightening or loosing the nut below the lock nut.
If tappet clearance is less:
i. Valve will open early & close late
ii. Air induced through inlet valve may leak out. So, less air for combustion.
iii. Power will be reduced.
iv. Fuel consumption will increase, engine may become unbalanced, exhaust temp. will be very high.
v. In worst condition, valve may remain open, resulting in loss of compression pressure, burning of exhaust valve, T/C fouling will increase.
If tappet clearance is more:
i. Valve will open late & close early.
ii. Lesser heat energy to T/C, so reduction in scavenge air & hence power.
iii. No proper removal of gases.
iv. Hammering of valve stem-may cause damage to valve stem.
15. What are the steps to take after a blackout at sea?
In case of Blackout following precautions and actions should be taken:
a. Never panic in such situation, be calm and composed. Emergency generator will restore the power in no time.
b. Inform Officer on bridge briefly about the condition.
c. Call for man power and inform the chief engineer.
d. If the main propulsion plant is running, bring the fuel lever to zero position.
e. Close the feed of the running purifier to avoid overflow and wastage of fuel.
f. If auxiliary boiler was running, shut the main steam stop valve to maintain the steam pressure.
g. Find out the problem and reason for blackout and rectify the same.
h. Before starting the generator set, start the pre- lubrication priming pump if the supply for the same is given from the emergency generator; if not, then use manual priming handle (provided in some generator).
i. Start the generator and take it on load. Then immediately start the main engine lube oil pump and main engine jacket water pump.
j. Reset breakers and start all the other required machinery and system. Reset breakers that are included in preferential tripping sequence. (Non-essential machinery).
16. How do you pressure test a fuel valve?
A) For exact pressure a slow kick has to be given to avoid fluctuation in pressure gauge
17. How will you replace an exhaust valve seat?
Replacement of valve seat inserts is done by cutting out the old insert and machining an oversize insert bore. Replacementoversize insert is usually chilled and the cylinder head is sometimeswarmed. Valve seat is pressed into the head. This operation requiresspecialized machine shop equipment
18. How do you install a bearing on a shaft?
A) We ensure the shafts are free of debris and high spots visually, any burs are emery clothed out. The bearings are pressed on with a hydraulic cylinder using slow but steady pressure, the shaft is dry although the inner portion of the bearing is coated with a thin layer of grease. The hydraulic pressure is being applied to the inner race of the bearing transferred though a properly machined sleeve.
Ø Heating bearing & freezing shaft
19. How do you specify pipe size?
A) The numbers and letters on a bearing are usually the manufacturers part number. This allows the maker to quickly identify which particular bearing it is. A typical producer of bearing would make many different kind ans sizes and from different materials
20. What is the common size between different schedules of a pipe?
21. If an A/E does not start what will be your action?
Engine not starting on Air:-
a. Low air bottle pressure or air line valve may be shut.
b. Air bottle isolating valve or automatic valve or distributor not functioning.
c. Control air valves faulty or less control air pressure.
d. Start air automatic valve jammed.
e. Turning gear engaged.
f. Reversing has not taken place completely.
g. Control valve for fuel or start is not in it’s end position.
h. Bursting diaphragm on start air line damaged.
i. Fuel lever on maneuvering stand not on remote mode.
j. Auxiliary blower not running or not on ‘auto’ mode.
k. Emergency stop has activated.
l. Interlock is operated.
m. Cylinder air start valve defective or sticky.
n. Piston not in firing mode.
Engine not starting on fuel:
a. Less fuel in service tank.
b. Fuel filter is chocked.
c. Fuel supply pumps not delivering required pressure. Or fuel pump tripped.
d. Fuel level on local maneuvering stand, is not on remote stand.
e. Fuel rack stuck.
f. Fuel pump malfunctioning, jammed plunger.
g. Injector nozzle needle sticking or holes blocked.
h. Compression pressure is too low due to broken piston ring or exhaust valve not closing properly.
i. Fuel pump relief valve leaking.
j. Start air pressure insufficient to turn the engine fast enough.
22. Your action if T/C is surging?
Turbo charger surging may be defined as a high pitch vibration of audible level coming from the blower end or compressor end of the turbocharger. Whenever the breakdown of gas flow takes place, a reversal of scavenge air takes place through diffuser and impeller blades into the blower side which causes surging.Surging is to be avoided as it interferes with the combustion in the main engine and may cause damage to the thrust bearings.
Causes of Turbocharger Surging
The following are the causes of turbocharger surging:
Ø Improper power distribution between the main engine cylinders may cause turbocharger surging as one unit is producing more power and other is producing less. Due to this the air consumption required by both the turbochargers differs, which leads to surging.
Ø Fouled compressor on turbine side – In this case if the inlet filters are dirty then enough air can not be supplied for combustion, which leads to surging. Similarly if the turbine side is also dirty i. e nozzle, blades etc enough air can not be produced for combustion.
Ø Highly fouled exhaust i.e. economizer, if fitted may cause back pressure in the turbocharger and thus finally lead to surging.
Ø Bad weather – This is one more reason for surging. Due to bad weather the engine suddenly starts racing and sudden load change takes place. This happens because during bad weather or pitching the propeller moves in and out of the water, causing the change in load on the engine.
Ø Therefore, the turbochargers are needed to be matched properly with the engine air consumption rate and pressure across the operating range of the engine and they should not fall in the surge limits.
Prevent Turbocharger SurgingThe following are the ways to prevent turbocharger surging. However, it is to note that some points may vary with design and construction of the turbocharger.
Ø Keep the turbocharger intake filter clean.
Ø Water-wash the turbine and the compressor side of the turbocharger.
Ø Proper maintenance and checks should be done on turbocharger periodically.
Ø Soot blow should be done from time to time in case of economizer or exhaust boiler.
Ø Indicator cards to be taken to assess cylinder and power distribution of individual units.
23. Why is a Steam trap used in condensate return lines?
A steam trap is a special type of valve which prevents the passage of steam but allows condensate through. It works automatically and is used in steam heating line to drain condensate without passing any steam. The benefit gained with steam trap is that steam contained in the heating line until it condenses, thus giving up all the latent heat. There three main type of seam traps
1) Mechanical traps
2) Thermostatic traps
3) Thermodynamic traps
24. How is gas cutting done?
A) In oxy-fuel welding, a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. The molten pool is generally supplied with additional metal called filler. Filler material depends upon the metals to be welded.
In oxy-fuel cutting, a cutting torch is used to heat metal to kindling temperature. A stream of oxygen is then trained on the metal, and metal burns in that oxygen and then flows out of the cut (kerf) as an oxide slag.
Torches that do not mix fuel with oxygen (combining, instead, atmospheric air) are not considered oxy-fuel torches and can typically be identified by a single tank (Oxy-fuel welding/cutting requires two isolated supplies, fuel and oxygen). Most metals cannot be melted with a single-tank torch. As such, single-tank torches are typically used only for soldering and brazing, rather than welding.
25. How many valves are there on a gas-cutting torch?
Three
26. How do you light a gas-cutting torch and adjust the flame?
A) Crack open the gas valve light it with lighter and then open and adjust the oxygen valve
27. How do you set up a new pipe for welding?
Ø File the edges fo the pipe when both the piecies kept togather makeing “V”
Ø Maintaining minimum root gap tag the pipe at three four places
Ø Clean the slag
Ø Now star welding (welding to be done in one direction)
Ø Let the weld cool down remove the slag
Ø Check the weld of splatter blowhole and proper root penetration.
28. What is GPR/GPO/LH electrodes?
Gpr electrode:- High recovery rutile type electrodes for unalloyed steels. Easy to use in the horizontal position with a speed of up to 50 cm/min., and a throat thickness up to 3.5 - 6 mm in one layer. Self-releasing slag. Also suited for steels protected with zinc- or iron-oxide based primers.
Gpo electrode:-General Purpose Organic-rutile coated electrodes for unalloyd steels. Easily weldable in all positions including vertical down. Suitable for bridging large gaps. Excellent for all-purpose repair welding of mild steel
LH electrode:-Low hydrogen electrodeA covered electrode used in arc welding that provides an atmosphere low in hydrogen
29. How do you select the correct current setting for welding?
Ø Identify the type of welding technique that requires the use of electric currents to start the arc using a welding rod --- for example, electric arc welding.
Ø Determine the kind of material you will be welding in order to choose the appropriate welding rod since they must be of the same material make.
Ø Choose the type of welding rod based on the material to be welded, taking into consideration the diameter, electrical conductivity and possibly the tensile strength that is stamped on the electrode
Ø Observe the last two digits together "1/8 E60XX" to indicate the type of coating used on the welding rod and the welding current that can be used with it. Use Direct Current (DC) straight, (DC -) DC reverse (DC+) or Alternate Current (A.C) as stamped on the welding rod to choose your amperage.
Ø Regulate the "Current Selector" or a comparable option to select the amp range once you've identified all the necessary parameters for the weld
30. Crank pin brg clearance
A) Telescopic feeler gauge
In engines like MAN B&W, this is the most common method used to measure the bearing clearance of the top shell. In this method there is no need to remove any connection or keep for measuring the clearance.
The telescopic gauge is inserted between the gap of the crank web and the bearing keep. When the tip reaches the shell top, the feeler is inserted between the shell and the pin to check the clearance.
31) Welding defects?
Common weld defects include:
i. Lack of fusion
ii. Lack of penetration or excess penetration
iii. Porosity
iv. Inclusions
v. Cracking
vi. Undercut
vii. Lamellar tearing
32) Bridge gauge main brg clearance
MEASURING CLEARANCES
Metal thickness measurementExtract bearing metal and measure thickness.2. Measurement by means of lead wireExtract main bearing cap and put a soft lead wire (0.5mm) on upper part of crankshaft. Then replace cap and tighten to prescribed torque. Remove cap andmeasure with a micrometer the thickness of the lead wire thus pressed.3. Measurement with bridge gaugeApply bridge gauge across crank journal and measure clearance between gauge andcircumference of journal. An optional bridge gauge is available. A bridge gauge is alsoused to take the reading while the bottom shell is in its genuine position plus takinganother reading after removing the shell and seeing the difference between them.
33) How does a Stud extractor work?
A) The stud extractor is a versatile tool designed for the removal or insertion of threaded studs into blind stud holes. Clamping force on the end of the stud is generated by a closing collet designed to grip the minor diameter of the thread without inflicting damage on the thread root.
The principal operation entails threading the collet on to the stud until it is bottomed out. A multi-jack bolt tensioner is tightened with an allen key forcing the tapered ring down over the collet. The taper produces an internal radial clamping force that compresses the collet onto the stud. The Stud Runner grips so tightly that a tremendous amount of torque can be applied in either direction
34) How does a chain block work?
A) A chain hoist uses gears to multiply force.
A chain hoist is operated by hand. An operator pulls the light loop chain on the side of the chain hoist. This turns a gear mechanism inside the chain hoist housing to turn the chain pulley. When this pulley turns, it raises the heavy chain which usually has a hook on the end. By pulling the light chain loop, the manual hoist is actually able to increase the force that is being applied by the heavy chain. This is caused by the gear ratios inside the manual chain hoist. The mechanical work done by the operator is the same as the work done by the heavy lifting chain.
35) What are the safeties on cargo cranes
36) What are the safeties on ER crane?
A) Overload trip.
B) Limit switch at fore & aft side.
C) Limit switch port & starboard movement.
D) Switch button have non-metallic body.
E) Emergency stop.
F) Spring loaded or band brake
G) Fail safe arrangement
37) How does a chain block work?
A chain hoist is operated by hand. An operator will pull down on one of the chain loops on one side of the chain. This will turn a pulley mechanism inside the chain hoist housing. When this pulley turns, it will lift up the end of the other chain which usually has a hook on the end. By pulling down on one chain, the manual hoist is actually able to increase the mechanical work that is being done. This is caused by the gear ratio inside the manual chain hoist.
38) How is the load controlled during lowering?
39) How is the E/R crane load tested
40) Fuel valve not coming out?
41) Setting exhaust valve timing
42) Pumps o'haul?
Removal of Pump for Inspection and Maintenance
1 Isolate pump electrical circuit breaker on main switch board and attach a warning notice. (Do Not Operate-Men at Work).
2. Switch off and lock pump supply at its local supply panel. Attach a warning notice to pump local supply panel.
3. Close suction and discharge valves, chain and lock hand wheels.
4. Open pump suction and discharge pipe drain valves to bilge and when water ceases to flow; crack open the pipes / pump flange joints carefully to ensure that pump has drained off and is safe for opening.
5. Fix a shackle to lifting pad eye above pump and hang chain block; ensuring SWL of block, slings and shackles are satisfactory.
6. Use a center-punch to match/mark coupling and casing, then remove the coupling bolts.
7. Disconnect, fix i/d tag and remove motor supply cables; taping over bare ends with insulating tape.
8. Connect shackle and sling to motor eyebolt and lift motor clear of pump using overhead chain block. Lay motor on its side out of harm’s way, protecting machined surfaces on both pump and motor coupling halves against damage. (Cardboard and masking tape is quick and efficient method.)
9. Disconnect all external fittings from pump casing e.g. cooling pipe, pressure gauge, oil reservoirs and air cock.
10. Remove bolting from top cover and remove cover. Scrape off old gasket and check mating surfaces, and renew gasket on assembly. (Light smear of grease on gasket / faces)
11. The pump shaft with impeller can be lifted out of casing.
12. Dismantle the impeller, and remove the wear ring.
13. Remove the gland packing and disregard; replacing it on rebuild. Remember to cut ends of packing at 45° and stagger joints when repacking gland.
Inspection Procedure for Pump and Motor
Pump
1. Impeller, pump shaft and internal volute/casing can now be inspected for erosion, pitting and wear.
2. If required rectify pitting or erosion in the impeller and casing with two – part alloy epoxy putty. (See my article in the Reference section)
3. Check main drive shaft bearings and thrust bearings for wear and replace if required.
4. Check wear ring clearance using feeler gauges; in my day at sea it was general practice is to replace with new rings at major overhaul.
5. Check impeller / shaft key and keyways for damage and undue wear, Unscrew impeller shaft securing nut and check threads are in satisfactory condition; retighten to manufacturers torque settings.
6. Give all parts a good clean removing any dirt/ medium residue before re- assembly using new parts as required.
7. Enter date of overhaul and parts renewed in the pump maintenance record card.
Drive Motor
1. Grip motor drive shaft /coupling firmly and check for excess axial and longitudinal movement. Rotate shaft at speed by hand, allowing it to run to a stop whilst listening for excess noise from bearings. Any doubt on either counts, the bearings should be replaced.
2. Megger check motor windings to ensure no dampness is present and windings are in good condition. Any suspect readings indicate a full motor strip to check condition of rotor and stator.
3. If these checks are satisfactory, grease bearings as required. Some bearings are now sealed for life and will not require greasing.
Procedure to Start the Pump
1. Unlock and remove chains from inlet/outlet valve wheels and open both valves full.
2. Open air cock and expel air from line and pump while checking for any leaks
3. Turn the shaft coupling and ensure shaft is free to rotate.
4. Reconnect motor.
5. Remove danger notices from pump power supplies and reinstate breakers.
6. Start and record current drawn by the motor under starting and running conditions. Check and record the discharge pressure.
45) Type of drill bits?
A) Spade, lip and spur (brad point), masonry bit and twist drill bits
46) Types of threads?
i. BSW- Bristish Standard whit worth
II. BSF – Britsh standard fine
III. BA – British Assosiation
IV. BSP – British Standard Pipe
V. AS– American standard
According to shape
i. V- shape
ii. Square thread
iii. Buttress thread
iv. Acme thread
v. Knuckle thread
47)Pipe schedule?
A) Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures. Pipe size is specified with two non-dimensional numbers: a nominal pipe size (NPS) for diameter based on inches, and a schedule (Sched. or Sch.) for wall thickness. NPS is often incorrectly called National Pipe Size, due to confusion with national pipe thread (NPT).
48) Important dimensions of flanges? Types of flanges?
A) OD, ID, THICKNESS, BOLT HOLE DIAMETER
Type of flanges
Ø Welding Neck flange
Ø Slip On flange
Ø Socket Weld flange
Ø Lap Joint flange
Ø Stub End
Ø Threaded flange
Ø Blind flange
49) Indications of scavenge fire? What action will you take?
Causes of Scavenge Fire
Ø Blow past of combustion products caused by leaky, sticky or broken piston rings, worn out liner, faulty cylinder lubrication, or insufficient axial clearance of the piston rings.
Ø Overheated piston dissipates heat to the under piston area caused by faulty atomization and injection pressure, faulty fuel pump timing, loss of compression, engine overload, failure of coolant circulation or insufficient cooling due to formation of scale.
Ø Blow back of exhaust gases caused by exhaust back pressure or deposits on exhaust ports, fouling of grid before turbine inlet, fouling of turbine blades, choking of EGB or economiser gas outlet.
Ø Presence of fuel oil in the scavenge spaces due to defective fuel injectors, incorrect pressure setting of injectors or fuel particles landing on the cylinder liner due to excessive penetration.
Ø Excessive cylinder lubrication which is drained down to scavenge spaces.
Ø Oxygen is plenty during engine operation.
Ø Fouled scavenge manifold.
Indication of Scavenge Fire
Ø Engine revolution drops as the power generation in the affected cylinder is reduced.
Ø Unstable operation of Turbo charger and may cause surging.
Ø Exhaust temperature of the affected cylinder increases, as the cylinder is not receiving fresh air.
Ø Black smoke with exhaust due to incomplete combustion in that unit.
Ø Discharging of spark, flame or smokes through drain cocks from scavenge air boxes.
Ø Rise of pressure and temperature of air in the air box below the piston.
Ø Visible evidence of fire if a transparent window is fitted.
Ø Cooling water outlet temperature of the affected unit is increased.
Action to be Taken
Ø Inform bridge and reduce the speed.
Ø Cut of fuel supply to the affected unit and shut off valves.
Ø Cylinder lubrication is increased.
Ø Coolant flow through jacket and piston is maintained.
Ø Drains to be shut to prevent flow of spark in engine room.
Ø Keep clear of scavenge space relief valve to prevent human injury
Fire should be extinguished after some time. If the fire spread in the other scavenge spaces along with the scavenge manifold, then -
Ø Inform bridge and stop the engine
Ø Stop fuel oil booster pump
Ø Open indicator cocks, engage turning gear and turn engine to prevent engine seizure
Ø Normal engine cooling and lubrication are maintained
Ø Scavenge air duct flap valve before engine is to be shut
Ø Release the smothering gases (Steam or CO2) to extinguish fire
Ø Before opening scavenge door ventilate the space thoroughly if CO2 is released.
Inspection after Scavenge Fire
Ø Intense fire can cause distortion and may upset piston alignment
Ø Check by turning the engine and watch movement of piston in the liner, check for any occurrence of binding at part of stroke (Binding indicates misalignment of piston)
Ø Check spring on scavenge space relief device, if the device was near the set of fire
Ø Piston rod packing spring also should be checked, which may have become weakened by overheating
Ø Check piston rings and liner for any distortion or reddish burning mark
Ø Check diaphragm and frame near affected part
Ø Check guides and guide shoes
Ø Check tension of tie bolts
50) Where are wear rings used? What is their purpose?
Wear rings are sacrificial components installed on the casing and impeller to inhibit fluid from recirculating back to suction from the discharge. They provide a renewable restriction between a closed impeller and the casing. Wear rings are often installed on both the front and back of the impeller. When wear rings are installed on the back of the impeller, another set of rings is installed in the backcover.
Wear rings act as the seal between the casing and the impeller.
51) Boiler gauge glass? Reflex type? Blow through procedure?
A) Procedure:
i. Make sure drain line is clear
ii. Close the steam outlet valve.
iii. Close the water outlet valve.
iv. Open the drain valve.
v. Open the water out valve & let water flow thru it and close the valve after blowing down with water.
vi. Open the steam out valve and blow thru with steam.
vii. Close steam valve.
viii. Close the drain valve.
ix. Now, open the water side valve.
x. Let water fill up 3/4th gauge glass.
xi. Open the steam valve slowly.
52) ISSA code book?
A) International Shipsuppliers & Services Association code book. encoding the international marine materials
53) SG hunting gear?
54) Axe blade? How fitted?
55) SCBA pressure testing
Low Pressure (2216 psig) and High Pressure (4500 psig)
Parts to be tested
1 Test pressure gauge for cylinder pressure
2 Magnehelic gauge for low pressure testing
3 Test pressure gauge for medium pressure
4 Test hose 6 ft. (See Note)
5 Test bladder
6 Vacuum/Pressure bulb
7 Hose clamps (2)
8 Rubber stopper
9 Quick disconnect connections (2)
10 Tubing tee
11 Connecting socket
I2 Knuckle thread test assembly
I3 Test piece
14 Medium pressure line
15 Test piece
16 O-Ring
17 Flow meter
18 Flow meter adapter
56) Welding surface preparation
1) clean the metal surface with wire remove all oil rust or any other partical from the surface of the metal
2) file the surface to be welded making V-SHAPE
57) No water in gauge glass
58) Flaring tool
A) Flaring tool are adaptive mechanisms used in pipe fittings. They accept pliable metal and expand the ends of pipes section as needed, sothe pipe can fit to the next section.
59) what is ermato joint
A) A body with conical seat, a nut and ferrule when assembled behind it, tube form ajoint on progressive tightening the nut on the body the ferrule bites into the outer surface of the tube, thereby ensuring leak proof joint at high operating pressure.
60) Why copper gasket is annealed?
61) how will supervise a lube oil filter cleaning
A) Bucket filter oil enter from Centre of filter and flows out
1. When pr. Diff. increases across the filter it indication filter is chocked
2. change over to standby filter
3. open top cover
4. remove bucket from the casing
5. dip/clean it with diesel or kerosene
6. clean it with cotton
7. blow air in the opposite to direction of the flow, use cotton as a screen behind it.
62)what precautions have to taken during cleaning of SW line filters?
63) what is dead man’s alarm?
A) dead man alarm system is designed to monitor e/r activity and alert the c/e and other engineers if the e/r becomes unattended.
64) what will be action if your reliever appears drunk?
A) Refuse to change over the watch and inform person in charge.
65) Your oiler appears drunk what will be your action
66) compound gauge
A) a compound gauge is a press. Guage that displays both –ve and +ve gauge press. Measurement. Gauge press is a measurement of press. Relative to ambient pr.
67) Pump shaft broken Suggest repair?
68) what is gear back lash?
A) back lash can be defined as a rotational arc clearance formed between a pair of mounted gears. A back lash (clearance) to any gear set for checking damage caused by gear tooth interference. Lack of back lash causes following problem.
Ø Noise
Ø Overloading
Ø Overheating of gears and bearing
Ø Seizing and failure
69) What are the different types of gear seen in ship?
Ø Spur gear
Ø Helical gear
Ø Worm and worm wheel
Ø Rack and pinion
Ø Bevel gear
70) what is hunting tooth
A) An extra odd tooth, gear wheel designed to ensure the same teeth do not mesh together, thus reducing wear.
71) Why is gear oil different from others?
A) Because high pressure exists between the gears, which makes it difficult to substance boundary lubrication that why high pressure lube oil is used in gear .
72) what are the different type of taps and dies?
A) Type of taps
Ø Tapper tap
Ø Plug tap
Ø Bottoming tap
Type of dies
Ø According to press opration
Ø Cutting dies
Ø Forming dies
According to opration
Ø Simple die
Ø Compound die
Ø Combination die
Ø Progressive die
Ø Multiple die
Ø Transfer die
73) why do we check ullage? How to calculate liquid quantity?
A) Because when ship rolls it becomes difficult to accurate readings
74) What are VRF
75) What do you check while opening piston
Ø Remove all carbon and varnish from piston.
Ø Using ring groove cleaner, clean all deposits from ring grooves. Ensure all deposits are cleaned from ring grooves to prevent ring breakage or sticking. DO NOT attempt to clean pistons using wire brush.
Ø Inspect pistons for nicks, scoring, cracks or damage in ring areas.
Ø Connecting rod should be checked for cracks using Magna flux procedure. Piston diameter must be measured in manufacturers specified area.
Ø Using telescopic gauge and micrometer, measure piston pin bore of piston in 2 areas, 90 degrees apart. This is done to check diameter and out-of-round
Ø Connecting rod I.D. and out-of-round must be within specification. Measure piston pin bore I.D. and piston pin O.D. All components must be within specification.
Ø Connecting rod length must be measured from center of crankshaft journal inside diameter to center of piston pin bushing using proper caliper.
Ø Connecting rods should be checked for bent or twisted condition.
Ø Piston rings must be checked for side clearance and end gap. To check end gap, install piston ring in cylinder which it is to be installed. Using an inverted piston, push ring to bottom of cylinder in smallest cylinder diameter.Using feeler gauge, check ring end gap
76) stating air getting hot your action?
77) Draw LS of ball bearing fitted on shaft
78) What is lip seal
A) Marine Auxiliary Machinery MCGEORGE pg no 268
79) mechanical seal
A)Marine Auxiliary Machinery MCGEORGE pg no 149
80) Exhaust below sketch
84) What is dress coupling
A dresser coupling is a device used to repair a leaking pipe.
85) what is bumping clearance? How do you measure it?
A) Clearance volume or bumping clearance is the space between the top of the piston and the cylinder head of an air compressor. This clearance is an important aspect of the compressors and should be as less as practically possible to improve the volumetric efficiency of the compressor. The clearance volume should not be too less or too more. Moreover, it affects the efficiency of the machinery and thus should be checked at regular intervals of time.
Significance and Effects of Bumping Clearance
In an air compressor, when the discharge valve closes in the end of the compression cycle, a small amount of high pressure air is trapped in the clearance volume.
Before again taking suction, the air trapped in the clearance volume must expand below the suction pressure i.e. below the atmospheric pressure.
The expansion of this trapped air in the clearance volume causes effective loss of stroke due to which the volumetric efficiency of compressor drops. Therefore, the clearance volume has a significant effect on the efficiency of the compressor.
Effects Due to Less Clearance
Small clearance volume may result in piston banging or colliding to the cylinder head.
This is dangerous when the compressor when is running in unloaded condition without any resistance to the movement of the piston.
Effects Due to Large Clearance
Large bumping clearance retards the formation of vacuum on the suction stroke and thus less air is drawn inside for compression and accordingly the weight of the air delivered is reduced proportional to the clearance volume.
Compressor has to run for a longer period to provide the necessary compression pressure.
Reasons for Change in Clearance Volume
During overhauls of the air compressor, if the gasket fitted between the cylinder head joints is of the wrong type, then the bumping clearance will increase, resulting in wear down of bottom bearings or wrong bearings are put in place.
How Bumping Clearance is checked?
Bumping clearance is checked by putting a lead ball or plastic gauges over the piston and then turning the compressor one revolution by hand.
By doing this the lead ball will compress and the thickness obtained is the clearance volume.
This thickness is measured with vernier caliper or micrometer and is then compared with the manufacturer’s value. Adjustments are made in case there is an offset in the value.
Adjustment of bumping clearance
Bumping clearance can be adjusted with the help of inserting shims (thin metallic plates) in the bottom bearings. Inserting shims will move the connecting rod and the piston which will change the clearance.
What should be the Bumping Clearance?
Generally bumping clearance depends on the manufacturer but as a thumb rule it should be between 0.5% to 1% of the bore of the cylinder.
87) Why centrifugal pump started with its discharge valve shut?
A) Pump with close discharge valve .This is because of the high column head it has to withstand .If you open the discharge valve and start up the pump, then pump has to withstand the high torque which may damage the pump's motor or prime mover.Be watchful and as soon as the flow is achieved and pressure is there , then start gradually opening the discharge valve.
88) How will align a pump to it motor
89) what check you will make on bottom end bearing boolts?
Ø Proper Surface Finish
Ø Proper Tightening
Ø Check the bolt for cracks, damage, etc.
Ø Locking of the nuts should be checked thoroughly.
Ø Sounding testing by hammer to identify internal flaws and cracks. It should be healthy noise.
90) How will measure ovality of crank pin
A) With reference to the engine manf. tolerances and record sheet, using a calibrated micrometer. Bottom end bearing is removed from crankpin / piston removed. Surface wiped clean. Then at the specified points in the record sheet, measure the diameter. Normally at least 0, 45, 90, 135 deg. with ref to TDC and 5 equal distance locations across the pin.
Normally wear would be seen at the top (highest loaded point), and may require grinding undersize to remove ovality, followed by thorough oil flushing / locate source of contamination.
91) How hydraulic tightening works
92) Why jack turned back a little while slacking
93) What will you check in up space inspection?
94) How will do crack case inspection.
Safety
1. After stopping the engine shut off all pump
2. Post placards for men at work at starting panel
3. Isolate the engine from stand by mode
4. Shut off lube oil priming pump
5. Open indicator cock
6. Allow engine to cool down
7. Wear all protective clothing
8. Light bulbs should be covered with globe and protective caging
Timing Gear
1. Check the condition of the gear tooth for corrosion pitting broken tooth excessive back lash etc
2. Check lubricating spray nozzle for clogging or breakage
3. Check for condition of cam rollers should be free to rotate on pin surface finish of rollers ans cams
4. All the thee cams for each unit to be checked
5. Check lubrication of each cam
Running gear
1. Check tightening and locking of bottom end bearing bolt use testing hammer
2. Check axial displacement of connecting rod
3. If the crack shaft is buildup type the check the reference mark are in proper position
4. Check for any leaks of water from liner o ring
5. Lube oil pipe to started and check for uniform oil flow
Oil system and pipes
1. If the engine is of dry sump type check the condition of grid and see that if it is clear of any obstructions
2. Check pip flanges of distribution pipe
3. Check for proper clamping
4. Distribution pipes to checked for proper tightness and not leaking
5. Check underside of each bearing for any metal particles including crankcase
6. Check condition of crankcase painting it should not peel off otherwise it indicates acidic mixture of L/o
7. Check for flow of oil from indivial bearing by starting the lube oil p/p
95) Ship side valve leaking in engine room what will you do
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