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 and globe 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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