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. Replacement oversize insert is usually chilled and the
cylinder head is sometimes warmed. Valve seat is pressed into the head. This
operation requires specialized 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 electrode A 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 measurement Extract bearing metal and measure thickness.2.
Measurement by means of lead wire Extract 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 and measure with a micrometer the thickness of
the lead wire thus pressed.3. Measurement with bridge gauge Apply bridge gauge
across crank journal and measure clearance between gauge and circumference of
journal. An optional bridge gauge is available. A bridge gauge is also used to
take the reading while the bottom shell is in its genuine position plus taking another
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 Ship suppliers & 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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