What is a thermostatic expansion valve?
This is a regulator through which the refrigerant is metered
from the high pressure side to the low pressure side of the system. The
pressure drop causes the evaporating temperature (saturation temp.) of the refrigerant
to fall below that of the evaporator.
a. Avoids
liquid refrigerant return to the compressor suction.
b. Automatic
expansion control and maintain 6 ~ 7 degree superheat.
7. What is a
Coalescer?
A device consisting of a material whose surface provokes
coalescence. The process of combining of larger droplets of a liquid like oil
into larger droplets is called coalescing.
8. Why is there
a starting air overlap provided in a diesel engine?
a. To give a
positive starting in correct direction.
b. Starting
ability from any position.
c. If any one
of the valve is malfunctioning, Engine can still be started.
9. What is the
significance of firing order?
a. Balancing of
primary and secondary inertia forces.
b. To assist
the exhaust grouping.
c. For distribution
of stress over the length of crankshaft and optimum bearing loading.
d. A firing
interval for even turning moment.
11. Explain the
functions of lube oil in refrigeration system
a. Lubrication
b. Seal the
clearance spaces between the discharge and suction sides of the compressor.
c. Act as a
coolant.
d. Actuate
capacity control.
e. Dampen the
noise generated by the compressor.
12. What are the
various windlass safeties?
ELECTRIC:
a. Electromagnetic
brake.
b. Motor
overload protection.
c. Short
circuit protection.
d. Restart
delay timer.
e. A Restart
stop.
MANUAL:
a. Manual brake
/ mech. Brake.
b. Cable
stopper.
c. Slipping
clutch (torque limiter).
d. Relief
valve.
13. What are the
steering gear motor safeties?
a. Overload
alarm.
b. 200% insulation
in motor.
c. High
temperature alarm.
d. Self
starting after power failure.
e. Short
circuit trip.
f. If the ship
has an earthed neutral, then the motor neutral is earthed through a
transformer.
g. Phase
failure alarm.
h. One of the
steering motor is fed from the emergency bus.
Hydraulic side there is two trips
a. Low level
cutout
b. High lube
oil temperature cutout.
14. What are the
overhead crane safeties?
Current to motor's field coils passes through solenoid coil
of a brake which is magnetized and holds a brake against spring and releases
the rotor. Incase of power failure the solenoid is demagnetized and brake is applied.
SAFETY:
a. Limit switch
on the f'wd, aft, port, s'tbd, hoisting and lowering prevents movements more than
the allowed limits.
b. Overload
trip.
c. Dead man's
handle.
d. Guards over
the pulley.
e. Locking
device on the lifting hook.
f. Mechanical
locking (to avoid crane movement during heavy weather)
15. What is a
critical pressure?
It is the pressure at which gas will just liquefy at its
critical temperature.
16. What is a
critical temperature?
It is the temperature above which the gas cannot be liquefied
under isothermal compression.
17. What are the
air bottle safeties?
a. Relief valve
b. Fusible plug
c. Drain
d. Low pressure
alarm
20. What are the
causes of turbocharger surging?
a. Rapid
variation (reduction) in load.
b. Chocked
exhaust and air passage like scavenge ports, valve or air cooler etc.
c. Abnormal
fuel system like a unit misfiring.
d. Chocked air suction filter, fouling of
the turbocharger, unbalanced output from the engine, damaged exhaust valve,
scavenge fire.
22. What is the
normal relief valve setting of cylinder head in a diesel engine?
10 ~ 14.5% more than the working pressure. about 120 bar (some
what higher than maximum pressure)
23. State the
advantages of uniflow scavenging
a. Simple liner
construction
b. Long skirt
(for piston) not required
c. Stroke
length can be increased
d. High
scavenging efficiency
e. High thermal
efficiency
f. Low grade
of fuel can be burnt
g. Uniform wear
of piston rings and liner
h. Less thermal
stresses
i. Less
intermixing of scavenging air with the exhaust gas
j. Exhaust valve can be made to open late
- more work, close early - scavenge air is more utilized.
28. What are the
reasons for black smoke from a diesel engine?
a. Poor
combustion due to faulty injection system
b. Low
compression
c. Insufficient
scavenging air
d. Fouled
exhaust system
e. Broken
piston rings
f. Ineffective
lube oil seal
g. After burning,
bad fuel and other fuel assisted faults
h. Faulty
cylinder lubrication
i. During
starting, it is inevitable as the engine maker sets the starting fuel index to
a fixed value. At this index there is insufficient air, low piston speed, cold
combustion chamber, low fuel injection pressure etc., each compounding the
cause for black smoke
29. What are the
critical speed effects?
Resonance, Torsional vibration, fatigue failure of components
Can be remedied by:
a. Detuners
b. Vibration
dampers
c. Electric
vibration compensator unit
33 what is critical speed?
Critical speed is when the natural frequency matches the
operating frequency.
30. What are the
types of vibration in a diesel engine and which is the most damaging?
Types of vibration:
a. Linear vibration
b. Torsional
vibration
c. Resonant
vibrations involving any two of the above or may be combinational
48. Why are the
CO2 bottles provided with dip tubes?
It is to ensure that only liquid is drawn during release.
The liquid expands after the nozzles and assumes the gaseous state. This will
prevent co2 freezing and blocking the nozzle
Also it achieves the 85% discharge in 2 Minutes as liquid
part represents a large volume of gas
The materials used in its construction are copper, stainless
steel
51. What are the
causes of a centrifugal pump reduced output?
a. Friction and leakage losses, loss of
suction head, chocked suction filter, worn out wear ring, air ingress in the
suction side
b. Low voltage
is applied to the pump motor
c. Cavitations
on the impeller
d. Bad
maintenance, incorrect fixing up of the parts after overhaul
59. What is the
function of the driers in the refrigeration system?
The filter/drier is installed in the main liquid line of the
system to absorb any moisture present in the refrigerant. It consists of
activated alumina or silica gel in a renewable cartridge. It also accommodates
the charging connection
65. What are the
advantages and disadvantages of the synthetic lube oils?
Advantages:
a. Better low
temperature fluidity and pump ability,due to nil wax content
b. Better oil
retention at high temperatures
c. Lower
friction losses
d. Reduced
thickening of the oil in service due to oxidation
e. Lower deposits at higher temperature
due to resistance to oxidation properties and thermal stability
Disadvantages:
a. Increased
cost of the lube oil (about 6~12 times)
b. Poor
availability
Uses:
a. Air
compressors
b. Purifiers
c. Hydraulic
units
74. What are the
environmental problems with the use
of CFCs?
a. CFC released
into the atmosphere are broken down by
pyrolysis to release chlorine atoms which
catalytically destroy ozone layer.(this layer in the
stratosphere acts as a filter to the UV radiation from
the sun)
b. Furthermore
CFCs along with other greenhouse gases
inhibit radiation from the earth's surface thereby
contributing to the global warming.
78. Why
intercooling is provided in an air compressor?
And why is the compression distributed into stages?
a. By employing
the interstage cooling we are trying
to achieve an isothermal compression cycle. So least
work is expended in the process.
b. The air
outlet temperature after compression is
lowered by intercooling. So oxidation of the lube oil
is prevented. Also good lubrication is achieved.
c. Lesser
deposits in the air system.
d. Intercooling
increases the air density and hence
reduced volume of the HP compression chambers is
possible.
e. It
facilitates removal of moisture by condensation
at the intercoolers.
f. To
facilitate intercooling the compression is
distributed into stages. Also even load distribution
is achieved over the cycle.
89. What are the
safeties in the fridge system?
a. HP cut out
b. Differential
lube oil pressure cutout
c. LP cutout
d. Relief valve
in the condenser
e. Belt driven
f. Cylinder
head relief valve
g. Cooling
water low flow/high temperature alarm
h. Motor
overload
i. Oil
separator
j. Drier
k. Mech. Seal
l. Unloaders
/capacity controllers
m. Non return
shut off valves
n. Sensors -
temperature, pressure
PROCEDURE OF BUNKERING
Before bunkering
The engineer in charge normally 3rd Engineer should give all
tank soundings to the Chief Engineer.
The bunker tanks to be filled should be emptied i.e. the
remaining fuel to be transferred to settling tank or unused bunker tank to
prevent mixture of bunker. This is because the properties of the bunker
received are not always the same.
The valves in the bunker pipeline should be set/open – made
ready.
Duties divided among engine personnel i.e. Oiler, Junior
Rating, 2 Engine Cadets and Duty engineer.
SOPEP- (Ship Oil Pollution Emergency Plan) items to be
prepared as standby at the bunker manifold i.e. SOPEP drum, Wilden pump with
hose attachments to suck the spillage, saw dust, rags, OSD- (Oil Spill
Dispersant) Chemical and a 9 Litres Foam Type Portable Fire Extinguisher.
During bunkering
Ensure that the scuppers are plugged
Someone should be on standby at the manifold to look out for
leakage, usually cadets.
Sounding of tanks should be taken at constant intervals,
usually by Oiler.
The engineer in charge will be controlling valves if there’s
a need to change tanks.
The stability is taken into account when receiving bunker.
The most important of all is that the sample of bunkered oil
is taken by using a special flange called “Continuous Drip Sampling Flange”.
After bunkering
The final sounding should be taken and the amount of bunker
received to be calculated.
The engineer in charge should go to the bunker barge and
check all the tanks.
When everything is satisfactory, the Chief Engineer will
sign on the bunker document from the bunker barge.
Ensure that the blank flange on the bunker manifold is
tightly bolted.
How do you detect fire on board (In engine room and
accommodation.)?
- smoke
detector
- flame
detector
- Heat
detector.
HOW TO HANDLE FIRE
F – Find
I – Isolate
R – Report
E – Extinguish
FIRE DETECTION SYSTEM
Smoke detector (Photo-electric cell)
When smoke detected, light scattered around the barrier on
to the photo-cell and an alarm is triggered.
Flame Detector (infra Red)
- Flickering
radiation from flame reach the detector lens/filter unit, which allow infra-red
ray to pass and focused upon the cell and then trigger the alarm.
Heat Detector (Bi-metal coil)
- When 2
metal strip bent forward the contact point that caused by different kind of metal
used in the strip when react to heat.
FIXED FIRE FIGHTING SYSTEM
FIRE MAIN
The diameter of the fire main is to be based on the required
capacity of the fixed main fire pump(s) and the diameter of the water service
pipes are to be sufficient to ensure an adequate supply of water for the
operation of at least one fire hose.
The wash deck line may be used as a fire main if the
requirements of this sub-Section are satisfied. All exposed water pipes for
fire-extinguishing are to be provided with drain valves for use in frosty
weather. The valves are to be located where they will not be damaged by cargo.
When the fixed main fire pump is delivering the quantity of
water required , or the fire pump described as the alternative the portable
pump , through the fire main, fire hoses and nozzles, the pressure maintained
at any hydrant is to be sufficient to produce a jet throw at any nozzle of not
less than 12 m.
CARBON DIOXIDE SYSTEM
Carbon dioxide systems are to comply with 7.1 in addition to
the remaining requirements of this sub-Section. For the purpose of this
Chapter, the volume of free carbon dioxide is to be calculated at 0.56 m3/kg.
For machinery spaces:
The quantity of carbon dioxide carried is to be sufficient
to give a minimum volume of free gas equal to the larger of:
30 per cent of the gross volume of the largest machinery
space protected, including the casing;
The fixed piping system is to be such that 85 per cent of
the gas can be discharged into the space within two minutes; and
The distribution arrangements are to be such that
approximately 15 per cent of the required quantity of carbon dioxide is led to
the bilge areas.
Two separate controls are to be provided for releasing
carbon dioxide into a protected space and each is to ensure the activation of
the alarm. One control is to be used to discharge the gas from its storage
cylinder(s). A second control is to be used for opening the valve of the
piping, which conveys the gas into the protected space. The two controls are to
be located inside a release box clearly identified for the particular space.
If the box containing the controls is to be locked, a key to
the box is to be in a break-glass type enclosure conspicuously located adjacent
to the box. There is to be a dedicated release box for each protected space, in
which personnel normally work or to which they have access, see also 7.1.7.
The space served is to be identified at the release box.
Distribution pipes for carbon dioxide are not to be smaller than 20 mm bore.
High-expansion foam systems
Any required fixed high-expansion foam system in machinery
spaces is to be capable of rapidly discharging through fixed discharge outlets
a quantity of foam sufficient to fill the greatest space to be protected at a
rate of at least 1 m in depth per minute. The quantity of foam-forming liquid
available is to be sufficient to produce a volume of foam equal to five times
the volume of the largest space to be protected.
The expansion ratio of the foam is not to exceed 1000 to 1.
Alternative arrangements and discharge rates will be permitted if equivalent
protection is achieved. Supply ducts for delivering foam, air intakes to the
foam generator and the number of foam-generating units are to be such as will
provide effective foam production and distribution.
The arrangement of the foam generator delivery ducting is to
be such that a fire in the protected space will not affect the foam-generating
equipment.
The foam generator, its sources of power supply,
foam-forming liquid, and means of controlling the system are to be readily
accessible and simple to operate and are to be grouped in as few locations as
possible at positions not likely to be cut off by fire in the protected space.
Foam concentrates carried for use in fixed foam fire-extinguishing
systems are to be of an approved type. They are to be tested at least twice
during each five-year period to verify that they remain fit for service.
Evidence in the form of a report from the foam manufacturer or an independent
laboratory will be accepted.
Pressure water-spraying systems
Any required fixed pressure water-spraying
fire-extinguishing system in machinery spaces is to be provided with spraying
nozzles of an approved type. The number and arrangement of the nozzles is to be
such as to ensure an effective average distribution of water of at least five
litres per square metre per minute in the spaces to be protected. Where
increased application rates are considered necessary, these will be specially
considered. Nozzles are to be fitted above bilges, tank tops and other areas
over which oil fuel is liable to spread and above other specific fire hazards
in the machinery spaces.
The system may be divided into sections, the distribution
valves of which are to be operated from easily accessible positions outside the
spaces to be protected and which are not to be readily cut off by fire in the
protected space.
The system is to be kept charged at the necessary pressure,
and the pump supplying the water for the system is to be put automatically into
action by a pressure drop in the system.
The pump is to be capable of simultaneously supplying, at
the necessary pressure, all sections of the system in any one compartment to be
protected. The pump and its controls are to be installed outside the space(s)
to be protected. It is not to be possible for a fire in the space(s) protected
by the water-spraying system to put the system out of action.
The pump may be driven by independent internal combustion
type machinery, but if it is dependent upon power being supplied from the
emergency generator, that generator is to be arranged to start automatically in
case of main power failure so that power for the pump required by 7.4.5 is
immediately available. When the pump is driven by independent internal combustion
machinery, it is to be so situated that a fire in the protected space will not
affect the air supply to the machinery.
Precautions are to be taken to prevent the nozzles from
becoming clogged by impurities in the water or corrosion of the piping, nozzles,
valves, and pump. As an alternative to 7.4.1 to 7.4.7, the arrangement
described in MSC/Circ.668, and amendments thereto contained in MSC/Circ.728
will be accepted or equivalent.
THE BA SET
- Consist of
an air cylinder mounted on a plastic back plate fitted with harness
- A moulded
rubber face mask incorporated demand valve, exhalation valve/speech
transmitter, head harness & visor is connected by high pressure reinforced
hose from the demand valve to the air manifold
- A pressure
gauge & a low pressure warning whistle which give audible warning to the
wearer when 80% of the air has been used and this complete the assembly of the
BA set
- To put into
operation the cylinder valve is opened & the wearer breadth, the demand
valve supplies air according to his requirements at a reduced pressure
irrespective of the work load
CHARGING BA SET
Recharging cylinder to, appropriate pressure as stamped on
cylinder. It is only permissible to fill compressed air cylinder which:
Conform to Notional Standard in force within country of use.
Are stamped with test date and test mark of inspection
authority.
Have not exceeded test interval indicated on cylinder.
Do not show signs of damage or corrosion, which could be a
potential hazard, and that cylinder, is in good condition.
Do not show any signs of moisture (water droplet) in
threaded connection.
Note:
Observe the following, to avoid high, water content of
breathing air in compressed air cylinder:
Compressed air cylinders must not be completely emptied
(depressurize) when used with compressed air respiratory protection equipment.
Maintain above atmospheric pressure after use. If however
cylinder is completely emptied, ensure that cylinder valve is closed.
Cylinder valve outlet should be protected against ingress of
dirt and moisture at all times i.e. after removal from compressed air
respiratory protection equipment, and fit
Protective cap immediately must be protected against impact
and heat when transported.
CAUSES OF OIL OVERFLOW FROM PURIFIER
- Wrong
temperature & viscosity of the oil’
- Density of
the oil not suitable
- Using wrong
gravity disc
- Speed of
the purifier too slow
- Bowl stuck
open
- Loss of oil
seal (faulty or worn ‘O’ rings)
- Insufficient
back pressure
WATERTIGHT BULKHEAD
Function
- Divide ship
into watertight compartment & thus restrict the volume of water, which may
enter the ship if the shell plating damaged.
- Separate
different type of cargo & to divide tanks & machinery spaces from cargo
spaces.
- In the
event of fire, it reduces largely the rate of spread.
- Increase
transverse strength of the ship
- Reduce
vertical deflection when the compartments are full of cargo.
WATERTIGHT DOOR
- It fitted
to any access opening in a watertight bulkhead.
- Openings
must only be cut where necessary for the safe working of the ship.
- Kept as
small as possible, 1.4 m high and 0.75m wide being usual.
- Material
mild steel, cast steel or cast iron.
- Hinged,
vertical, and sliding type of watertight door.
- Hinged type
not permitted below waterline.
- Good
sealing
- To
equivalent strength to unpierced bulkhead .
- Sliding
door may be hand controlled.
- It has an
indicator at above deck operating position showing if they are open or closed.
- There must
be no groove at the bottom door to collect dirt, which prevent door from
closed.
- Must have
rubber packing around the door.
- Solas
requirement stipulated that they be capable of
being operated when ship listed
15°, and be opened and closed from a position above the bulkhead deck or
locally .
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