Causes for main engine failure

Trunk engine piston seizure:
Causes:
1. Blocked coolant supply to piston.
2. Overheating of the unit.
3. Exhaust valve damaged.
4. Rings damaged.

Burning away of piston crown:
Causes:
1. Piston’s inside cooling gallery, fouled with deposits.
2. Incorrect spray angle of fuel valve.
3. Injection viscosity too high.
4. Fuel containing excess amount of water. [Maintain separation temperature 98°C and minimum throughput.]

Corrosion of crank pin:
Causes:
1. L.O. contaminated with SW or FW, due to leakage. [ When combustion products, SO₂, enter crankcase, through blow pass ( trunk type) or defective diaphragm (crosshead type), they react with water and form H₂SO₄ and attack crankshaft.]
2. By galvanic action, when crankcase LO is contaminated with SW.
3. Faulty purification system cause LO contaminated with FW.
4. Piston cooling system, leaking into crankcase.

White metal bearing failure:
Causes:
1. Edge carrying wear [Due to out of true of bearing bore, or deviation from journal geometry]
2. Striations wear [Striation and embedding of foreign particles on running surfaces.]
3. Overheating of layer [Due to lack of lubrication and contamination of LO.]
4. Erosion wears [Some abrasive particles carried along with LO.]
5. Electro erosion [If crankshaft is inadequately grounded.]
6. Corrosion [Contamination of LO with SW.]

Broken piston ring:
Causes:
1. Insufficient ring and groove clearance [Vertical clearance: 0.4 mm for top ring: 0.2 mm for lower rings.]
2. Insufficient ring gap. [Butt clearance: 0.5% of cylinder bore, for moderate rating and 1.0% for higher rating. Over 500 mm bore.]
3. Excessive liner wears.
4. Excessive relieving at ring edge. [Oil wedge action cannot be attained.]
5. Insufficient lubrication.
6. Excessive lubrication. [Excessive ring zone deposits and fouling of grooves and micro-seizure may occur.]
7. Improper ring material.
8. Misalignment of piston.
9. Improper fitting.
10. After burning.

fuel valve defects

Fuel Valve:

Injector: Requirements:

1. Spray must be in atomized state, at all times, regardless of engine speed.
2. Pressure should be set at required value. [Too high – late injection: Too low – early injection].
3. Valve seat should not pass more than stated quantity of fuel, when testing, for a given period of time.
4. Valve lift should not be excessive. [Excessive valve lift can cause hammer action to valve seat, leading to permanent damage.]
5. There should be sufficient leak-off for lubrication.
6. Should be snap-seated and no dribbling.

Excessive Atomisation:
1. Smaller oil particles have insufficient KE, to go through combustion chamber.
2. Dense compressed air has high resistance to the motion of oil particles.
3. Smaller particles tend to cluster around injector tip, and oxygen-starved during combustion.
4. Can cause after-burning.

Insufficient Atomisation:
1. Oil particles become larger and will have more KE and travel further into combustion chamber, and some may rest on cylinder liner and piston crown.
2. Carbon built-up around the top of cylinder and piston crown.
3. Lower rate of combustion and after burning.

Low Penetration:
1. Less intimate mixing of air and fuel particles in combustion chamber.
2. Fuel cluster around injector tip causing after burning.

High Penetration:
1. Fuel particles travel further into the combustion chamber and some may rest on the cylinder liner and piston crown.
2. Lower rate of combustion and after burning.

Needle Scores:
Causes:
1. Due to excessive valve lift. Normal valve lift is about 1.00mm.
2. Cat-fines carried over from purifier and filters can cause abrasion, and needle scores.

Effects:
1. Due to needle score, fuel leakage across the seat will occur during the cut-off period. (Originally, the angle of needle valve and its seat is cut in difference of about
1°~ 2° to achieve point contact, thus preventing dribbling.)
2. Carbon formation at nozzle tip interferes the spray pattern causing poor combustion, high exhaust temperature, and increased fuel consumption.
3. In excessive case, surface burning of piston crown, too much carbon deposits in combustion space will occur.

Leak-off of a fuel valve:

1. Amount of fuel oil, which seep past the needle valve and nozzle body and it is used for lubrication.
2. Little Leak- off may seize needle in nozzle body.
3. Too high Leak-off reduce quantity of atomized fuel into combustion chamber.

Shell Defects

Shell Plating

At the renewal of the cracked or wearied out plates, it is necessary to see the "Shell Expansion Plan" . Because there are many kind of steel plate such as mild steel plate, high-tensile steel plate etc. Among them there are many kind of steel such as A-grade, B-grade,　C-grade etc. When renew the shell plate, the same steel should be used.

Typical defects found in the bottom and the side shell are as follows.
8.1 Bottom Shell 
(1) Bottom scratches and Dents 
Most damage to the bottom shell is due to contact with objects on the seabed. Bottom scratches are slight damages. Such damage happens when the ship operates in shallow waters such as the Mississippi river, near the coastline, etc. In many instances, bottom damage due to contact starts from the forward part and disappears around midship.
Because of scratches, the bottom paint has peeled off and corrosion occurs. In this case, remaining paint and rust should be cleaned by shot blasting and properly re-painted . When the bottom has had contact with a coral reef or rocky seabed, large dents and/or holes appear with scratches. In this case, as a matter of fact, fractured shell plate should be cropped and renewed with damaged internal members. If the dents are relatively small, they may be left as they are with some effective internal reinforcement.
If we find a large fractured opening during the bottom inspection, naturally we should recommend repairs. However, there have been many instances where the shipowner has believed that there were no abnormalities and dents were found during the bottom inspection, which naturally gives the shipowner a headache. The shipowner usually decided sailing schedule beforehand, they hate prolonging docking period because of major repairs, they persists in putting off major repairs, and try to carry out simple repairs within the drydocking period. That is why sparks usually fly between the Surveyor and the shipowner's representative.
Regardless of experience of bottom inspection, the surveyor always feels uneasy before docking survey.


Fig.8-1 Damage in bottom shell

(2) Dents due to panting 
When the ship sails in rough weather without reducing speed, dents might occur in the keel and A strake starting from the fore peak tank to the middle part of No.1 Water Ballast Tank , because of the relation between ship speed and curvature of the forward bottom. In the worst case, the floors in the tank and bottom stiffeners buckled.
Naturally, the Surveyor should recommend repairs to the shell, as well as the internal members.

(3) Corrosion of keel and adjusent A strake
Re-painting of the area on the keel block is impossible. So after undocking and also long voyage, these unpainted area is much more corrosive than painted area. the corrosion of welded beads is more heavy than the plate itself.
At the bottom survey previous un-painted area which we can find easily because of much rust should be carefully examined especially welded beads. When the beads is excessively corroded, rust should be removed and it is necessary to re- weld and after well painted.
(4) Corrosion of beads 
Grooved corrosion, which at first glance looks like cracking often occurs in heat affected zones of seam and butt weld. It means the both side of beads. The corroded beads should be gouged and re-welded.
(5) Wrinkled corrosion
Small craft and ships adopting the transverse system of framing might develop wrinkles in the transverse direction in the mid-ship area of the bottom shell. These wrinkles are considered to occur because of buckling. If possible, it is better to fit the transverse carlings in the double bottom tank to prevent buckling.
(6) Sea chest 
After removing the grating of the sea chest in way of the engine room or the pump room, climb onto the staging and inspect the internal parts of the sea chest. The sea chest forms a discontinuity with the rest of the bottom shell; therefore, cracks might appears at fillet welds of girders and floor plates.



Fig.8-2 Cracks in Sea Chest


Photo 8.1 Corrosion of Keel and A strake in way of forward bottom


Photo. 8.2 　Ship with False Keel
When the ship with a fales keelis seated on the ordinary keel blocks, fales keel and center girder may be heavily damaged.
i
Photo. 8-3　Big damage in bottom (1)
Ballast water comes out from the double bottom tank.
　　

Photo 8-4 Big damage in bottom (2)
Big damage can be detected by anybody


Photo 8-5 Slight Dent
A slight dent in a curved plate is difficult to detect


Photo 8-6 Corrosion of welded Bead (1)
Corrosion in a welded bead of a bottom shell plate looks like a crack, but is not a crack. As shown in the macro etching, this corrosion appears in a heat-affected zone.

Photo 8.7 Corrosion of Beads (2) Macro Etching



Photo 8-8 Reed Screen Bottom Plate Corrosion
Stress corrosion due to buckling in the midship region of the bottom plate in a transversely- framed construction; the dent itself is small. Reinforcement by fitting a carling inside the tank is recommended.

9.2 Bilge Keel 
In large tankers with the midship coefficient approaching 1.0, the bilge keel may not be fitted when the ship is newly built. If bilge keels have not been provided on both sides during the bottom inspection, check whether the ship had no bilge keels when the ship was constructed or whether they have been ripped off during a marine casualty. If there are traces of welded beads on the bilge strake, we may conclude that the bilge keels have been ripped off during a marine casualty.
Damage to the bilge keel is as follows;
(1) Bilge keel dropped off, a part of bilge keel ripped off, kinks in bilge keel
The bilge keel is a member that does not need to conform to classification society rules. However, if it is damaged, it is normal to repair the bilge keel, usually under insurance.

(2) Cracks at ends
Aged ships which constructed with rivet not weld. Rivets at the ends of the bilge keels often worked loose. In a welded ship, the welds at the both ends are provided with large leg lengths, but sometimes cracks are found at the ends.

(3) Local joints of the bilge keel
The block butt in the hull becomes a local joint in the bilge keel. If welding at this location is defective, cracks appear in the joint. If the crack progresses and reaches the bilge strake, water penetrates into the hull. In case of tankers, this defect leads to marine pollution. During a bottom survey, check the side shell plates at the location of the bilge keel　join.

(4) Box-type bilge keel
In fine and high speed ships, box-type bilge keels are frequently used. The box structure is watertight, but water sometimes penetrates into the box through small cracks in the welds of local joints. If the local joint is wet, there is a possibility that water has penetrated into the box. In such cases, carry out the air test, find locations where leaks start and recommend welding repairs.

(5) Corrosion of the bilge strake
Although not directly related to the bilge keel, when we inspect the bilge keel, check for corrosion of the bilge strake above it. Bige strake above the bilge keel
is corrosive than other strake.


Photo 8-9 Deformation　of bilge keel


Photo 8.10 Corrosion of the Bilge Strake above the bilge keel

The bilge keel is not directly welded to the shell; it is generally connected to the shell through a flat bar. If it is welded directly to the shell, there is a strong possibility that cracks might develop in the bilge strake when the bilge keel suffers damage.

Fig. 8-3 Example of Bilge Keel


Fig. 8-4 Crack at Bilge Keel End (1)


Fig. 8.5 Crack at Bilge Keel End and joint of bilge keel
Cracks tat the joints of the bilge keel might develop, causing cracks in the bilge strake.


Fig. 8-6 Example of Box-type Bilge Keel

8.3 Side shellThe followings are the example of the defects in the side shell.
1) Corrosion
2) Dents and fracture due to contact with quays or floating objects
3) Cracks in the longitudinal or transverse direction as a result of development of cracks in the internal members
4) Wear to the shell due to internal corrosion in addition to the above defects
5) Cracks might occur in the side shell due to shearing force　caused by inappropriate jumping loads. however, no cases of damage to a side shell due to shear caused by loads in the longitudinal direction have been reported.

Fig. 8-7 Corrosion of the side shell

Fig. 8.8 Damage due to Contact
Number in the circle corresponds to the followings

The side shell at the bow and the stern is thinner than the shell in midship part. That is why corrosion of the side shell progresses in the region between the fore peak tank and the end of No. 1 hold, and between the aft peak tank and the engine room. In aged ships the fracture openings spears in way of the engine room. When the shell plate has the excessive rust, the plate thickness should be measured.

(2) Dents and fracture due to contact

1) Both forward and aft ends of flat parts
Dents and fractured openings are likely to appear in these parts when the ship comes into contact with the quay when berthing. These defects are often observed in car carriersand ships operating in narrow waterways, such as the St. Lawrence waterway are also observed to have dents at these area.

2) Fore and aft body near the waterline
Dents appear in these area when the ship is pushed by a powerful tug boat while berthing.

3) Stern
Deformation appears at the stem when the ship hits floating objects. Sometimes it is difficult to find such a deformation just looking from side. It is better to examine from just in front of the ship.
Indent of the shell is difficult to distinguish so sometimes it is better to examine　from the deck looking downwards .

4) Near the bell-mouth
Dents and fractured openings are caused when the anchor fluke frequently hits the side shell.

5) Range of abrasion by chain
Grooved corrosion due to chafing by chain appears in this area. cf 8-(2)-2

6) Near the hatch openings
In ships that load/unload cargo from/to barges, dents are often caused when the barge or the cargo comes into contact with the ship.

7) Propeller and rudder
The propeller and rudder might hit floating objects, get fouled in fishing nets, propeller blades might be bent, guard ring might fall off, and the portable box for the rudder sometimes drops off.
8) Bilge keel
Instances have been reported of a part of or the entire bilge keel dropping off after a ship hit a floating object. The damage of the bilge keel have been observed frequently. Carefully check the deformation of bilge keel looking through　from fore end to aft end.

(3) Cracks
Cracks in the shell plate mostly develop from cracks of the internal members and they spread to the shell plate. Cracks might occur in the transverse or longitudinal direction; some cracks appears in the shape of a star.

1) Aft end of collision bulkhead
A large number of internal members, such as frames and stringers, are provided in a relatively small area of the fore peak tank. It means that the fore peak tank is a rigid construction collision. While the hold adjacent to the fore peak tank is a large, broad space with a small numbers of internal members per unit volume. Moreover, this region is often subject to large wave impacts, which cause cracks in No. 1 hold.
As the reinforcement against panting, classification rules request side stringers or brackets in the region between the collision bulkhead and 0.15L from the bow. But at the end of these members crack appears and develop to the side shell. Therefore, the vicinity of the ends of these members should be carefully inspected . Initial cracks appear in the vertical direction and have a length of 50 mm to 100 mm.



Fig.8-9 Extension of internal crack to shell plate (1)



Fig. 8-10 Extension of internal cracks to shell plate (2)

Fig.8-11 Crack near the bulkhead

3) Bilge keel See Section 9.2. 

4) ,(5) Cracks in the sheer strake at the ends of superstructures 
Cracks sometimes appear at the sheer strake at the fore and aft ends of the superstructure (Bridge) of "Three Islander" ship and long Poop or long F'cle ships because of hogging and sagging.
Sheer strake at the break of the superstructure should be carefully examined

Fig.8.12 Crack at the sheer strake.

(6) Shell plate in way of the the aft peak tank
In ships with a long aft peak tank such as ocean tugs boats or some car carriers, aft peak above the rudder is flat and wide. sometimes crack because of stern vibration appears in the APT and may propagate to shell plate. Care should be taken.

(7) Bilge part
Cracks at the lower ends of frames in cargo holds sometimes extend to the shell plate. Cracks in the shell plate appear in the horizontal direction
.
(8) Vicinity of bulkheads
Cracks may also occur in the vertical direction along the bulkhead due to the difference in rigidity of the frame and the bulkhead. these cracks propagete to　shell plate. This situation is shown in the figures below. Shell plate In the vicinity of bulkhead should be carefully examined not only outside but in the hold side.
especially in aged ships
(9) Crack in rudder plate ; Please refer to the Rudder section.

4) Corrosion 
The shell plate is generally painted when the ship is in drydock but in the hold it is not well painted. In the following area shell plate is thinner than other area. If necessary the thickness should be measured in aged ships. Locations to be checked carefully are shown in the figure below.

Fig.8-13 Corrosion from inside
Number in the circle corresponds the followings.
.
(1) Chain locker bottom
Ventilation of the chain locker is not enough and bilge water accumulates in the bottom, resulting in the rapid onset of corrosion. In large ships, the chain locker is isolated from the shell plate, corrosion does not appear in the shell plate. However, in hte normal ships, the shell plate forms a part of the chain locker, side shell plate corresponding to chain locker bottom soul be carefully examined.

Fig. 8-14 Chain locker bottom

(2) Tank top
Corrosion at the sides of the tank top plate proceeds faster than other area, but it is not faster than in chain locker. If corrosion at the sides of the tank top plate in the aged ships is neglected, it extends to the shell plate and sometimes it leads to corroded openings appear in the shell plate. In ships where the sides are raised, such as bulk carriers, this problem does not occur.
(3) Aft end of 'tween deck 
In ships with a 'tween deck, bilge water generally accumulates at the aft end of the deck and causes corrosion that extends to the shell plate. This is not a major problem, except in aged ships.
(4) Near the forecastle aft bulkhead
Bilge water in the forecastle accumulates at the aft end on both side. Therefore, forecastle end wall on both lowest corners to be carefully examined .
(5) Corrosion below side scuttles
Starting with Special Survey No. 2, it is mandatory to measure the thickness of the shell plate below side scuttles. Rules prescribe inspections of the condition of the shell plate below side scuttles after removing the lining during Special Survey No. 3. In practice, the space below the side scuttle is narrow and is covered with lining boards. Sea water often enters through open side scuttles; the humidity is so high, and corroded fracture openings gradually appear in the shell plate. Because this area is above the waterline, we need not be excessively concerned about the danger of water flooding into the ship immediately. However, in the past, the "Umegaka Maru" owned by NK capsized because of water flooding the ship through side scuttles;
therefore, when we entering the dock, check the plate below the scuttles on the super-structure from the dock floor or dock sides and compare the condition with the surrounding shell plate. If rusting is excessive, enter the cabin after completion of the bottom inspection and ask to remove the lining and examine the state of corrosion in the superstructure side plate.

Ref. The Classification Rules In the Special Survey N0.3 request as follows : "The lining in way of the side scuttles is to be removed as required by the surveyor, and the shell plating should be examined."

Fig.8-15 Pay attention to the area below the side scuttles

Photo 9.11
Attention to the lower area of side scuttle

(6) Forward and aft of bulkheads See (8) 
(7) Upper edge of bilge strakeSee 5) of Section 9.2 for external corrosion
of the bilge strake

Refrigeration system faults, causes and remedy ?

Effect of Sea Water Temperature:

              For good heat transference, a temperature differential of 8oC between cooling water inlet
and the condensing temperature is used. Under cooling, which is advantageous, under
standard condition, will be 5 oC. Therefore any changes of the sea water temperature will
affect the degree of under cooling.

When sea water temperature increases :

• The degree of sub cooling is reduced.
•  Increases the flash off percentage, efficiency of plant drops.
• The condensing pressure will be higher.
•  Superheat increases discharge temperature may be too high, compressor.
• overheated

When sea water temperature decreases :

• Very low or no super-heat, liquid may be drawn into the compressor, causing damage to it
• Less flashing off of the gas at the expansion valve

Air in the system:

                Air is admitted in the refrigerant system during repairs, or can leak into the low pressure
side, when the plant is running with evaporator pressure below atmospheric. This air
is pumped around the system as far as the condenser, where it is accumulated, as it
cannot be condensed.
The symptom, which indicates air in the system, is a steadily increasing reading on
the condenser pressure gauge the accumulation of air reduces the effective area of
condenser available for condensing refrigerant. The efficiency of the plant is reduced.

Checks:
               If air leakage is suspected, it can be checked by stopping the compressor, closing the
condenser outlet liquid valve with the condenser sea water still circulating. After a few
hours, equilibrium is reached in the condenser and the condenser thermometer should
read exactly the same on sea water temperature, if no air is present. If the thermometer
reading is higher, then air is present.

Action:
                Air can be released from the system, by crack opening the purge valve on top of the
condenser, or if no valve is fitted, by slacking a pipe connection on top of the condenser.
Dirty condenser or insufficient cooling water
Dirty condenser or insufficient cooling water is indicated by compressor high discharge
pressure and the effect of the poor cooling will be that the refrigerant will not be efficiently
liquefied and the condenser ends and pipes will feel hot.
The cooling water can be restricted due to:

• Choked condenser tubes
• Choked cooling water pump strainers
• Choking of the cooling water system
• The cooling water pump fault

Moisture in the system:

                   Water circulating with the refrigerant, tends to freeze on the thermostatic expansion
valve, causing a build up of pressure on the condenser side and drop in pressure on the
evaporator side due to the blockage. The plant tends to be stopped by the high pressure
safety cut-out.

Remedy:
                    Driers are used to remove moisture, and icing of the expansion valve would indicate
that the chemical is no longer effectively removing the moisture. The chemical, either
activated alumina or silica gel is renewed and the compressor restarted after the ice has
melted. Usually the ice in the expansion valve will melt due to the ambient temperature.

Undercharge :
                    Symptoms of undercharge are a low compressor discharge pressure, lack of frost on
suction pipe, lengthy running times and large bubbles in the liquid line sight glass.
The compressor will tend to become very hot. The result of undercharge is that the
performance falls off.

Check:
                     A leak test should then be carried out over the system to determine the fault and enable
its rectification.
The quickest, but least efficient, test is to examine for traces of oil; wherever oil is
weeping, refrigerant is also being lost. Attention should be concentrated on compressor
glands, flanges and pipe joints, particularly the flared ends of copper pipes.

Following are some of the methods used to detect leak:

•  Leak detector lamp
•  Soap solution
•  Electronic beeper

                    A leak detector lamp for Freon refrigerants may be of the methylated spirit type, but
more commonly uses gas (butane / propane).
The lamp has a pale blue or colorless flame which turns to green, when Freon is drawn
into it by a sampling tube. The open end of the tube is held close to joints and other
potential leakage points around the pipe-work.
The limitations of this type is that a large leak will cause the flame to burn violet and it is
sometimes necessary to ventilate the space to clear excess gas before the leak can be
pinpointed. This lamp can not be used for Freon- free refrigerants.
A soap solution is also used to detect the escaping refrigerant by brushing soapy water
over the joints and flanges. The leak is magnified in the form a soap bubble.
Electronic beeper is used to detect leaks in a Freon- free refrigerant system. This
instrument will sound a beep, in the presence of Freon- free refrigerant.

Charging refrigerant :
                    When charging refrigerant, the refrigerant storage bottle is connected to the charging
valve on the regulator outlet, loosely. The bottle valve is crack open to clear air from
the connecting pipe and the nut is tightened on the nipple of the charging valve. The
charging connection is made to the liquid stop valve or suction stop valve if there is no
valve after the regulator. The bottle must be kept upright to prevent entry of liquid when
the connection is made to the suction side of the system.
On some refrigerant storage bottle, separate valves are provided for liquid and vapour.
The charging valve is opened to one turn off the back seat and with the compressor
running; the bottle valve is fully opened. Charging is continued until the bubbles appear
from the sight glass or the suction and discharge pressures of compressor are normal.
Charging will correct the pressure gauge readings (i.e. condenser gauge about 7oC
below the evaporator on the equivalent saturation temperatures for the pressures).

Overcharge:
                   Overcharge only happens when the system has been charged. It is indicated by the
compressor high discharge pressure and condenser sight glass indicating full liquid.
There are other faults which will result in compressor high discharge pressures. These
include poor cooling, having air in the system and icing of the thermostatic expansion
valve. Such faults occur spontaneously.

Remedy:
                   The charge is pumped to the condenser and the excess refrigerant is released to
atmosphere through a pipe connected up for this purpose.
Oil on cooling coils
Heat transfer would be reduced by oil deposits in condensers and evaporators.
Oil carry over is cut down by the oil separators fitted on some compressor discharge
side. Oil deposit is removed by chemical cleaning as described in the heat exchanger.

Frost:
                   Frost on the evaporator coils reduces the efficiency of the plant by acting as an insulator
between the evaporator and the air in a direct expansion system. The air flow is also
restricted by the blockage, by the formation of ice. Automatic defrosting is carried out by electrical heating, keeps the coils free of ice but
failure of the defrost arrangement allows excessive icing.
Ice on the evaporator can be manually removed by washing it off with a hot water.
Choked expansion valve/moisture in system:
                    A blockage in the system may be caused by moisture forming ice or dirt in the
thermostatic expansion valve, but it can be due to blocked strainers, closed valves or
solenoids which have failed to open.
This is manifested in suction pressure drop and a rise in discharge pressure of the
compressor.

Remedy:
                  The drier should be examined and the drying chemicals will probably need replacement.
Strainers and solenoids needs to be inspected.

Short cycling:
                  “Short cycling” is the term used to describe a compressor unit repeatedly running for
a few seconds and then cutting-out. This is the result of operation of the low pressure
controller. The control is arranged to operate when suction pressure drops, to stop the
machine. It restarts it when the suction pressure rises. Thus any condition which varies
suction pressure over this range will cause the compressor to cut-in and cut-out.

Cause:
                   If a solenoid is opened in the normal way by high cold room temperature, the refrigerant
in passing through will build up suction pressure and the compressor will be started. If
the supply is restricted and insufficient for compressor demand, the suction pressure will
drop and the low pressure controller will stop the machine. The thermostatic valve may
be the restricting device, due to low superheat of the gas leaving the evaporator (from
the insulating effect of ice on the coils) it will be closed in to reduce the refrigerant flow.
Electrical faults
                 These are responsible for a large number of refrigerator problems. Ship vibration, in
turn, is the reason for many of the electrical faults. Loose connections and broken wires
and earths, resulting from chafed insulation, are examples.

Safety Procedures:
Plants are protected by:

• High pressure cut outs
• Low pressure cut outs
• Oil failure cut outs
• Safety valves or bursting discs.

High pressure cut outs are usually set to the pressure corresponding to 49oC i.e. about
5oC above highest expected condenser gauge.
Low pressure cut outs should be set about 5oC below the lowest expected evaporation
gauge reading.
Oil failure cut outs are differential pressure devices as crankcase pressure is not
atmospheric and oil pressure is determined relative to crankcase pressure.
Safety valves are used to protect the condensers against excessive pressures.

Reasons For Turbocharger Damage

Diesel Engine Exhaust Turbocharger Failure 

Turbochargers are among the foremost technologically advanced engine element aboard ship. impeller blades of a medium sized turbocharger often rotate at the maximum amount as 400 revolutions per second. The outer edges of the rotor blades therefore move at 1.5 times the speed of sound.

In the method, the turbocharger digests contaminated exhaust gases of up to 700 degrees centigrade. Thus, the turbocharger may be a terribly sensitive piece of high-speed machinery incessantly serving in harsh conditions and underneath extreme strain. Being on the receiving end of gas flows, turbocharger damages are typically caused by the failure of varied upstream elements.

(1) Diesel engine inlet pressure to reduce main reasons:

(a) the compressor of the filter contamination.

(b) the impeller and vanes diffuser contamination.

(c) the supercharger turbo memory have more carbon deposit, spin resistance increase.

(d) the inter-cooler contamination, increased intake resistance.

(e) turbine exhaust not clear, this is because the pipe blockage, deformation caused by rotor speed rise is  not high.

(f)supercharger outlet pressure drop suddenly, it is because of bearing damage caused by.

(2) Compressor surge main reasons:

(a) diesel engine emergency cut-off or sudden unloading (urgent throttle back).

(b) the atmospheric temperature changes cause surge. In the summer of the supercharger with test, in winter could happen surge, this is because the temperature change make working point change and cause.

(c) compressor contamination, especially vanes diffuser contamination.

(d) a engine plant 2 sets of supercharger, Shared a piece of inlet manifold, when a cylinder does not work, can lead compressor surge.

(3) Diesel engine inlet pressure is too high. Generally speaking, the inlet pressure is too high in the supercharger itself is not the problem, but by the engine of the cause, the main reasons are:

(a) the vent valve leakage.

(b) because of engine fuel injection timing inappropriate or other causes for combustion period is too long, to drive a turbine heat increase, speed up, inlet pressure increase.

(4) Produce continuous abnormal sound: this kind of failure is due to the majority of rotor and shell as a result of the collision. Due to the rotor and shell assembly clearance is small, if installation misadjustment or bearing serious damage, then hitting.

(5) The lubricating oil temperature is too high (above 105 ℃) of the main reasons:

(a) the turbine oil, gas seal damage, high temperature gas into the oil chamber.

(b) the bearing damage.

(6) Oil leakage: compressor seal close to the edge of the impeller is low pressure area, easy to produce the oil leakage fault. Main reasons are:

(a) the lubricating oil return not free. The reason has return line congestion, return line sectional area is too small, pipe joint gasket inner hole diameter less than return line; Diesel engine in the crankcase oil level higher than standard, cause oil return difficult; Diesel engine crankcase ventilation blocking or cylinder seal bad, gas expell, make the crankcase internal pressure rise.

(b) the compressor end O ring damage or material ageing and lose sealing effect.

(c) turbocharger oil inlet pressure is too high. Normal pressure is 0.25 ~ 0400000 mpa, if pressure is higher than 0.6 million mpa, from exhaust muffler nozzle will find from the supercharger turbo end leakage oil.

(d) ring not installed correctly or damage.