Q a) For freon-22 vapour compression refrigeration machine, state how each of the following faults are identified & rectified:
i. Air in the system;
ii. Moisture in the system;
iv. Over charge
b) Describe with the help of diagram detailing the device s incorporated into the refrigeration system to protect the machinery & equipment against malfunction.
Q a) Sketch a ship’s indirect refrigeration system arranged for cooling containers showed in stacks in the hold.
b) Describe the refrigeration system sketched in (a)
c) State the advantages of the system described in (a) compared with containers with their own refrigeration self contained units.
Q With respect to refrigeration gases used onboard vessels, answer the following:
a) Explain ozone depleting potential of the conventional refrigerant gases
b) Name the alternate refrigerant gases available & being used onboard.
c) Explain the steps you will take to assure that release of refrigerant gases from the plant is minimized during normal operation & during maintenance activities.
Q With reference to lubrication of reciprocating Freon refrigerating compressor,
a) State with the reason the characteristic of the lubricating oil in use in such a system,
b) Discuss each of the following with respect to cause effect & remedy:
i. Copper plating
ii. Freon cloud point
iii. Freon floc point
c) Sketch a ship’s indirect refrigeration system arranged for cooling containers stowed in stacks in the hold.
Q With reference to main refrigeration plant give a reason for each of the following operational irregularities & state how it is dealt with:
a) Rapid loss of the crankcase lubricating oil in a Vee block machine
b) Gradual fall off in the refrigeration effect over a comparative short period of time
c) Icing up at compressor suction
d) Frequent cutting off of compressor on high pressure.
Q a) Sketch & describe a high pressure cut-out in a refrigeration system.
b) The refrigeration compressor has stopped due to operation of the h.p. cut-out Explain
i. The possible caused.
ii. How these causes would be found and possible remedies.
c) What steps are taken if the compressor “short cycle” on the low pressure cut-out?
Q a) Draw a block diagram for a fully automated accommodation air conditioning unit, labelling the component parts & indicating the directions of air flow..
b) Explain why the unit includes means of the dehumidification & humidification.
c) A chart is used for assuring that the accommodation conditions are within the so called Comfort Zone: what useful information does that chart give?
Q a) Describe an air conditioning system for a passenger car ferry.
b) Explain in detail how the humidity of the air is measured & controlled.
Q a) Sketch & describe the purpose of an expansion fitted in a refrigeration system;
b) With regards to high pressure cut-out in a refrigerator, state 4 operational circumstances that may cause a high pressure operate.
Q With reference to air conditioning units:
a) With the help of a sketch, explain the operation of a unit which includes means of dehumidifying, humidifying & refrigerated cooling.
b) Describe the conditions that could lead to legionnaire’s growth.
c) List the precautions necessary in the maintenance of air conditioning systems to decrease the risk of legionnaire’s disease being contacted.
Q a) Describe the procedure to be adopted for the inspection of a safety valve fitted to an exhaust gas boiler stating, with reasons, which parts should receive particularly close attention.
b) Describe the procedure for the setting of safety valves of the exhaust gas fired auxiliary boilers.
c) Explain the precautions a 2/E should take after setting of safety valves as in (b).
Q Sketch a high lift safety valve lid and seat detailing their special features. Describe how such a valve is overhauled & any clearance that should be measured & noted.
Q Describe how you, as 2/E, would prepare an auxiliary boiler for survey by a Classification Society.
Q a) State the standing instruction you, as Second Engineer, would issue with respect to the action to be taken in the event of the boiler uptake fire.
b) State how the incidence of the uptake fires may be minimized
c) State the reasons for the blow -back from the furnace of an auxiliary boiler.
d) State the standing instruction you, as 2/E would issue with respect to the avoidance of boiler furnace blow- back.
Q Discuss, with reference to the super heater outlet temperature of a main boiler operating at a constant load, the following statements:
a) An increase in excess of the air will tend to cause a decrease in super heater outlet temperature due to the cooling effect of more air being introduced.
b) A decrease in economizer inlet temperature will tend to cause a decrease in super heater outlet temperature due to the cooling effect of the more water being introduced.
c) Badly fouled generating tube banks will cause an increase in the super heater outlet temperature.
d) Excessive amounts of the total dissolved solids in the boiler water will cause variations in the super heater outlet temperature.
Q With reference to feed water regulation:
a) Describe, with the help of sketches, the operation of a boiler feed water regulator controlled by at least two other parameters besides water level in the drum
b) Give reasons for the inclusion of the other elements besides water level in the controlling feed flow.
c) Deduce the possible effects on the system when the drain valve in the constant leg in the level transmitter starts to the leak.
Q a) Discuss the possible reasons for the following changes in boiler water test results, at state what actions should be taken in the each case:
i. Reduction in total dissolved solids & chemical reserves.
ii. Reduction in phosphate reserve, with increase in chlorides & total dissolved solids.
iii. Reduction in the alkalinity reserve only.
iv. Increase in the oxygen levels only.
b) State why the complete results of boiler water tests are logged or entered into a data retrieval system rather than a note being made of any particular result which may be outside the set limits.
Q Describe how the following conditions can be avoided in auxiliary boilers:
a) Feed contamination by the oil heating coil drains
b) Internal corrosion
c) Furnace blowback
d) Uptake fire
e) Furnace distortion
f) Difficulty in maintaining normal water level
Q An auxiliary boiler water level control system has a differential pressure transmitter as the detecting element for water level:
a) Sketch & describe such an arrangement
b) If the transmitter was damaged describe how a replacement unit would be calibrated.
Q Describe how the following conditions can be avoided in auxiliary boilers:
a) Furnace distortion
b) Uptake fires
c) Difficulty in maintaining normal water level
Q Sketch & describe a boiler water level controller of the float operated type. State the reasons for having this mechanism on the boiler & using the controller and boiler for analogy explain the following terms:
a) Detecting element
b) Servo motor
c) Desired value
Q With reference to auxiliary boiler safety valves:
a) Describe, with the help of a sketch, the safety valves for an auxiliary boiler.
b) Identify, with the reasons, the parts that require particularly close attention during overhaul.
c) Describe how the safety valves are reset after an overhaul, assuring no feathering.
Q a) Describe with the aid of sketch the operation of Boiler feed water regulator controlled by at least 2 other parameter beside water level in the drum.
b) Give reason for the inclusion of the other element beside water level in the controlling feed flow.
c) Describe the possible effect when the drain valve on the constant head leg in the level. transmitter starts to leak.
Q Describe how you as C/E would prepare an aux boiler for a class survey.
Q Give possible reasons for the following in boiler water test result and state what action should be taken:
a) When total dissolved solids and chemical reserves are reducing.
b) When phosphate reserve is reducing but chlorinate and TDS are increasing.
c) When alkalinity reserve is only reducing.
d) When oxygen level only is increasing.
Q With reference to main boiler super heater arrangements:
a) Compare the advantages and disadvantages of contra flow with parallel flow design
b) Describe how the element tube banks are supported yet allow for expansion
c) Describe how boiler carryover affects super heater effectiveness and condition
Q With regard to the safety valves fitted to a boiler.
a) i. State why an easing gear is fitted.
ii. Discuss the conditions under which easing gear may be used.
iii. State any precautions that may have to be taken during the use of easing gear.
b) Explain why corrosion occurs in wet steam lines and in condensate system.
Q A fire in the exhaust gas boiler on a motor ship may develop in two or three stages. With reference to such situations, discuss:
a) The factors which could be a cause for initiation and development of:
i. Ignition of soot
ii. Small soot fires
iii. High temperature fires
b) State the standing instructions you, as a Second Engineer Officer, would issue with respect to the action to be taken in the event of a boiler uptake fire.
Q Sketch and describe a suitable burner which can be used on Gas and Oil in a boiler of a LNG ship. Enumerate the normal attention required on such burners?
Q With regards to keeping the gas side of a boiler in good condition discuss each of the following:
a) The mechanism of combustion stating the factors which are important for good combustion
b) Oil fuel treatment
c) Soot removal equipment
Q Explain why regular testing of water in the auxiliary boilers is advisable.
State what actions are required when measure values appreciably differ from desired values in each test. Give an interpretation of the situation when both alkalinity and chlorinity are found to have changed considerably.
Q a) Draw line diagram of a feed water system for an auxiliary boiler, labelling all the principal items and showing the direction of flow.
b) Explain how feed supply to the boiler is regulated? Explain rising water level characteristics of level control.
c) State what preventive and corrective measures may be taken if oil contamination of the feed water takes place?
d) State what means are provided to prevent oil contamination of the feed water.
Q a) Describe how you would test boiler water for:
b) State the values obtained from the tests that would be considered suitable for a water tube boiler if the test results were unsatisfactory, what remedial action would you take?