DieselShip's Online Content Library

Q1. Describe the examination you will carry out on the following parts of Air Compressor,

a) Suction and delivery valves and seats. (4)

b) Relief valves and bursting discs. (4)

c) coolers and cooling passages. (4)

d) Piston and piston rings. (4)

Q5. a) Describe onboard main Air Compressor maintenance schedule. (8)

b) Describe malfunctions observed on Main Air Compressor. (8)

Q9) Write short notes on:

(a) Control air dryer - working principle with diagram, of any one type of dryer of your choice (8)

(b) Any two types of Ballast water treatment system (8)

Q5. Sketch and describe an independent two-stage air compressor. Draw a set of typical indicator diagrams and insert the various pressures and temperatures. Indicate the effect of a leaking HP suction valve and excessive HP clearance volume (16)

Q4. (a) Describe uses of compressed air onboard the ship. (6)

(b) Describe maintenance schedule of various systems on main air compressor. (6)

(c) Describe Isolation procedure of main air compressor before starting any work (4)

Q7. State the causes and remedial actions to be taken in case of the following occurring on an air compressor:

(a) Water mixed in the crankcase oil (4)

(b) LP safety valve blowing (4)

(c) Bursting disc rupture (4)

(d) Problems caused by detective piston rings (4)

Q3. Clean and dry control air is essential for efficient trouble-free operation of a ship’s pneumatic’ control air system.

a) Sketch and describe a low-pressure control air system used on board ships showing various arrangements to deal with dust oil and moisture as well as safety system. (8)

b) Explain using a line diagram, arrangements provided, to reduce the air pressure to 7/8 bars. Required for control air system. (8)

Q9.a) Explain why air receivers should be drained frequently and its internal surfaces to be provided with protective coatings (6)

b) Describe the procedure for internal inspection of air receivers and the possible defects that may be encountered. Suggest suitable repair methods for the defects. (6)

c) Describe fault conditions associated with air receiver mountings and the remedies to rectify the same. (4)

Q6. i) Explain the term ‘Volumetric efficiency’ in respect of air compressors. (3)

ii) State reasons for drop in ‘Volumetric efficiency’ and how same can be restored? (7)

iii) Explain the purpose of ‘unloader’. Name the methods used for unloading, for ‘starting’ and ‘stopping’ when on automatic operation. (6)

Q4. Sketch and describe an Independent two-stage air compressor. Draw a set of typical Indicator diagrams and insert the various pressures and temperatures. Indicate the effect of a leaking H.P. suction valve and excessive H.P. clearance volume. (16)

Q6. Explain why each of the following features is considered desirable for air compressors:

(a) A single-throw crank for a multi-stage compressor; (4)

(b) Minimum clearance volume· (4)

(c) Multi tubular inter-stage cooler; (4)

(d) Generous size of suction filter.  (4)

Q8. i) Explain the basic theory of air compressors using a basic P-V cycle diagram, for a single stage air compressor, showing (a) adiabatic (b) polytropic (c) isothermal lines of compression. (6)

ii) Explain the advantages of multistage compression and intercooling. Superimpose the effects of both on the P-V diagram mentioned above. (6)

iii) Briefly explain bumping clearance. (4)