DieselShip's Online Content Library

Q1. In a marine boiler water level control system, Proportional plus Integral (P+I) control is widely used instead of simple Proportional (P) control. What is the primary operational reason for adding the Integral action? (16)

A) To eliminate steady-state offset caused by changes in steam demand.

B) To instantly increase the response speed to sudden load changes.

C) To decrease the maximum overshoot of the water level.

D) To prevent the control valve from experiencing mechanical wear.

Briefly justify your answer.

Q2. a) Sketch a line diagram showing a typical 'Inert Gas System' used for inerting the cargo tanks of oil tankers, labelling the components parts. (6)

b) Describe the system. (8)

c) State what oxygen content you would expect in the flue gases if good combustion is achieved (2)

Q3. Which of the materials listed is used as the dynamic seal material on mechanical seals installed on most centrifugal pumps used in water service? (16)

(a) Copper.

(b) Copper and carbon.

(c) Carbon.

(d) Bronze.

Briefly justify your answer.

Q4. With reference to a typical shipboard refrigeration system:

a) Sketch the arrangement which controls superheat temperature of refrigerant gas leaving the evaporator. (8)

b) Describe the operation of the arrangement sketched in (a) assuming one of the HFC refrigerants is the working medium. (4)

c) Explain the purpose of the equalizing connection. (4)

Q5. With regard to keeping the gas side of boilers in good condition,

Discuss EACH of the following.

1. The mechanism of combustion, stating the factors which are important to good combustion (6)

2. Oil fuel treatments (5)

3. Soot removal equipment (5)

Q6. Explain why regular testing of water in auxiliary boilers is desirable. For each, test normally carried out, state - (8)

a) Reasons for making the test

b) Acceptable values for any particular type of auxiliary boiler (4)

c) Action required when measured values differ appreciably from desired values. (4)

Q7. With reference to electric arc welding:

a) Draw a labeled sectional sketch of a satisfactory butt weld. (6)

b) Briefly define the following defects that may occur and how they may have been caused (6)

i) Under cut

ii) Splatter

iii) Inclusion

iv) Blow hole

v) Incomplete root penetration

vi) Lack of fusion

c) Why is alternating current generally more popular then direct current for metal arc welding? (4)

Q8. Compare the desirable qualities of the lubricating oil selected for each of the following duties and give reasons for the differing properties of the oils recommended for these three purposes. (16)

a) Auxiliary diesel engines

b) Stern tube bearings

c) Refrigeration compressors

Q9. Reverse osmosis is the contemporary alternative for shipboard production of drinking

a) Describe using simple diagrams where necessary, the principle of:- (6)

i) Osmosis.

ii) Reverse osmosis.

b) Sketch a line diagram showing a ‘single pass system’ for producing fresh from seawater. (4)

i) Describe such a system. (4)

ii) State the safety features that may be incorporated into the plant. (2)