DieselShip's Online Content Library

Q1. a) What is intrinsic electric safety? Discuss the specific maintenance protocols, inspections, and safety measures required to ensure the reliability and safety of such equipment on board ship. (8)

b) Describe intrinsically safe equipment used on board ship. (8)

Q2. a) Explain why it is necessary to have reverse power protection for alternators intended for operation. (6)

b) (i) Sketch a reverse power trip. (5)

(ii) Briefly explain the principle on which the operation of this power trip is based and how tripping is activated. (5)

Q3. With reference to U.M.S. operations:
a) State with reasons the essential requirements for unattended machinery spaces. (8)
b) As ETO, describe how you would respond to the irretrievable failure of the Machinery space fire alarm system whilst the ship is on voyage. (8)

Q4. A) Explain the potential hazards if liquid-cooled transformers are used. (6)
b) What are the losses in transformers? Mention the various factors which affect these losses. In a 25 KVA, 3300/233 V, single phase transformer, the iron and full-load Cu. Losses are respectively 350 and 400 w. Calculate the efficiency at half-full load 0.8 power factor. (10)

Q5. a) List the factors that determine the starting torque of the three-phase induction motor. How does this torque generally compare with the value of the rated torque? (6)
b) The low-voltage release of an a.c. motor-starter consists of a solenoid into which an iron plunger is drawn against a spring. The resistance of the solenoid is 35 ohm. When connected to a 220 V, 50 Hz, a.c. supply the current taken is at first 2 A, and when the plunger is drawn into the “full-in” position the current falls to 0.7 A. Calculate the inductance of the solenoid for both positions of the plunger, and the maximum value of flux-linkages in weber-turns for the “full-in” position of the plunger. (10)

Q6. A) With the aid of delta and star connection diagrams, state the basic equation from which the delta-star and star- delta conversion equation can be derived. (6)
B) Three batteries A, B, and C have their negative terminals connected together. Between the positive terminals of A and B there is a resistor of 0.5 ohm and between B and C there is a resistor of 0.3 ohm
Specifications of the three batteries are given below.
Battery A 105 V, Internal resistance   0.25 ohm
Battery B 100 V, Internal resistance   0.2 ohm
Battery C   95 V, Internal resistance   0.25 ohm
Determine the current values in the two resistors and the power dissipated by them. (10)

Q7. With reference to an emergency fire pump state
a) The regulations that influence its location, capacity, and power. (7)
b) How the power supply to emergency pump is ensured? (5)
c) Why a relief valve is necessary on the deck main? (4)

Q8. a) Sketch and describe a total flooding CO2 gas system suitable for the protection of machinery spaces. (8)

b) State, with reasons, which valve should be operated first in the system shown in (a).  (8)

Q9. State how safety is achieved with regard to gas emission in battery rooms where a large number of lead-acid cells are stored with reference to
a) Provision of lighting (4)
b) Ventilation if a fan is fitted (4)
c) Type of distilled water container for topping up (4)
d) Use of tools and replacement of defective batteries (4)