Air Starting System Q6-7 Page 6

Question 1

List five important safety features fitted to a main engine air starting system.

Answer 1

1. Pressure relief valves on each branch of the main air starting manifold.
2. Non-return valves leading from the main start manifold to the main air receivers.
3. Safety interlocking valves preventing air to be administered whilst turning gear is engaged or fuel.
4. Flame trap gauzes on every air start valve.
5. Pressure relief valves fitted to main air receivers venting to atmosphere.

Additional features include drain valves on air bottles, bursting disc on air start manifold, turning gear interlock, and relief valves and drains on manifold.

Question 2

How may a leaking air start valve be detected?

Answer 2

1. Increase of temperature in pipe leading to manifold.
2. Loud noise coming from the valve (Hissing).

Question 3

What actions should be taken on a leaking air start valve?

Answer 3

1. Raise alarm.
2. Cut off fuel to affected unit.
3. After being given permission, engine should be stopped and air start valve should be replaced if possible.

Question 4

What are the dangers of allowing a leaking air start valve condition to persist?

Answer 4

1. Potential over-pressurization of air starting line due to escaping combustion gases from the unit.
2. Oil explosion within air start line and air receiver due to oil accumulation from carry over from air-compressors.

Question 5

Sketch a simple cross section through an air starting valve for a marine diesel engine.

Answer 5

Pilot Air In
Operating Piston
Closing Spring
Vent
Balance Piston