Air Start Systems

Question 1

What are the three main sources of explosions in an air start system for a slow speed engine?

Answer 1

1. A leaking start air valve
2. Fuel leaking into the cylinder whilst the engine is stopped
3. Auto ignition of oil deposited on the inner surface of the start air manifold

Question 2

How can you minimise the risk of a start air explosion?

Answer 2

Oil carry over from the compressor should be minimised. Class regs require air compressor air intakes are located in an oil free atmosphere and a drain/filter for intercepting oil/water between compressor discharge and receiver.

Question 3

What is required on the air system for direct reversing engines with a greater bore than 230mm?

Answer 3

The air start system must be protected with flame arresters or bursting discs for each cylinder, fitted between the cylinder start air valve and the manifold.

Question 4

What must be fitted for non-reversing and auxiliary engines with a bore greater than 230mm?

Answer 4

A single flame arrester or bursting disc is acceptable fitted at the supply Inlet to the starting air manifold.

Question 5

What sort of practices can lead to explosions in the main air start system?

Answer 5

• Tell tales/drains at each end of the starting air manifold found blacked off.
• Failure to drain start air receivers and starting air pipes at regular intervals
• Failure to check for leaking start air valves
• Failure to maintain starting air valves and systems in accordance with manufactures instruction.
• Failure to maintain fuel valves