Cause of starting air line explosion:

• The main cause of starting airline explosion is the leaking starting air valve or jamming at the open position of the valve.
• Initially, the oil that is discharged from the air compressor to the starting airline system will deposit as a thin, moist film on the internal surface of the pipes but is not ready for combustion.
• If the starting air valve leaks or is jammed at an open position, hot gas or flame may enter the starting air manifold, vaporise the oil and set fire to oil mist and greasy matter, which generally deposit on the surface.
• At that condition, in manoeuvring time, high-pressure compressed air comes into contact with the fire and may cause an explosion.

Preventing starting the airline explosion:

• Regular overhaul and maintenance of starting air valve.
• Before departure, test the air starting valve leakage.
• Regularly drain off the air bottle drain valve.
• Regular drain off air starting system.
• Regular cleaning of the compressor suction air fitter
• Feed minimum absolute cylinder lubrication to the compressor.

Safety devices:

• For direct-reversing main engines with a bore greater than 230 mm, flame arrestors or bursting discs are required for each cylinder and must be fitted between the air start valve and the manifold.
• For non-reversing and auxiliary engines with a bore greater than 230 mm, a single flame arrestor or bursting disc is acceptable, fitted at the supply inlet to the starting air manifold.
• Although not mandated by IACS regulations, a relief valve may be fitted to the manifold in cases where flame arrestors are used instead of bursting discs.

Devices to reduce the severity of an explosion:

• Made of brass or aluminium with high specific heat capacity. Contains multiple holes bored in a circular form to allow air passage.
• Prevents flame propagation from the cylinder back to the manifold.

• Designed to burst at excessive pressure to relieve pressure buildup. Comes with a telltale strip for indication.
• Provides a controlled release of pressure during an explosion. The engine can remain operational by locking escape holes until the disc is replaced.

• Spring-loaded valve that lifts when the manifold pressure exceeds the set limit.
• Releases excess pressure to the atmosphere, preventing further escalation of the explosion.

Attention to be given before standby:

Check if any valve is leaking.

1. Open the air bottle valve and manually open the main air start valve.
2. Isolate the air supply to the starting air distributor.
3. Rotate the engine using the turning gear while keeping the indicator cocks open.
4. If any starting air valve is leaking, air will escape under pressure from the indicator cocks.
5. Replace any leaking starting air valve before putting the engine on standby.