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Think of fire triangle.

In order to understand logically, firstly need to understand how the Main Engine starts on starting air.

Generally speaking, starting air reservoir/bottle -> main starting air valve -> starting air valve (on each M/E cylinder)
For MC engines, starting air distributor controls open/close timing for starting air valve

Extremely helpful reference + photos:
MAN B & W service letter Starting Air System

What are the causes of starting air line explosion on ships ?
The main cause of starting airline explosion is the leaking starting air valve or jamming at open position of the valve.
Initially, the oil which is discharged from the air compressor to starting air line system, it will deposit as a thin moist film on the internal surface of the pipes but not ready to combustion.
If starting air valve leaked or jammed at open position, hot gas or flame may enter the starting air manifold, vaporize the oil and set the fire to oil mist and greasy matters, which generally deposit on the surface.
At that condition, mostly arrival first start for manoeuvring time, high pressure compressed air coming into contact with the fire and may cause explosion.

How to prevent starting the air line explosion ?
– Regular overhaul and maintenance of starting air valve.
– Before departure, test the air starting valve leakage.
– Regular drain off the air bottle drain valve.
– Regular drain off air starting system.
– Regular cleaning of the compressor suction air fitter and use oil wetted suction filter.
– Feed minimum absolute cylinder lubrication to main air compressor.

What are the safety devices on starting air line ?
– Spring loaded safety valve or bursting disc. (if bursting disc fitted, no need for relief valve)
– Flame trap. (At joint where manifold to each cylinder starting line)
– Starting air line drain valve. (Inlet of automatic air starting valve)
– Turning gear interlock
– Reversing interlock

How to test starting air valve leakage of main engine on ships ?
When Engine Running

By hand touch feeling to adjacent pipe to the valve while in engine is operating.
If leak, we can feel the pipe hotter than others.

When Engine Stopped

Shut the isolating valve of starting air distributor
All indicator cocks must be opened
Disengage the turning gear
Open the main air bottle stop valve
Set the control lever to starting position
Check all the indicator cocks
Escape of air through indicator cock will show a leaking starting valve
It should be replaced immediately.

• This topic was modified 3 years, 3 months ago by Admin.

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