When the start command is given to the engine, control air will open the automatic air start valve and the compressed air will flow to the start air manifold and start air distributor. The start air distributor will supply air to open the air start valve on the main engine whose piston has just passed TDC. The high-pressure compressed air from the manifold will flow into the cylinder, pushing the piston down. As the piston moves down, the other unit, which has just passed TDC, will open the air start valve and bring the engine to the revolutions required for starting the engine.
(b) Safety Devices and Interlocks in the Starting Air System
- Flame Trap/Flame Arrestor: Prevents flames from entering the airlines and reaching the air bottles in case leaking air start valve
- Bursting Disc: Releases excessive pressure in the starting airline
- Relief Valve: Fitted on the starting air manifold to release excessive pressure.
- Non-Return Valve: Prevents hot gases, flames, or sparks from travelling back towards the air bottles in case of a faulty air start valve, minimising the risk of explosion
- Turning Gear Interlock: Prevents the engine from starting if the turning gear is engaged.
- Running Direction Interlock: Ensures the engine will not receive fuel if its running direction does not match the specified direction on the telegraph.
- Starting Air Distributor End Position Interlock: Prevents the engine from starting if the distributor has not reached its correct end position
- Lube Oil Pressure Interlock: Prevents the engine from starting if the lube oil pressure is low
- Auxiliary Blower Interlock: Ensures the engine will not start if the auxiliary blower is not in automatic mode.