Puncture Valve

• A puncture valve is fitted in the top cover of the pump. It is opened when compressed air from the control air system acts on top of a piston fitted in the top cover. Fuel oil from the discharge side is then returned to the suction side of the pump and no injection takes place. The puncture valve is operated in the event of actuation of the shut down system (all units), during the air start sequence or when excessive leakage is detected from the double skinned fuel pipes.

• The puncture valve consists of a piston which communicates with the control air system of the engine. In the event of actuation of the shut-down system, and when 'STOP' is activated, compressed air causes the piston with pin to be pressed downward and 'puncture' the oil flow to the fuel valve. As long as the puncture valve is activated, the fuel oil is returned through a pipe to the pump housing, and no injection takes place.

• MAN B&W reversing: Reversal of the fuel pump follower only takes place while the engine is rotating. If the engine has been stopped from running ahead and started astern,the fuel pump follower will move across as the engine starts to rotate and before fuel is admitted by venting the fuel pump via the "puncture" valve.