LINER DAMAGE - MAIN ENGINE B & W 6L60 MC
24th May 04
Ship was heading towards Haldia dock gates with Pilot onboard. Suddenly No. 4 unit of Main Engine exhaust gas temperature shot very high. Checked fuel pump fuel regulating shaft for functioning; found the fuel rack free and rotating fine.
After this the fuel rack was pulled back to reduce the amount of fuel injected into the system. Still temp not coming down. Since ship was entering lock-gates pilot didn't allow the engines to be stopped for checking the reason for eng temp increase.
After this a heavy knocking & banging noise was heard near #4 unit exh. v/v, which gradually increased and was heard through out the full length of the unit from exh v/v to crankcase. Very few movements were given after this.
After berthing the engine under-piston space was opened up, and found the liner broken into two halves at the scavenge ports.
The broken cyl liner piece was lying on the diaphragm. Exh v/v removed and found a part of the spindle broken, this piece had fallen and it had come inbetween the piston and liner scavenge port; during upward movement of piston it had caused the liner to break.
This particular v/v spindle had been reconditioned more than 3 times (ie) by building up parent material and stellite coating and then machining. As per B&W, the v/v spindle should not be reconditioned more than twice. So, as the actual parent metal had been removed in due course of reconditioning it had resulted in spindle material loosing its strength and eventually breaking of the v/v spindle.