AIR LOSS FROM EXHAUST VALVE SEALING AIR SYSTEM
(Main Engine) -- On sailing out from Dubai found excess air loss from system. As one comp was not able to maintain air pressure, second compressor was started. Once clear off break waters and after pilot getting down, Air leak was checked by isolating deck air & E/R air.
As air consumption was still high, M/E was stopped at a safe position. Control air system, checked and found Exhaust v/v sealing air line pressure regulator malfunctioning resulting in loss of air pressure to sealing air line.
Same rectified & M/E started.
In 1990, A bulk carrier fitted with B&W LMC main Engine, failed to start in Astern while departing from locks at Haldia. Subsequent inspection revealed, Reversing disc, (actuated by air cylinder) had not shifted to Astern position and end position signed blocked. Hence ball valve not opening to allow engine to pass in air.
M/E Instructor opened up and all components inspected found heavy scorning on the running disc and its face mating with distributing disc flared up, resulting in seizure with the body. Hence the reversing disc could not move from ahead to astern.
The scoring on reversing disc was attributed by the rubbing of distributing disc against the running disc. As per the design, a differential area between the sh. Distributing disc drink shaft and its bush, in the assistance of L.O. pressure ( Fed to the bush from main system by banjo) is has to engine that the distributing disc, ie kept clear off the reversing disc during normal running of the M/E. Only during starting cycle, the main air is suppose to push the assembly and cause distributing was to mast against the reversing disc. In this case due to wear on the bushing, the oil was freely draining, without shifting the shaft and distributor disc axially we continued overhauling the distributor once is every two months. Laser in the next docking as per makers instruction a pilot valve was introduced in the air supply LML to distributor to positively alarm air from the distributor, immediately after completion of starting cycle. Worn bush was also renewed.