Maintenance and Repairs

Air Start Pocket Leak

water leak into cylinder head air start pocket on two stroke crosshead engine


Contributed by Mr Upal Hassan



Engine Type: KAWASAKI-MAN-B&W, 9L80MC; Two Stroke, Turbocharged, Directly reversible. Max.Cont.Output: 31830 PS (BHP) / 23410 kW at 83 rpm.


I worked for two terms of 18 months on this type of engine with a well known company, and I saw this problem several times.

While inspecting scavenge manifold in port I found some water accumulated in one of the unit’s under piston space. After careful inspection, I found the source of water. The water was running down the inside wall of the liner. I promptly informed the Japanese 1st Engineer and the ‘under piston space cleaning’, which was going on, was suspended. We took out the exhaust valve casing of that unit, and climbed down to inspect inside the cylinder. The problem was found within a short time. The air starting valve pocket of the cylinder head was leaking cooling water from a small aperture. We changed the cylinder head. The same thing found again in same type of engine in another of the companies vessels. Then a practice was developed in our vessel and in our company. Whenever we changed exhaust valve, we used to gauge the starting air valve pocket for wear."




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