During the overhaul of the Main Engine exhaust valve, the drop-down test should be always carried out. Failure to do so may result in the exhaust valve remaining in partially open condition or fully open condition and malfunctioning as a result. This due to worn out seal rings on the airside of the exhaust valve over a period of time. In several cases, there have been engine starting problems experienced due to this as the compression pressure does not develop. The sealing rings in the air cylinder should be replaced as per the maker's recommendations.
After assembly of the exhaust valve , it is recommended to test the valve in the following way:
- Lift up the exhaust valve with the engine room crane ( which makes the valve open). Connect compressed air to the Nonreturn valve on the air cylinder. The valve should now close.
- By disconnecting the compressed air supply and by venting the air cylinder, the exhaust valve should open.
- After doing this a couple of times, leave the valve closed and shut off the compressed air. The valve should remain closed for at least an hour.
Important note: The air supply to the valve must always be connected before starting the camshaft / LO pumps. This is very important, otherwise, the valve will open more than normal.
