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The most common reason for the difficulty in operating the main engine is that the suction valve of individual high-pressure oil pumps in the main engine is stuck, the needle valve of the oil head is stuck, the exhaust valve is severely eroded, and the piston is broken, causing the compression pressure to fail to meet the ignition conditions;
Another common fault is improper adjustment of the distance between the thrust flange and the sealing end face of the high-pressure oil pipe of the exhaust valve, which causes serious leakage and direct backflow of camshaft oil at the high-pressure oil pipe joint of the exhaust valve, making the exhaust valve unable to open normally. This situation usually occurs when the exhaust valve is just replaced.
2, Reasons and solutions for the failure of single cylinder ignition in the main engine
1. Malfunctions caused by reversing mechanism
1) One of the reasons is that the car clock handle was placed in the starting position for too short a time, resulting in some cylinders not being able to change direction. If one cylinder cannot be changed direction, it is difficult to accelerate normally.
2) The second reason is that the sealing of the reversing cylinder causes severe aging, leading to air leakage, or the reversing mechanism gets stuck, which can also cause the single cylinder to fail to ignite.
2. Reasons and solutions for faults caused by insufficient compressed air pressure of exhaust valve air spring
1) The common cause of insufficient compressed air pressure in the air spring, excluding faults in the control air system, is due to aging of the exhaust valve air spring cylinder seal and severe air leakage caused by worn copper sleeves.
The long-term response measures must dismantle the exhaust valve, replace the corresponding sealing ring, copper sleeve, etc;
2) If the exhaust valve stem is severely worn, it can also cause a large amount of compressed air leakage from the air spring, and because the leakage distance is relatively short and the leakage speed is fast, it can also cause insufficient compressed air pressure in the air spring.
3. Malfunction caused by intake of camshaft oil system
1) The intake of the camshaft system is generally drawn in by the camshaft oil pump from the disc or suction pipe.
2) Leakage of fuel from the high-pressure fuel pump into the camshaft system can increase the viscosity of the camshaft oil, and the suction vacuum of the camshaft oil pump is too high, which can easily cause the camshaft oil system to suck air. Therefore, the oil in the camshaft oil tank should be replaced regularly.
Moreover, the condition of the high-pressure oil pump components and their sealing devices of the exhaust valve is also crucial.
4. Malfunctions caused by the remote control system of the host
In terms of the remote control system of the host, taking the B&W 5L50MC as an example: if the oil stop delay relief valve (25 # valve) does not work properly, it will cause the high-pressure oil pump to not supply oil in a timely manner, resulting in difficulty in starting. The cylinder in poor condition cannot reach the ignition speed, causing starting failure;
If the delay adjustment of valve 32 # is improper, the opening delay of the main starting valve is too short, and the oil and gas merging time is too short, it will also cause difficulty in starting the vehicle.
Therefore, valves such as 25 #, 26 #, 117 #, 32 #, 33 #, and 274 # should be regularly disassembled, inspected, and cleaned. It is best to replace the repair kit for the main remote control system every 5-8 years.
5. Malfunction caused by exhaust valve air throttle pipe
Some B&W 5L50 models of ships do not have sealed air throttling pipes installed on their main engine exhaust valves, or the diameter of the throttling holes of the throttling pipes is enlarged, so that the air spring air chamber and the sealed air chamber are directly connected. The compressed air of the air spring will be released into the flue through the gap between the valve stem and the guide sleeve, causing a decrease in the compressed air pressure of the air spring and resulting in changes in the timing of the exhaust valve. Cylinders with severe leakage will not ignite, or it will be difficult to start the car when reversing (because reversing consumes more air and is not easy to start).