Faults Caused by Cracks in The Generator Cylinder Head

During the operation of the diesel generator, the coolant temperature was too high. After the shutdown inspection, it was found that the coolant in the radiator was insufficient. After adding enough coolant, the fault was eliminated, but after running for a period of time, the fault reappeared. During the shutdown inspection, it was found that there was a significant decrease in coolant in the radiator.

When the valve cover was removed for inspection, a small amount of white foam was found on the generator cylinder head, while the generator oil did not increase significantly, indicating that a small amount of coolant leaked into the lubricating oil. The above phenomenon indicates that the coolant was evaporated, that is, there may be cracks in the cylinder head or cylinder liner and other components, which led to the formation of negative pressure in the cylinder during the intake stroke. The coolant entered the cylinder from the cracks, and the compression and power stroke, Part of the coolant vaporizes under the action of high temperature. During the exhaust stroke, a large amount of vaporized coolant is discharged into the atmosphere, resulting in excessive consumption of coolant, while a small amount of residual coolant flows into the oil pan along the cylinder wall, resulting in a small amount of coolant in the lubricating oil and generating flesh colored foam.

Inspect the generator cylinder head and liner. After removing the cylinder head, it was found that the first cylinder had severe carbon deposition and there was water on the top of the piston, indicating that there was coolant leakage in the crossover cylinder. However, no cracks were found during the inspection of the cylinder liner. A hydraulic test was conducted on the cylinder head and it was found that water flowed out from the exhaust valve of the first cylinder. When disassembling the factory exhaust valve, a clearly visible crack was found near the valve seat on the cylinder head, indicating that the coolant was leaking from here.

When inspecting the generator cylinder head, it was found that there was a thick layer of scale on the inner wall of the water jacket. Due to the high temperature near the exhaust valve seat, poor heat dissipation efficiency, and thin structure, the thermal insulation effect of scale further deteriorates the heat dissipation conditions, resulting in cracks under the effect of stress concentration‘ After troubleshooting, replace the cylinder head and clean the water jacket before installing and testing the unit, the problem is resolved.

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