The incredible malfunctions that occurred during operation in those years, Part 2 – 2 auxiliary oil pumps failed consecutively

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Actually, this fault occurred simultaneously with the fault in Series 1: https://bbs.hcbbs.com/thread-3238295-1-1.html. As mentioned earlier, when the compressor started up, during the initial phase, the temperature of the lubricating oil rose from 38°C to 65°C, which triggered a shutdown. This process lasted for about 40 minutes. According to the compressor’s shutdown logic, the auxiliary oil pump should have started up after the shutdown, but something strange happened – as soon as the auxiliary oil pump began to operate, an overload alarm appeared on the MCC panel. Upon inspection, it was confirmed that the motor had indeed stopped. The coupling cover was removed and the pump was tried to be rotated; it wouldn’t turn. The coupling was disassembled, and the motor could be rotated, but the pump still wouldn’t move. There was no other choice; due to the urgency to get the system up and running, we had to remove the auxiliary oil pump from another unit that hadn’t been tuned yet and install it in place, then try to start the machine again for testing. Yet, the same fault occurred as before. After more than 40 minutes, the oil temperature reached the high alarm level, causing the machine to shut down; the auxiliary oil pump started up, but it got stuck. As a result, 2 auxiliary oil pumps were damaged in succession. Manufacturer’s analysis: The reason for the damage to the auxiliary oil pump may be the high temperature inside the fuel tank at the time of shutdown (above 72°C). After the shutdown, the auxiliary oil pump started operating; it was winter at that time, and it took more than 40 minutes for the auxiliary oil pump to return to normal temperature. The hot lubricating oil flowing through the pump caused its temperature to rise suddenly, resulting in uneven heating of the rotor’s moving and stationary parts. This led to expansion and deformation of the rotor, causing it to get stuck. The solution provided by the manufacturer is to make a hole of φ2mm at the position of the valve core in the check valve at the outlet of the auxiliary oil pump. This ensures that, when the main oil pump is operating, lubricating oil at a higher temperature can flow back through the auxiliary oil pump at any time, thereby maintaining its temperature. As a result, after shutdown, the auxiliary oil pump will not be damaged due to excessive temperature differences when it is started up again. After drilling a hole in the spool of the outlet check valve, we started the unit again; after operating for about 40 minutes, the oil temperature rose to the shutdown level once more, causing the unit to stop. However, at this time the auxiliary oil pump was functioning properly, and there was no rotor seizure issue. Well, it’s astonishing that the manufacturer made such a basic mistake. If we look at the lubrication systems of other units, we’ll find that the check valves at the outlets of the auxiliary pumps all have small holes in them. Actually, this isn’t that strange of a situation. But this compressor still has even more bizarre faults waiting to be discovered; I’ll talk about those next time