Problems with the compressor’s main oil pump
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I have a question I’d like to ask everyone. Both the main oil pump and the auxiliary oil pump in the compressor are screw pumps. The main oil pump is driven directly by the compressor’s main shaft through a coupling; it starts operating simultaneously with the compressor. The auxiliary oil pump, on the other hand, is driven by a separate motor, and it starts before the compressor does. A thin tube connects the auxiliary oil pump to the main oil pump, allowing oil to be supplied to the latter. The problem now is that after the compressor starts operating, it sometimes takes a very long time for the main oil pump to build up pressure (the time required to achieve pressure each time the machine is started varies; on several occasions, even after the auxiliary oil pump stopped after 2 minutes as per the setting, the main oil pump still failed to generate pressure, requiring the auxiliary oil pump to be started several times). When pressure cannot be generated, disconnect the tee at the upper end of the main oil pump, and air will emerge. I’d like to ask what the problem is?
The filling pump didn’t fill it properly! It is recommended to properly vent the air when filling the pump; ideally, do this after the compressor starts up (in other words, vent the air also after the main oil pump starts, while it is in operation)
The solution is to drill a small hole in the valve disc of the check valve at the outlet of the main oil pump; 1 mm is sufficient. There’s no need to explain the principle; you’ll understand what’s going on if you think about it. I remember that this solution is also recommended in API 614.
We have this type of compressor here. There is a pipeline connecting the main oil pump and the auxiliary oil pump; it seems that you haven’t carried out the pumping operation for the shaft end pump, which is why there is a large amount of air and insufficient oil supply! In the future, just turn on the priming pump line before starting the main pump!
It’s indeed being done now; the key point is that this didn’t happen before, but it happens every time recently, which is quite strange
It’s done by the filling pump; the auxiliary oil pump starts one day earlier and continues to feed oil to the main oil pump. When the compressor isn’t running, it was checked that there was oil in the tee connection at the top of the main oil pump, with no air present, but air appears once the compressor starts operating
Has the lubricant been checked to see if there is water in it or if there are leaks inside the compressor?
Lubricant has always been tested, and there are no issues; there is also no oil leakage from the compressor, with the oil level remaining essentially unchanged
The instructions should be checked; they contain the operating methods.
Is it because there are gas residues in the main oil pump that prevent it from being properly filled?
Is there a filter at the oil pump inlet? It would be best to check it if possible. Before starting the machine, activate the auxiliary oil pump and the priming pump line; open the exhaust valve and also turn the crankshaft