Issues related to compressor auxiliary oil pumps causing shutdowns
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The compressors in one of our company’s workshops are reciprocating piston compressors; last year, the shaft end pumps were removed, and gear oil pumps from the light oil station, one in operation and one as a backup, are now used to supply oil to the lubrication points. Recently, two abnormal situations occurred: in one case, a problem with the gear oil pump at the light oil station caused the oil pressure to drop (the normal level is around 0.4 MPa), while in another case, the oil pressure shown in the system’s pipelines dropped to zero before the oil pump reached the pressure required for automatic startup (0.15 MPa). It causes a brief drop out of the vehicle. The operator restarted it, and normal operation was restored with no further issues. Could everyone please help analyze what might be the cause of such an anomaly?
1. Is there an interlock that activates the backup oil pump automatically when the pressure drops too low?； 2. After replacing the shaft-mounted pump with a gear pump, was an interlock test conducted for starting the standby pump automatically when the lubrication oil pressure drops? It is likely that the interlock threshold value was set a bit too low.
Tests were conducted earlier, and the pressure setting was also predetermined; I don’t know why this situation is occurring now.
It is unclear what the settings are for the pressure relief system and/or the pressure switch in your lubrication system. Based on your description, there should be at least two pressure transmitters: 1. One pressure transmitter (Pressure Transmitter 1) is linked to the backup pump. When the pressure is below 0.15 MPa, start the backup pump ； 2. Another pressure transmitter (Pressure Transmitter 2) monitors the pressure of the lubricating oil system. When the pressure falls below a certain value of 0.15 MPa, the compressor shuts down in sequence. The problem you are describing now is that when pressure gauge 1 shows that the pressure is still above 0.15 MPa and the backup oil pump has not started, pressure gauge 2 indicates a pressure of 0, which causes the compressor to shut down as a result of the interlock mechanism. Right? There are several scenarios in this situation: 1. You need to calibrate two pressure transmitters. Especially when pressure transducer 2 is not a pressure transducer but rather a pressure switch ； 2. Check the installation locations of the two transducers; if the installation location of transducer 2 is further from the lubrication point than that of transducer 1, special attention should be paid to this ； 3. Check the piping system for any areas where the slope is inconsistent. One possible reason is that some air is dissolved in the lubricating oil; when the temperature rises, this air moves to the higher points in the pipeline and is compressed there. When the pressure drops, the volume increases rapidly and escapes from some point in the pipeline (for example, downstream of the lubricating oil), resulting in a local drop in pressure. 4. It is advisable to thoroughly purge the pressure gauge by releasing air from it. Note: The poster’s pictures are really beautiful; they’re my favorite style~~~/ :lol
The answer was excellent. Thank you to the kind person! !
There is another scenario: since there is no accumulator in the pipeline, when one pump fails and stops supplying oil, the oil pressure drops too rapidly. The system does not have enough time to react, nor can it wait for the backup pump to reach its normal operating speed and raise the oil pressure again; by that point, the pressure has already reached the value that triggers an interlocked shutdown. Therefore, the auto-start pressure for the standby pump can be set higher; if it is normally 0.4, it can be adjusted to around 0.25 to give it sufficient time to respond. Another aspect is the addition of electrical interlocks; it seems that the response time of electrical interlocks is slightly shorter than that of the system.
This problem arose mainly due to the removal of the shaft-end pump and the use only of the oil station’s oil pump for supplying oil; it was primarily related to the speed at which the instruments responded. Later, plans were made to use new programming to adjust and modify the system.