Tripping of the turbine oil pump caused the shutdown
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Recently, one of our units had a compressor driven by a turbine; during operation, the oil pump stopped working due to an electrical fault. The backup pump managed to take over successfully, but the unit still shut down because of low speed-control oil pressure. The quick-shut oil pressure pipeline is equipped with a buffer tank (accumulator). This has happened several times. Dear experts, has anyone encountered a similar situation? How was it solved?
Three things: 1. Check whether the delay setting for the quick-shut oil level low interlock is appropriate, that is, the allowable time for fluctuations; generally, the delay is 3-5 seconds； 2. The pressure of the internal air bag in an accumulator should be checked regularly to ensure it is at the designed value, which is generally 60-85% of the oil pressure. 3. An accumulator isn’t complete just by being installed; before starting the machine, a test should be conducted to verify that the main pump shuts down while the auxiliary pump starts up in a cold state. This involves closing the main steam valve and forcing the quick-shut valve to open, in order to check for any shutdown signals. I think my ** is perfect already; I’m asking for the best assistance and response
Thank you! It has been restarted due to production load requirements. No further inspection was carried out on the accumulator. We also conducted tests before driving: by manually stopping the operating pump, the standby pump started up immediately, and within less than a second the oil pressure dropped to 0.3 MPa, triggering an automatic shutdown signal. Our oil pump has two self-start conditions: 1. The oil pressure at the pump outlet is below 0.85 MPa, 2. An electrical stop signal for the main pump.
If it drops to 0.3, it should be impossible to save anything; then it can’t just be the oil pressure – due to the chain shutdown, the quick-close valve will close on its own, overcoming a pressure of 0.3
Another possibility is worth checking: after the main oil pump stops operating and the auxiliary oil pump starts, see if the pressure at the pump outlet increases; or, if it starts too early, check whether the safety valve will trip again due to the high pressure
The quick-shut oil pressure is essentially equal to the control oil pressure. There are several possible reasons for the secondary pump to start automatically due to insufficient quick-shut oil pressure: 1. The pressure setting for automatic startup of the secondary pump is unreasonable and too low. Generally, there are three criteria that can trigger the automatic startup of the secondary pump: first, when the lubricating oil pressure drops below 0.15 MPa; second, when the control oil pressure falls below 0.6 MPa; third, when the lubricating oil pressure drops below 0.9 MPa after the filter has cooled down. The secondary pump will start automatically once any of these conditions is met ； If any of these three points starts up on its own, I don’t think the shutdown interlock you mentioned will occur. 2. The shutdown pressure for rapid shutdown is too low, while the maximum allowable value is too high; generally, the interlock threshold for rapid shutdown is 0.15 MPa. 3. There are issues with the lubricating oil pipeline, the system capacity is too large, and the buffer volume of the accumulator is insufficient, meaning that the appropriate size was not selected.