Discussion on the fluctuation problem of turbine surge valves
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The surge valve of our company’s turbine suddenly opened fully for no apparent reason, then returned to its original position after a few seconds, oscillating back and forth. Initially, we thought it might be a fault with the SMC actuator or poor wiring connections, but none of those issues were found. The hardware from Black Horse was also checked and found to be fine. Upon examining the output of the underlying program, we discovered fluctuations in that output. Has anyone else encountered this problem? Seeking advice
If it is confirmed that the issue is caused by output disturbances, it is recommended to add a delay switch to filter out such abnormal values!
The unit experiences surge fluctuations, and the reasons for these fluctuations are mainly as follows: 1. There are indeed fluctuations in the process; this needs to be confirmed； 2. Fluctuations caused by anti-surge calculations; there are issues with the anti-surge calculations or decoupling – check the configuration ； 3. The controller has no output, but the output from the card fluctuates; check the grounding, such as whether the 24VDC negative terminal is shared for grounding and whether the grounding required by the system is proper. There may also be occasional faults with the card itself; it is recommended to replace the card if possible and send it back to the manufacturer for testing ； 4. The issue with the on-site instruments has been resolved by the author. Additionally, in accordance with API670 requirements, the control functions of the unit, namely speed control, performance control, and anti-surge control, should be separated from the unit’s interlocks. Anti-surge calculation is not Black Horse’s strong point; Black Horse is decent at SIS interlocks, but there are fewer and fewer users for those as well.
We are currently in a shutdown mode; once forced flow and pressure are applied, there will be no more fluctuations. It is suspected that the fluctuations are caused by the flow signal varying around 4 milliamps – when it falls below 4 milliamps, the maximum value is assumed. This has not been verified yet, and we will let you know once it is.
When the anti-surge valve fluctuates, are there devices such as walkie-talkies used in front of the control system? During production, we found that walkie-talkies cause significant signal interference, leading to fluctuations in the throttle valves of the turbine.
We have already checked this specifically, and there is no such issue
If it is below 4 ma (it may be set to 3.8) or above 20 ma (it may be set to 20.xx), the program will consider it a line fault, which will trigger interlock. But you said that since the valve has moved, it should stay in that position; it can’t reset on its own, right? Could it be that what is done in logic is indeed automatic reset rather than manual reset?
It’s not always below 4 milliamps; rather, it fluctuates around that 4 milliamp level