The DEH has tripped – let’s discuss it!
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The day before yesterday, while the unit was operating normally, it was discovered that the ETS in the DCS had not been reset – what a serious mistake! After repeatedly verifying that there were no issues with the configuration and no shutdown signals, and since there were no adverse effects, it seemed appropriate to activate ETS; so I clicked to reset it. . . . The AST solenoid valve was not powered, so the main steam valve did not move; it was only by pulling the circuit breaker for AST that the main steam valve was opened. The trip signal from the EST is not connected to the signal line for generator protection, so the generator will not trip either. Therefore, many people wonder why the machine was able to start up and generate power even though the ETS had not been reset. After pressing reset, the DEH tripped :,’(; it became a motor, and the system voltage dropped to over 8,000. No protection at all – a generator powered by hand. Subsequent analysis showed that when the reset button was pressed, solenoids 1 and 2 for exhaust were activated, which caused a brief drop in oil pressure and led to the shutdown of ASL. However, in the DEH trend, none of the three trip signals selected by the three-to-two logic triggered an alarm or caused a trip; yet the ASL based on the three-to-two logic issued an alarm, which resulted in the DEH logic shutting down the system. The light accident analysis meeting lasted for a day. Criticism sessions, huh. Who do you say I should go to for justice? . .
The ETS has not been reset, which means that all the protections of the turbine are not functioning! Naked running, otherwise I wouldn’t take such a big risk by trying to reset it. Who do you think I can go to for justice? Fines don’t really matter. It’s strange though that the safety oil pressure drops; normally, moving these two exhaust valves shouldn’t have such a significant impact on the oil pressure. I plan to conduct an experiment during the next shutdown.
Is there a logical issue with which company’s phone service is being used?
Such a critical reset switch should be one of the conditions for \"allowing startup\" (and if necessary, there should also be audible and visual alarm indicators); the program shall not proceed without \"resetting\". Try to avoid relying on assumptions. Let go of the burdens – the work still needs to be done! Summarize carefully and learn from the lessons.
Reply to hzh04213: The electronic controller is from GE Xinhua; the logic is fine – it’s still an issue with the safety oil pressure. Checking the historical data shows that the safety oil pressure indeed dropped. But why there is a pressure drop is indeed a problem; we need to examine the hydraulic piping. oatobnus: It’s true that the workshop started operating without resetting it according to ETS; this is a serious issue with regard to operations, and better management is needed in the future.
It’s strange; how can it start without being reset! Resetting is part of the necessary conditions for startup. Many of our motors must be pressed to reset before they can start; it is impossible to start them unless the reset button is short-circuited. It is recommended to check the program; oatobnus is right – do not use software-based methods. It’s okay; every mistake teaches us a lesson. The original poster is right to do this, but there is a procedural issue. The correct procedure for dealing with this situation is: report it immediately – hold an analysis meeting at a higher level – come up with solutions – make a decision by the management – and then have the instrument operators carry out the actions.
Reply to wangtosea: The ETS signal operates through four components: 1. The AST solenoid valve, which is used to close the main steam valve； 2. Pumping valves for steps 1 and 2 ； 3. Send it to the generator protection device to trip the generator ； Why was it possible to start the machine at that time when the ETS signal was not reset: The power supply to the AST solenoid valve was not connected, and the signal wire for generator protection had been removed. The valves in sections 1 and 2 are controlled by ETS signals, but they were not operated or used at that time. The configuration program is fine. During that reset, the security oil pressure dropped from 1.08 to 0.83, the DEH’s ASL tripped, and the system underwent a logical shutdown – this is normal behavior. There is indeed a problem with the handler; if something goes wrong, one has to take responsibility – there’s nothing that can be done about that. The key is for me to find out the cause. If no problem is found with the hydraulic system, it can only be attributed to a random occurrence. I think if I were given another chance, I would still order it:lol
Seeing that the guys are still discussing it, I’ll say a few words too. "I will not give up until the issue is resolved,” especially since I am the one involved. I really agree with and admire this work attitude, resilience, and mindset. But one thing – what I say might not be correct – and I still want to remind you: saying \"I think if I were given another chance, I would still order it\" shows a great sense of determination, as if saying \"No one else but me can do it!\" I disagree with you. First of all, such situations are not allowed to occur again in production facilities that are operating normally; if they do happen, the consequences for those involved are very severe, and it can even affect your future within this company (we take such situations very seriously). Secondly, I believe this situation is by no means accidental; production facilities definitely require that problems be identified and resolved. Thirdly, based on the final design documents and drawings, focus is placed on the end stage; checking from back (DEH shutdown signal) to front (pressure sampling points), with particular attention paid to the fluctuations in oil pressure that occur as a result of the operation of the electro-hydraulic conversion device. Fourthly, it is essential to clearly define the boundaries of responsibilities between the instruments and the process; otherwise, the instruments will be doomed.
Thank you for oatobnus’s reply: The phrase “I think if I were given another chance, I would still place the order” is really just meant to comfort oneself, haha. Indeed, there are many irregularities and non-compliances with the procedures in the operation of our crew. This is also a common problem among many small businesses and small-scale units. This is a problem that has accumulated over time, and it can only be improved gradually. I feel a bit like I’m looking at things from a narrow perspective right now. I am also doing my best to prevent the same accident from happening again. Your fourth point is excellent; responsibilities must be clearly defined, and I will definitely take on what is my responsibility.
Recently, the safety oil pressure dropped again; it was the same as before – the drop in pressure caused a shutdown due to the logic control system. No action required. After the brake was re-applied, the safety oil pressure remained low, at around 0.83, whereas it should be 1.09 MPa. The machine was shut down on site, and after the brake was applied again, the pressure showed normal levels. It is suspected that the malfunction was caused by magnetic circuit breaker throttle interference; the cause is still under investigation.
It’s possible that when you attempt to reset, the shutdown conditions are already met; in that case, you don’t need to perform the reset. It’s also possible that the system shuts down at some other point, and it’s necessary to find out the actual cause.
Good luck! I have a clear conscience!
I support the original poster in conducting in-depth analysis and discussion of the faults; that’s what being technical requires – a spirit of exploration!
Brave enough to turn it on again without figuring out the reason – impressive! In our factory, we follow the principle of “four no-lets-go’s”: L:L:L
The interlock protections involved require operation and involve programming; they must not constitute illegal operations