At 7 o’clock today, the air separation unit stopped working again
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During the night shift today, up to 7 a.m., the air separation unit stopped operating again. The cause was once again the sudden full opening of the anti-surge control valve BV9004, which is used to regulate flow from stage 2 to stage 1 of the compressor; this led to a low speed of the expander, triggering a shutdown mechanism. Additionally, the low temperature in the oxygen pipeline caused the liquid oxygen pump to stop working. This valve’s feedback values do not stay within the acceptable range 4-5 times per day, and it automatically opens and closes several times each month. No solution has been found despite attempts to address the issue, and even the manufacturer is at a loss. I think replacing it with a new valve might be a good option – do you have any other suggestions?
Check whether the valve parameters meet the process requirements； Try a different valve positioner ； Appropriately reduce the booster outlet pressure under normal control conditions.
We’ve replaced several positioners, and we also provide special care for the valve by venting it every hour; the pressure is lower than the set value as well. We’ve checked all the parameters, but the problem still persists.
Replacing the valve positioners a few times should resolve the issue; having the pressure setting below the rated value should also not cause problems. Now, check the historical trend data – if the pressure and flow at the operating point are such that the valve opens before reaching the surge zone and remains fully open, then there is likely a problem with the instrument air supply connected to the pressure guiding tube. Disassemble components such as the filter on the instrument air supply tube and clean it by blowing air through it.
It is possible to check whether the valve control signal is being interfered with
Could we analyze whether there is any presence of foreign matter? We have encountered similar situations before; it turned out that debris had gotten into the valve. That debris was caused by a small experiment carried out on site, with dust being blown in, and no one knew or cared about it at the time. As for the more complex aspects, I don’t really understand them; I’m not a chemical engineer, nor have I been involved in production! Perhaps I’m not right; please forgive me!
By the way, the conditions in which this valve operates aren’t very good – there’s an oil fan above it, and there’s a lot of smoke and grease around all the time. But it’s been working fine for 3 years now; it only started having problems today.
Is the cylinder leaking? It’s better to replace the actuator.
That’s so unfortunate~~ It would be best to find some experts to deal with this issue~~ Your factory must have some kind of partnership with a university as well, right? It’s a waste of money to make such a round trip by vehicle; I’ve actually been to an ammonia synthesis plant, and making one such trip costs 1 million……
When these risk factors fail to draw sufficient attention from management, or when operations can continue somehow despite them, then from a practical standpoint, I think it’s not yet time to address them – and this is why the problem has not been resolved satisfactorily to date! As for why this is the case, we can only hope that the parking valve will be disassembled and repaired! Go offline to do experiments! ! ! !