Help: Accident occurred where the main fan vent valve of the catalytic converter vehicle suddenly opened

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At around 8:11 a.m., the main operator in charge of the reaction process detected an alarm indicating that the differential pressure between the two reactors had exceeded the allowable limits; he immediately stopped the feed, and the control system switched to safety mode. At around 8:14, the instruments showed a rapid increase in pressure, prompting an on-site inspection of the main fan, where it was found that the vent valve had been opened. A thorough inspection of the instruments afterward revealed no abnormalities. To prevent similar situations from occurring again, it was decided to remove the valve positioner and replace it with the positioner for the backup fan’s vent valve. After investigation, 1. The operational trends in terms of process are stable and normal, so operational factors can be ruled out ； 2. The dynamic wind pressure is normal, and the power supply is normal ； 3. The historical trend signal of the valve position opening degree has not been lost ； 4. The locator has stable performance ； 5. No human factors occurred. It is worth noting that the vent valve was opened, while the inlet valve was not closed. To date, the exact cause of this accident has not been determined. I would appreciate any insights from those who are more knowledgeable; thank you! ! !