A case study on the troubleshooting of a switch valve closing on its own

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One morning, the staff on duty the previous night informed that there was an unresolved issue: after the switch valve with identifier LV-1***** was turned on for use, it would suddenly close on its own when no one was operating it in the process control or central monitoring system; it required the operator in the control room to close it first before it could be reopened remotely. Furthermore, the occurrence of this fault is random, and its probability is low. Upon on-site inspection, it was found that the valve in question is a cylinder-type ball valve manufactured by Zhejiang’s Jie Company; the solenoid valve used is model 8551 from Aska, and it is of the adhesive-type design. It operates in a 2/5 mode. Some other information that is not directly related to the operation has been omitted for now. Upon on-site contact with the central control system to remotely switch it, it worked fine when turned on, but the shutdown speed was slow; the delay was estimated to be around 1 minute at that time. However, could this slow delay be related to the irregular way in which the valve is shut down? My judgment is that there is no problem; in other words, regardless of the quality of the solenoid valve, its operating condition is fine – there are no leaks at the various exhaust ports, nor at the cylinder connections. To resolve the issue quickly, a new solenoid valve was used as a replacement, and after that replacement, both the operating speed and the switching performance returned to normal. During the regular afternoon meeting in the workshop the next day to discuss this work process, an incident occurred – there were both right and wrong decisions taken. Once the switching speed returned to normal, the coil and wiring were checked; the wiring was not loose and the wire ends were not oxidized. Since it was a current-sensing coil, it was not possible to determine whether it was conducting or not. The valves were switched on and off several times on site, and everything worked properly. To avoid disrupting production, ensure the proper functioning of the valves, and eliminate potential hazards, I contacted the colleagues in the DCS team at that time and asked them to check the power supply for the solenoid valves as well as the relays; it would be best to replace the relays. At that point, I believed that the solenoid valve itself could not be the cause of delayed valve closure, nor could it lead to problems with automatic shutdown. Whether the valve closes automatically is also related to the power signal. After checking, the Dcs colleague determined that there were no faults with the relay or the power supply; however, after discussing it between us, he replaced the relay to avoid potential problems. The task is complete here; it has been two days, and this issue has not reoccurred so far. Since, in the absence of concrete evidence, both the on-site instruments and the DCS replaced some components, some people might think that this work wasn’t done properly, with unclear responsibilities – it’s not clear whose fault it was. Fellow forum members, what do you think is the problem? Feel free to discuss. I have another question for all of you brothers: how can we determine whether the coil of a intrinsically safe solenoid valve is good or not? Except for the substitution method, thank you