A case study on the troubleshooting of faulty control valves in technical upgrades

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In the afternoon, the supervisor requested that the instruments for a newly installed technical improvement project be calibrated. Right from the start, when attempting to calibrate the control valves, issues arose. There is air supply, but it doesn’t operate; the electric valve has a fault and remains closed. The solenoid valve was switched on and off manually, and everything seemed normal. The explosion-proof junction box was opened to check the power supply; there was no power. The DCS was informed to check whether there was any power output, and it was reported that no load was present and there was no power. Later, it was reported that the issue had been resolved and power was available, but the valve still did not move. A multimeter was used to measure the voltage, and it was found to be very low, below 10 volts. When the wiring terminals were disconnected, the voltage was around 22 volts, which is normal. The nameplate of the solenoid valve was checked, but no voltage indication could be found – only information related to explosion protection and the model number, etc. The positive and negative terminals of the power cable were then replaced. OK. This indicates that the problem lies in two areas: first, the DCS has no output; second, the Asuka solenoid valves with green labels have positive and negative poles that need to be distinguished. This is the first time I’ve encountered a solenoid valve with positive and negative poles but without indicator lights; previously I’ve seen solenoid valves with 220 volts and power indicator lights that also had positive and negative poles. In summary, before debugging, the DCS was not functioning properly, which caused delays. Secondly, the technical staff failed to provide the field instrument operators with detailed information regarding the parameters and models of the instruments that had been installed. Poor communication. .