Discuss based on case studies how to safely disconnect the high-temperature control valve for maintenance
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Case summary: On xx month xx day, staff from the Instrumentation and Control Department requested the replacement of the valve core of the radiation control valve FRCxxxx in a certain coking furnace. At around 8:40, the operator switched the control valve to the bypass line, closed the valves upstream and downstream of the control valve, and allowed it to cool down naturally through insulation. 14:02 Re-secure the upstream and downstream valves on the control valve, and confirm that the temperature in front of the control valve has dropped. After protecting it with a steam hose at the service station, the operator slowly opened the front drain valve of the control valve, with technicians monitoring the process. During the first and second attempts to open the drain valve, no residue oil flowed out. At around 14:04, during the third attempt to open the drain valve, high-temperature residue oil sprayed out under pressure; the flow rate increased rapidly, and one minute later the high-temperature residue oil caught fire on its own. The accident caused some control valves, instrument enclosures, pipelines, etc. to be burned out. Note: Coking units contain many rubber powder impurities, which can easily cause blockages. Everyone discussed: 1. How to cut off power safely for maintenance? How to safely release pressure to prevent accidents? 2. How to effectively prevent clogging problems in valves such as drain valves? 3. Discuss how to select appropriate drain valves and where to locate them most effectively
Why isn’t anyone discussing it? Let me add that the cause of the accident in this case was the accumulation of coke dust at the valve core, which led to the upstream valve tube not being in place. As pressure dropped, fluctuations in flow and pressure occurred, causing the coke dust trapped under the valve core to loosen. A large amount of high-temperature residue oil flowed out through the gaps left open beneath the valve core, emerged from the drain nozzles, and caught fire upon contact with air. I hope to see active discussions on this topic, and I’d like to hear the views of experts as well as the general public.