Prevention and control measures for high-pressure hydrogen-containing areas

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This post was last edited by Wang Xiaoxiaobai Bai on 2016-2-10 at 11:48. The Spring Festival is already half over, and it’s time for everyone to return to work. With a new year comes new opportunities; the person who started this thread is currently facing a major overhaul of the entire plant. Recently, I’ve been collecting some accident reports as material for safety training, and I’d like to share one of them with you. Here is the account of the accident: On X month X, X year, at exactly X o’clock, X, the shift supervisor of the hydrocracking unit, noticed slight leakage and smoking at the packing of the first valve in the refined oil outlet pipeline of the refined oil sampler (the operating pressure in the refined oil reactor was 15.1 MPa, and the operating temperature was 382 degrees). He immediately reported this to the technical officer X. At X minutes, technical officer X arrived at the site to conduct an inspection. During this inspection, it was discovered that the leakage at the valve’s packing had suddenly increased; a large amount of oil and gas was spraying out from the valve’s packing and stem. The two individuals immediately left the site and contacted the control room as well as the fire department. The plant activated its emergency response plan. At X minutes past X, the plant’s management, technical officers, and the shift supervisor entered the site wearing positive-pressure respirators. At 12:23, the four of them managed to close the valve, and the leakage stopped, allowing the plant to resume normal operations. The above is a brief account of the accident. The original poster might as well explain the process characteristics of hydrogenation units: these are processes that involve high temperatures, high pressures, and toxic or harmful substances, and they fall under the category of production processes that require special monitoring due to their ‘two key aspects and one major risk’. Its reaction system is a high-pressure hydrogen-rich environment, containing large amounts of hydrogen and hydrogen sulfide. Hydrogenation units generally include hydrocracking, wax oil hydrogenation, gasoline and diesel hydrogenation, as well as the more challenging residue oil hydrogenation. Hydrocracking units are among the units with higher operational complexity in hydrogenation processes. The operating pressure in these reaction systems is generally above 14 MPa. They consist of two reactors: a refined oil reactor and a cracking reactor, and the operating temperature in these reactors is usually above 370 degrees Celsius. As for hydroprocessing units for gasoline and diesel, they also operate under high-pressure conditions, with the temperature in such high-pressure hydrogen environments being above 300 degrees Celsius. As can be seen from the above accidents, the location of this leakage is at the packing of the first-stage valve of a sampler on the discharge line at the bottom of the refining reactor; this valve is a high-pressure welded valve, a valve without flanges. When the filler leaked, a large amount of hydrogen was released, and there was a heating furnace right next to the reactor; if not controlled in time, the consequences would be catastrophic. In retrospect, for a sampler that is directly connected to high-pressure hydrogen-containing areas, it can be said that the significant risks associated with its use were not taken into account during the design phase. During the operation of the facility, our leaders and technical personnel also failed to consider the need to take emergency measures such as shutting down operations if there were issues with the quality of the sampling valves. It can be said that we have some issues with the risk assessment of processes and equipment, as the risk assessment and identification of critical components are not adequate. I am sharing this experience from the accident with everyone, hoping that you will pay more attention to identifying risks related to process and equipment failures, and that risk management measures will be put into practice. Comrades, you may also share your own opinions.