【Haichuan’s Insights from Other Sources】Increased leakage at the sealing points of hose connectors; replacing the seals resolved this serious leakage issue

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On August 11, the equipment technician from the Second Refining Department of Cangzhou Refining & Chemicals, along with his team members, had just completed the replacement of the flexible hose at burner No. 15 at the bottom of the heater in Unit 2 hydrogenation plant; they immediately called in LDAR technicians to check for leaks at the connections at both ends of the hose. “Only 5 ppm, with almost no detectable leakage. ”Watching the numbers displayed on the screen, Mi Xiaolong felt relieved; \"The problem with leaks has finally been solved!\" In June of this year, LDAR testers at the Cangzhou Refining and Chemicals Quality and Metrology Center discovered that at several hoses connecting the gas lines to the burners at the bottom of the heating furnace in Unit 2, the leakage levels at both ends of those hoses had increased. Although the indicators meet the local environmental protection requirements, they show an upward trend. Initially, to address this issue, the various teams tried to use pipe wrenches for tightening, but this did not solve the underlying problem. 　　Therefore, the equipment technician from the Second Refining Department of Cangzhou Refining & Chemicals led various teams to form a task force; they shut down the leaking burner and studied the sealing surfaces at both ends of the connecting hoses. They identified the cause of the leak: the burner hoses at both ends of the heater in Hydrogenation Unit 2 were connected using threaded spherical seals; over time, corrosion of the spheres and a decrease in their flatness led to gradual failure of the seals. “Just furnace F4101 has 56 burners, resulting in as many as 336 spherical sealing points. If it is not addressed in a timely manner, the consequences will be severe. ”Mi Xiaolong said. 　　“If an annular groove can be created on the sphere, and an annular sealing ring is made to be semi-embedded in that groove, the problem might be solved. ”Mi Xiaolong suggested. He then contacted various hose manufacturers to request the customization of special hoses. After repeated calculations by Mi Xiaolong and the manufacturer’s technical staff regarding the position, width, and depth of the grooves as well as the size of the sealing ring, the custom parameters for the hose’s sealing sphere were finally determined. 　　On the morning of August 11, the custom-made test hose arrived. After determining the installation plan and implementing safety measures, Mi Xiaolong led everyone to start replacing the hose of burner No. 15, which had the highest leakage rate. 20 minutes later, the first hose was installed. LDAR detection data show that the leakage level at one end is 0, while the leakage level at the other end is only 5 ppm, **which is better than the factory’s specified limits. On that day, all custom hoses were replaced, and the LDAR test values were all below the factory’s specified limits. Only then did Mi Xiaolong’s worried heart finally settle down.