Why do safety valves leak more under steam conditions

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Why do safety valves leak under steam conditions? Regarding Shen Chenglong’s DWMC steam-operated safety valve, it can’t be said to leak excessively; I have identified the following factors that could cause leakage. I. Incorrect selection: The seller chose a conventional type of valve (for gases) for steam applications, which led to differences in material and structure. 1. Steam-elastic valve disc----------Conventional mushroom-shaped valve disc. 2. Material of the steam high-temperature valve core----------Conventional stainless steel. 3. Structure of the steam radiator----------Conventional closed structure. The incorrect selection is due to the following two reasons: 1. The seller’s selection staff made a mistake. 2. The parameters provided by the buyer did not match the actual conditions on site. II. Installation issues: 1. Safety valves are required to be installed vertically according to standard specifications, but they were installed at an angle on site. After the safety valve operates during the commissioning phase, due to its inclined installation, the sealing force exerted by the valve stem after the valve closes is no longer applied to the vertical sealing surface. This results in a reduced sealing force and imbalance, causing the valve to leak as well as to operate prematurely. In the case of overly exaggerated diagrams, according to standard TSG ZF001-2006 – Regulations on Safety Technical Inspections for Safety Valves, during the installation of thermal power safety valves with butt-welded inlets, impurities may remain in the pipelines; when the valve is tested under hot conditions and operates, these impurities fall onto the sealing surfaces, resulting in leaks. III. Operating conditions for which the valve structure is not suitable – I’ll give an example for this. IV. System issues: 1. The system operating pressure (the typical working pressure) is too close to the valve’s set pressure, exceeding the sealing pressure that the valve can withstand. 2. Vibration in the system causes the spring force of the valve to be transmitted to the sealing surface at an angle, which in turn leads to a decrease in the set pressure value and an increase in the percentage of sealing pressure. API-520-2 V. Grinding Issues 1. This issue is mainly manifested as leakage when the seal, which passed the cold-state tests, is subjected to hot-state testing on the test bench (installed in the equipment). The issue of compatibility between the abrasive and the material of the sealing surface, as well as the inspection issues after grinding. Abrasive compatibility: 630 is suitable for corundum, while high-temperature materials are suited for ultra-fine abrasive particles. Inspection and required values after grinding: Flatness inspection in accordance with JBT 7369 – Method for inspecting the flatness of the end faces of mechanical seals. Reference: Analysis of internal leakage in fully open spring steam safety valves – \"Industrial Boilers\" – 2015 (2), pages 36-39. --------------------- Qin Chunqiu