1. The use of stainless steel bellows shut-off valve installed in the pipeline of marine power plant, the valve stem occurred at the valve during the use of leakage and stem rust and other issues, although the repair. But problems recur. After analysis of the cause of the malfunction, take appropriate solutions to eliminate the failure to ensure the performance of the valve. 2. Analysis of the problem Stainless steel bellows valve leakage is generally divided into internal leakage and leakage of two cases, causing more leakage. Endocrine is generally due to the number of liquid medium containing solid impurities damage sealing surface caused failure. Combined with field use analysis, the main reason for valve stem leakage is related to the structure of the valve, working environment and operation mode of operation. 2.1 Structure The valve stem adopts corrugated pipe and packing double seal structure. The bellows is welded with inner lining ring and outer lining ring into bellows assembly, and then welded with valve stem and guide body to block leakage of medium through valve stem. Upward and downward movement of the stem flat key â… upward movement, until the flat key â… and the lower end of the lower end surface of the filler in contact. As the underfill material is made of PTFE material, if the valve is opened excessively, the flat key I will be embedded in the filler, the valve can not be opened and closed, and the bellow assembly will be hit, causing the leakage of the medium along the stem. Corrugated tube length and amount of compression is determined according to the valve stroke, if the limit of stretching or compression, it may damage the bellows, resulting in rupture of a small tube, seal failure. Therefore, the need to increase the valve opening and closing of the limit device, making the valve opening and closing process, the bellows has been in the design range of telescopic. 2.2 Working environment Corrugated pipe shut-off valve poor working conditions is one of the causes of its failure. As the bellows installed in the hull of the long-term work in salt spray environment, and the upper often condensate dripping, resulting in the upper thrust ball bearings corrosion, serious, resulting in contact with the stem corrosion 2.3 operation in use if excessive Opening or closing the bellows shut-off valve may result in the valve not meeting the performance requirements. When the valve is closed excessively, it is possible to crush the sealing surface, resulting in failure of the seal when the valve is used again. When the valve is opened excessively, the bellows assembly may be operated, causing the valve to leak. 3. Improve After analyzing the valve problems, its structure, operation and the environment has been improved. The first is to increase the flat key â… limit welfare fee, the PTFE material under the filler asked to add a thick 3? Stainless steel filler pad to prevent stuffing becomes dirty and the valve stem limit. When the valve is closed, if the valve can not be closed, it should not be forced to close. Instead, the valve should be opened and closed again after fluid is washed for a period of time. If the valve still can not be closed, the sealing surface should be inspected. When the valve is open, when the valve is opened to a certain height, the stem encounters a small resistance, try not to continue to force open, in order to extend the life of the stem and seal components ah. Valve stem with thrust ball bearings on the top of the globe valve, when installed, we should try to avoid there is a direct drop of condensed water in the valve account of the valve stem corrosion caused by the position. 4. Conclusion bellows shut-off valve improved, there is no recurrence of bellows cracking, stem rust and leakage and other failures, the use of good. More keyword search: globe valve, stainless steel bellows
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