Control valve in high and low temperature valve is not working properly (5 methods) 1) Unified linear expansion to reduce the leakage of double-seat valve method Double-seat valve at room temperature test, the leakage is not too large. High temperature use of leakage soared.This is because the two seat fixed on the valve seat sealing surface of the linear expansion and spool double sealing surface of the linear expansion of different causes such as a DN50 double seat valve spool Stainless steel, the body is carbon steel, when used at a temperature of 70 ° F at room temperature, the valve seat sealing surface and the spool sealing surface line expansion difference of 0.06mm, so that the leakage increased by up to 10 times. The solution: ①use the valve body and valve are made of the same material, that is, stainless steel valve. However, the price of stainless steel valves than carbon steel valves more than 3 times. Economically speaking; should be considered in this way; ② use sleeve valve instead, because the sealing surface on the sleeve, the sleeve and the plug is the same material. 2) Seat Sealing Soldering At temperatures up to 750 ° F, the threaded seat creates a leak on the sealing surfaces and threads connected to the valve body and can erode the threads, creating the risk of the seat being dropped in the event of a To this failure, should think of the seat seal welded to prevent loose and fall off. 3) Bushing positioning Welding as the spool, the valve plug, stem-oriented bushings, the vast majority of occasions is the static fit. Regulating valve in the room combination of high and low temperature work, due to different linear expansion caused by the diameter with a small change, the occasional interference with the sleeve will meet the least amount of interference, or bushing and spool stuck in the foreign body Spool movement, the bushing will fall off. This failure is not much, but it has occurred. In this regard, the bushing can be positioned lap welding, to ensure that the bushing never fall off. 4) Increase the bushing guide gap method Under high and low temperature, when the shaft diameter and the liner bore diameter expansion of different, and the shaft expansion is greater than the expansion of the bushing hole, the shaft movement or rotation will have a card jump Phenomenon, such as high temperature butterfly valve. If the valve at this time the actual working temperature in line with the requirements of the valve temperature may be the quality of the manufacturer. To solve the problem, it is natural to increase the guidance gap. The easiest way is to guide the small parts of the shaft diameter 0.2 ~ 0.5mm, and should be to improve its finish. 5) Back-to-back packing method Cryogenic cryogenic valve, when cooling due to the formation of a vacuum within the pipeline, from the filler to the body of the vent, the upper layer of double-layer packing or filler can be part of the back-to-back installation to prevent the atmosphere Leak through the stem seal.