Simple structure, high pressure cut-off valve can through the valve stem rotation and the principle of elevator, the valve open or truncation, and ensure that the valve seal and seal function. Due to the special structure of movement principle, and also causes stress between the valve seal is extremely adverse consequences (form both the sealing pair must be vertical pressure, and the relative slip between vice friction sealing). Practice has proved that the valve on the seal tend to open/close a few times, just because the sealing pair of scratches and cause leakage. Serious to scratch scratch slightly open repair, are scrapped due to damage, so the consequences of not only increases the manufacturing cost, and the impact on the performance of the valve. To solve these problems to the valve seal structure and materials tested and improved.
(1) The valve stem seal on the part of the move onto the disc (purpose is in the process of loading, the valve sealing surface on the relative cover on the sealing surface in the state of static no slip on). The improved though can increase the seal life, but due to increased between a disc cover and disc sealing structure is relatively complex, price is low.
(2) Change the seal material. Surfacing on the stem seal cone abrasion resistance good department too hard alloy, although this method obtains a good effect, but on the one hand, because the company too alloy cost is too high, on the other hand, due to the basic material for 13 cr martensitic stainless steel stem, poor weldability, welding preheating before welding, when the complex heat preservation after welding and welding process. In addition, to ensure the dimensional accuracy of the valve stem, but also increase the rough machining process. Comprehensive analysis, in addition to the special requirements, which the price is not good.
Practice has proved that improve the high pressure cut-off valve stem cone hardness is a feasible way to improve the globe valve seal life.