Differences between Soft Sealed Gate Valve and Hard Sealed Gate Valve
Publisher：Botou Valve
Hard seals are the seals between metal and metal. Sealing spheres and seats are metal. Processing accuracy and process are difficult, generally used in high pressure, usually more than 35 MPa. Soft seals are metal and non-metal seals, such as nylon tetrafluoroethylene, which are manufactured in the same standard.
Sealing material: elastic soft sealing gate valve and hard sealing gate valve are the seating material of the valve seat. Hard sealing is precisely processed with the seating material to ensure the matching accuracy with the spool (sphere). Generally, stainless steel and copper are used. Soft seal refers to the sealing material embedded in the valve seat is non-metallic material, because the soft seal material has certain elasticity, so the processing accuracy requirements will be lower than the hard seal.
Manufacturing technology: Because of many chemical industry, the working environment of mechanical industry is more complex, many of them are high temperature and pressure, medium friction resistance is big, corrosive strong, now technology progress, the use of various materials is better, processing and other aspects can keep up, so that hard-sealed ball valves have been widely promoted.
In fact, the principle of hard sealing gate valve is the same as that of soft sealing, just because it is the seal between metals, the hardness relationship between metals should be taken into account, as well as the working conditions, which medium to go and so on. Generally, hardening is required, and the ball and seat must be ground continuously to seal. Hard-sealed gate valve has a long production cycle and complicated processing, so it is not easy to do a good job of hard-sealed ball valve.
Thirdly, the use conditions are as follows: soft sealing gate valves can generally achieve high sealing, while hard sealing gate valves can be high or low according to requirements; soft sealing needs fire protection, because at high temperature, the material of soft sealing will leak, while hard sealing does not have this problem; hard sealing can generally do a high pressure, soft sealing is not feasible; soft sealing due to the problem of flow media, some fields. It can not be used (for example, some corrosive media); rear hard-sealed valves are generally more expensive than soft-sealed valves. As for manufacturing, there is little difference between them. The main difference is the seat. Soft seals are non-metallic and hard seals are metal.
Fourth, in the selection of equipment: the selection of soft and hard sealing gate valves is mainly based on process media, temperature and pressure. Generally, the medium contains solid particles or has abrasion or temperature higher than 200 degrees. Hard sealing is preferable when the caliber is greater than 50 and the pressure difference of the valve is larger. The opening moment of the valve is also considered. When the moment is larger, the fixed hard sealing gate valves should be selected, regardless of the sealing grade of the soft and hard seals. They can all reach level 6.
