What is the difference between valve soft seal and hard seal? How to choose?

1. In terms of structure and mechanism, the hard seal valve is a seal between metal and metal. The sealing surface and valve seat are all metal, and the machining accuracy and process are difficult. Generally, it is used in high pressure, usually above 2.5MPa. Soft seal is the seal between metal and non-metal, such as nylon \ tetrafluoroethylene, the manufacturing standard is the same.
2. The soft and hard seal on the sealing material refers to the sealing material of the valve seat. The hard seal is precision machined with the valve seat material to ensure the matching accuracy with the valve core (ball), generally stainless steel and copper. Soft seal means that the sealing material embedded on the valve seat is a non-metallic material. Because the soft sealing material has a certain elasticity, the machining accuracy requirements are lower than that of the hard sealing.
3. In the manufacturing process, due to the complex working environment of many chemical and mechanical industries, many of which are high temperature and high pressure, the friction resistance of the medium is large, and the corrosion is strong. Now the technology has advanced, the use of various materials is better, and the processing And other aspects can keep up, so that the hard seal valve has been widely promoted. In fact, the principle of the hard seal valve is the same as that of the soft seal, but because it is a seal between metals, the hardness relationship between the metals, as well as the working conditions and the medium used, must be considered. Hardening treatment is generally required, and continuous grinding between the sealing surfaces is required to achieve sealing. Hard sealing valves have a long production cycle and complex processing, which is not easy.
4. In terms of use conditions, soft-sealed valves can generally achieve high sealing, while hard-sealed valves can be high or low according to requirements; soft-sealing needs to be fireproof, because at high temperatures, the material of soft-sealing will leak, while hard-sealed valves will leak. There is no such problem; hard seals can generally do very high pressures, but soft seals cannot; soft seals cannot be used in some occasions (such as some corrosive media) due to the problem of the flowing medium; Soft seals are expensive. As for manufacturing, there is little difference between the two, mainly the difference between the valve seat, the soft seal is non-metallic, and the hard seal is metal.
5. In the selection of equipment, the selection of soft and hard sealing valves is mainly based on the process medium, temperature and pressure. Generally, the medium contains solid particles or has wear or the temperature is higher than 200 degrees. It is best to use hard sealing. If the torque is large, the opening torque of the valve should also be considered. When the torque is large, a hard-sealed valve should be selected. How to choose soft sealing and hard sealing area of valve?
1. Soft seal In addition to the corrosion-resistant lining valve, the general soft seal valve refers to a valve in which either the valve core or the valve seat adopts a non-metallic material (mainly polytetrafluoroethylene, and rubber, etc.) in the form of sealing. The soft sealing valve has the best sealing effect, but more or less unclean debris (such as welding slag, iron filings, etc.) may be left in the pipeline installation and system cleaning. The soft sealing valve seat or valve core is scratched, which increases the leakage and causes poor sealing reliability. Therefore, the selection of the soft sealing structure must consider the cleaning of the medium and the strict flushing of the pipeline before putting into operation.
2. Hard sealing and hard sealing and then surfacing wear-resistant alloys are the best choices for shut-off valves. In this way, the service life and reliability are also considered while considering the sealing performance. Although the factory index is only 10-6 to 10-8, which cannot achieve the effect of zero leakage of the soft seal, it is enough to meet the requirements of strict shut-off, and it Durable and more cost-effective from an economical point of view. Content from the Internet