Differences Between Soft Seal & Metallic Seal of Gate Valves
1. In Terms of Structure
The metallic seal is a metal-to-metal seal, where both the sealing ball and seat are metal. Its machining accuracy and technology is relatively difficult, and it is generally used in high pressure - 35MPa or above. Soft seal is the seal between metal and non-metal, such as nylon and tetrafluoroethylene.
2. In Terms of Sealing Materials
The metallic seal is to precisely machine the seat material. To ensure the accuracy of the fit with the spool (ball), stainless steel and copper are the most common copper. Soft seal means that the sealing material inlaid on the valve seat is non-metallic material. Because the sealing materials are somehow flexible, the requirements upon machining accuracy is relatively lower.
3. In Terms of Conditions of Use
Soft seals can generally reach a very high level, while that of hard seals can be high or low depending on requirements. Soft seals need to be fireproof, because at high temperatures, leakage will happen to soft seal materials, while hard seals do not have this problem. Hard seals can generally be made to very high pressures, while soft seals cannot. Soft seals cannot be used in corrosive media. Finally, hard-sealed valves are generally more expensive than soft-sealed ones. As for the manufacturing aspect, there is little difference between the two, mainly the difference in the valve seat.
4. In the equipment selection
In general, when the medium contains solid particles or the temperature is higher than 200 degrees, the best choice is a metallic seal valve. The torque required to open the valve should also be taken into consideration: when the torque is large, a hard seal should be selected.
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