Rigid seal and soft seal
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What do hard sealing and soft sealing of valves refer to, and which part of the valve do they relate to? ? ?
Hard sealing and soft sealing of valves refer to the sealing surfaces of the valve; when rubber is used to cover the sealing area of the valve, or when rubber-sealed elements are incorporated into the valve body, this is referred to as soft sealing； When additional metal rings or cemented carbide seals are inserted at the valve’s sealing area, it is called a hard seal. The leakage rating for soft seals can reach level 6, while that for hard seals is 5. Due to the special properties of its sealing material, hard seals exhibit good performance at high temperatures; in contrast, the sealing material used in soft seals tends to age easily when exposed to high temperatures
The valve’s sealing surfaces are located in two places: the static seal and the dynamic seal. The dynamic seal refers to the part related to the valve stem; it is usually a multi-stage seal, and in most cases it is a soft seal, composed of materials such as polytetrafluoroethylene, O-rings, wedge seals, stone grinder seals, and bellows. The static seal refers to the sealing surface of the valve seat, the part that comes into contact with the valve core. As mentioned earlier, for metal triple-eccentric butterfly valves, hard seals can achieve six stages of sealing, although they are very expensive, and not many manufacturers are capable of producing them
Besides metal seals, what other types of hard seals exist? I’ve also heard of hard and soft seals – what do those refer to? What materials are generally used for soft seals?
Soft-sealing materials are generally made of rubber or polytetrafluoroethylene. Soft-seal and hard-seal refer to a configuration in which both metal and a soft-sealing material are present at the sealing surface; I’m not entirely sure about the specific applications for this approach. 4# monkeyyd
Design institutes often opt for soft seals, as they are inexpensive and offer a high level of sealing performance. However, soft seals should be used with caution in the field, as the media there often contain impurities; even media that are supposed to be very clean can occasionally become dirty. And even if they aren’t dirty, does that mean there’s no need for purging? The soft seal can only be purged for 5 minutes. So, although it is expensive and its sealing rating is generally not high, a hard seal is usually required.
Great post; I’ve learned something from it. It seems that both butterfly valves and gate valves in use there employ soft seals, with no hard seals being used.
Agree with what was said on the 2nd floor; soft seals are used mainly because they provide good sealing and prevent leaks
Hard seal and soft seal refer to the sealing surfaces of the valve
Please explain why soft-sealed valves can only be purged for 5 minutes
Medium: Diesel, at normal temperature and 0.9 MPa. What is the difference between soft-seal and hard-seal valves? In terms of service life and cost-performance.