Valve

Valves come in various forms; the question is too general. Generally, there are dynamic sealing points between the valve stem and the valve body, dynamic sealing at the valve port, static sealing to connect the valve, and in some cases, static sealing at the end of the valve stem. It’s better to be more specific.

Well, that’s too general. Main shaft seal, gland seal.

The sealing points of various valves vary; they can generally be divided into internal sealing and external sealing. Internal sealing refers to the sealing at the upstream and downstream areas, such as at the valve disc or valve plate. When internal sealing fails, internal leakage occurs – that is, when the valve is closed, material from the upstream side can leak to the downstream side, but it does not leak outside. This can affect the accuracy of process control, but it does not result in any loss of material or pose a safety risk. However, for materials whose properties are significantly affected by reactions, internal leakage in the valve can still be harmful. In situations where it is necessary to stop a reaction or keep it within certain limits, internal leakage in the valve may cause the reaction to get out of control or deviate from the desired range of control. External sealing refers to the sealing between the inside and outside of the valve, as well as between the inside and outside of the pipeline, such as at the valve stem or at the two halves of a two-way valve body. Leaks at such seals can lead to the leakage of materials, posing safety risks or causing waste due to the loss of those materials.

For materials with strict requirements regarding internal leakage, such as those that are toxic or harmful, flammable or explosive, or those with a high saturated vapor pressure, it is possible to install dual valves at the base of the container, or two valves at the point where manual control is applied. Of course, pneumatic or electric control valves can be supplemented with upstream and downstream shut-off valves for temporary adjustments; these shut-off valves can be replaced or repaired after making the necessary adjustments. For applications where strict requirements are imposed on leakage prevention, such as those involving toxic or hazardous substances, or flammable and explosive materials, zero-leakage valves with valve stems equipped with metal bellows seals can be used; for substances like carbon monoxide, it is best to opt for imported valves.

Different valve structures have different sealing points.

Different valves have different sealing points, generally including internal and external seals