High-pressure valves need to choose different sealing forms and materials according to different pressure levels and working conditions, and a complete valve seal generally includes four aspects:
1. Seat sealing: high-pressure valves generally use metal seals, also known as hard seals, that is, the valve seat and valve plate (closing parts) are metal; However, high-pressure soft seal valves (such as ball valves, plug valves, butterfly valves) are made of non-metallic materials, such as PTFE, NBR, PPL, etc.
2. Stem packing sealing: generally use flexible graphite rings, add stainless steel wires to increase strength, and some valves are made of non-metallic, such as PTFE, RPTFE, NBR, PPL and other materials for sealing in the case of low temperature.
3. Middle seal between the valve body and the bonnet: generally there is a flange structure: with metal winding gasket, metal coated graphite gasket, RTJ metal sealing ring seal. The other is the pressure self-sealing structure (PSB): the spool is made of metal, and the sealing ring is of two types:
One is made of metal + graphite ring material, and the other is made of stainless steel such as F316.
4. Sealing between the valve body and the transfer pipeline: generally there is a flange structure: with metal winding gasket, metal coated graphite gasket, metal RTJ sealing ring sealing; The other is a butt welding structure (BW), that is, the two ends of the valve are welded directly on the pipeline.