Valve base introduction and function. The valve base is a detachable face part in the valve, which is used to support the fully closed position of the spool and constitute a sealing pair. General valve seat diameter is the maximum flow diameter of the valve. For example, butterfly valve seat material is very wide, all kinds of rubber, plastic, metal materials can be used as seat material, such as: EPDM, NBR, NR, PTFE, PEEK, PFA, SS315, STELLITE and so on.
The valve base uses an elastic sealing material and small actuator thrust to achieve a bubble grade seal. The compression seat sealing stress causes the material to elastomically deform and squeeze into the rough surface of the metal parts used to block all leakage pathways. The permeability of the material is the basis for small leakage of the fluid.
Materials that are too soft, or exhibit cold deformation (creep) under load, can be hardened with fillers such as glass fibers. If used to make thin sheets, still can meet the requirements of use, can eliminate cold deformation or permanent deformation.
The seal must be carefully fixed to prevent rupture and leakage due to the effect of differential pressure. Soft seat bonding to metal parts is one way, but is not a complete solution, because the bond will crack and fail when subjected to thermal shock. A sufficiently large depressurization will destroy the bonding material.
Material property editing
The material properties of soft valve seat should be considered
1) Fluid compatibility, including expansion, hardness loss, permeability, degradation;
2) Hardness;
3) permanent deformation;
4) Recovery degree after load elimination;
5) tensile strength and compression strength;
6) Deformation before rupture;
7) Elastic modulus.
