Structure and thermal conductivity of the pneumatic valve component selection:

High temperature and high pressure differential FD-LOK instrument check valve design, it must carefully consider the impact of thermal expansion of the different components of the trim operation. When the high temperature medium flows through the valve, since the coefficient of linear expansion of the valve body is often smaller than the linear expansion coefficient of the valve seat, the valve seat so that the valve body limits the radial expansion of the inner diameter of the expansion valve can only, at a high temperature so that the valve working gap between the core and the valve seat is less than the gap between the standard design at room temperature, resulting trim stuck. Spool and the guide sleeve will produce the same phenomenon. Thus, when the valve used in high temperature, room temperature design space standard valves (including inter-valve, valve seat; guide sleeve, between the stem) should be appropriately increased, so that it will not work stuck phenomenon occurs at high temperatures . Therefore, the gap design is very important because confirm material, size and temperature parameters on poor design staff is very important, at present, the corresponding data can be obtained from "ASME Boiler and Pressure Vessel Code Material D Part Ⅱ Performance" in.
Request a higher amount of leakage occasions valve and valve seat as far as possible the same alloy steel, and a single seat or cage structure, try to avoid using the valve seat structure, but also in the sealing surface hardening process, so as to avoid high temperature dramatically increasing the amount of valve leakage. It should also consider the body, bonnet and connectors withstand damage caused due to the additional load caused by high temperatures.
Cyclic changes in temperature cause the seat and the guide sleeve is loose, it must be sealed lap welding and welding to locking or clamping structure. Seat gasket seal is greater than the yield limit gasket sealing force to be able to get, but at a high temperature, high pressure and thermal cycling conditions, the sealing material creep arising from leakage, the seat can be used as a whole, by a valve made directly on the body and hardened valve seat. For large diameter valves, welding seat on the body, removing shims to avoid unnecessary leaks. Depending on the temperature level of the medium, but also consider the stuffing box packing can withstand temperatures and actuators can withstand temperatures.