Valves are one of the most important components for a pipeline or piping system, because valves enable process engineers to open, close, and redirect the flow, control the flow rate, adjust the pressure of the system, release pressure, and more. Based on functions, working conditions (including type of media, flow rate, pressure, and temperature) and other requirements, proper valves need to be selected for each specific application.
In general, the valve body, bonnet or cover, and body joint, bolting shall be constructed of material as listed in the respective ASTM specifications referred to in Table 1 of the ASME code B16.34.1 Materials for different services proposed in this standard come from real world experience including failures and successes, therefore are tested and proven.