OVERVIEW

Valves are essential components of a piping system, and they allow the process fluid to be controlled and directed on its journey through the process plant. They are expensive engineered items, and it is important that the correct valve is specified for the function and that it is constructed of the correct material for the process fluid.

There are two methods of operating a valve: manually, with a handwheel, lever, wrench, or actuator; or through automatically controlled valves. The piping material engineer is responsible for specifying and requisitioning valves of the first group; however, the second group are tagged valves, and they are generally the responsibility of the instrument engineer.

Table 7.1 shows the various types of valves available for specific functions. This is a basic guide. Once the type of valve has been selected, the design can be finalized, design codes referenced, and the materials of construction chosen.