This document provides recommended criteria for the selection, specification and application of piston and diaphragm actuated control valves. It also outlines control valve design considerations, discusses control valve sizing, noise, fugitive emissions, and defines types of commonly used control valves and their actuators. Recommendations for emergency block and vent valves, on/off valves intended for emergency isolation or venting, a special design valves for refinery services, such as FCCU slide valves and vapor depressuring systems, are included.