This Recommended Practice addresses the special needs of control valve applications in refinery services. The knowledge and experience of the industry has been captured to provide proven solutions to well-known problems. 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, and discusses control valve sizing, noise, and fugitive emissions as well as defining 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, and special design valves for refinery services, such as FCCU slide valves and vapor depressuring systems, are also included in this Recommended Practice.