Valves are the components in a fluid flow or pressure system that regulate either the flow or the pressure of the fluid. They are used extensively in the process industries, especially petrochemical. Valves and actuators are widely used across industry and this dedicated reference provides all the information plant designers, specifiers or those involved with maintenance required. Industries that use pumps, seals and pipes will also use valves and actuators in their systems. This key provides anyone who designs, uses, specifies or maintains valves and valve systems with all of the critical design, specification, performance and operational information. In the presentations in their chapters, authors have written bases on their own experience as well as those of their associates. Most chapters overlap several others. If differences of opinion or technique become apparent, seeming contradictions, it is because each author has had success with his or her particular technique, not that others are wrong. It should be recognised that each author's experience may not be directed to a particular industry, perhaps omitting ideas important to other industries. An effort has been made to cross-reference chapters so that the reader may be aware of other points of view.