From Valve Selection Handbook: Engineering Fundamentals for Selecting the Right Valve Design for Every Industrial Flow Application, Fifth Edition

OVERVIEW

The purpose of this book is to assist the Piping Specifying Engineer in the selection of valves for a specific application and that meet the design parameters of the process service. Valve selection is based on function, material suitability, design pressure/temperature extremities, plant life, end connections, operation, weight, availability, maintenance, and cost. I have deliberately placed cost at the end for a reason. If the valve does not meet the design criteria, then even if it is free, it is still too expensive, because of the costs to replace it when it fails. Just like life, valve selection is a series of compromises.

Valves are the components in a fluid flow or pressure system that regulate either the flow or the pressure of the fluid. This duty may involve stopping and starting flow, controlling flow rate, diverting flow, preventing back flow, controlling pressure, or relieving pressure.

These duties are performed by adjusting the position of the closure member in the valve. This may be done either manually or automatically. Manual operation also includes the operation of the valve by means of a manually controlled power operator. The valves discussed here are manually operated valves for stopping and starting flow, controlling flow rate, and diverting flow; and automatically operated valves for preventing back flow and relieving pressure. The manually operated valves are referred to as manual valves, while valves for the prevention of back flow and the relief of pressure are referred to as check valves and pressure relief valves,...

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Products & Services
Air Valves
Air valves allow metered fluid flow in one or both directions. They are used in pneumatic circuits to regulate the rate of activation or exhaust of cylinders and other pneumatic devices.
Water Valves
Water valves are designed to handle and control hot water, cold water, ground water, potable water, salt water and/or wastewater. They are made from metal or plastic.
Industrial Valves
Industrial valves are classified in many different ways. They can be distinguished by material of construction, media handled, and/or application.
Butterfly Valves
Butterfly valves control flow through a circular disc or vane by turning the valve's pivot axis at right angles to the direction of flow in the pipe. They are normally used as throttling valves to control flow.
Globe Valves
Globe valves are linear motion valves with rounded bodies, from which their name is derived.  They are widely used in industry to regulate fluid flow in both on/off and throttling service. 

Topics of Interest

The fundamentals of a particular type of valve relate to its sealing characteristics, which include in-line seat sealing when closed and where applicable stem sealing which should prevent potential...

FUNCTIONS OF MANUAL VALVES A manual valve is considered to be a valve that is operated by plant personnel directly, by the use of either a handwheel/wrench or an on/off actuator in the case of...

SELECTION OF VALVES The method by which the closure member regulates the flow and the configuration of the flow path through the valve impart a certain flow characteristic to the valve, which is...

11.1 TYPES OF VALVES All devices considered in this chapter, even those called controls, are valves in that they are placed in refrigerant lines and can restrict or even completley block the flow of...

Valves are essential elements for controlling fluid system performance. Virtually every fluid-power system requires some type of valve. In a hydraulic system, valves may control pressure, flow to an...