Valve

Valve

A valve is a device that regulates, directs, or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure.

Water valves with spigots

Types of Valves

Valves vary widely in form and application. Some of the most common types include:

Ball Valve

A ball valve is a quarter-turn valve that uses a hollow, perforated, and pivoting ball to control flow through it. It is open when the ball's hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle.

Check Valve

A check valve, also known as a non-return valve, allows fluid to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.

Nozzle check valve disc

Gate Valve

A gate valve is a valve that opens by lifting a barrier (gate) out of the path of the fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened.

Globe Valve

A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.

Control Valve

A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level.

Control valve at Gordon Power Station

Valve Components

Valves are composed of several key components:

Body

The body is the main part of the valve that contains the internal parts or trim.

Bonnet

The bonnet is the part of the valve that covers the opening in the body. It is the second most important boundary of a pressure valve.

Trim

The trim is the internal elements of a valve that modulate the flow of fluid. It includes the stem, the seating surface, and other parts that guide the stem.

Actuator

The actuator is a mechanism that moves the valve's modulating element, such as a ball or butterfly, to open or close the valve.

Valve cross-section

Applications

Valves are used in a variety of applications, including:

Industrial

In industrial applications, valves are used to control the flow of gases, liquids, and slurries in a variety of processes.

Household

In household applications, valves are used in plumbing systems to control the flow of water.

Automotive

In automotive applications, valves are used in engines to control the intake and exhaust of gases.

Valve balls

Related Pages

• Fluid dynamics
• Hydraulics
• Pneumatics
• Pipe (fluid conveyance)