Valve Closure Members: Types, Functions, and Selection Criteria

A valve closure member is a movable component that opens or closes a flow passage to regulate or stop fluid flow. Actuated by manual levers, springs, or actuators, materials vary by application. Common types:

1. Disc

Flat or round element moving perpendicular to flow. Used in ball, butterfly, and diaphragm valves.

2. Ball

Spherical element that seals by rotating. Quarter-turn operation.

3. Gate

Wedge-shaped element moving linearly across flow path. Used for full-bore flow control.

4. Plug

Cylindrical or tapered element turned or inserted into the body. Good sealing for abrasive or viscous fluids.

5. Diaphragm

Flexible membrane that flexes to control flow. No precise seal between moving parts; suitable for corrosive or high-purity applications.

6. Flapper

Hinged element that swings to open/close. Common in check valves to prevent backflow.

Selection depends on valve type, pressure rating, temperature range, fluid compatibility, and desired flow characteristics.