Although all valves have the same basic components and function to control flow in some
fashion, the method of controlling the flow can vary dramatically. In general, there are four methods of controlling flow through a valve.
- Move a disc, or plug into or against an orifice (for example, globe or needle type valve).
- Slide a flat, cylindrical, or spherical surface across an orifice (for example, gate and plug valves).
- Rotate a disc or ellipse about a shaft extending across the diameter of an orifice (for example, a butterfly or ball valve).
- Move a flexible material into the flow passage (for example, diaphragm and pinch valves).