A ball valve is a type of quarter-turn valve, using a pivoting ball with a hole. When the ball’s hole lines up with the flow, the valve is open, and when pivoted 90 degrees by the valve handle, the valve is closed.
Because ball valves are adaptable and easy to operate and repair, they are used extensively industrially, and there are several styles of ball valves suitable for varying uses. Valves are generally made of metal or plastic – for example, a PVC or a brass ball valve is very common. Pressure Systems Safety Regulations state that account should be taken of the intended duty of the valve, including the pressure, frequency of use, size, temperature, size and nature of contents when selecting valves.
A Standard Port Ball Valve
With a smaller ball and a correspondingly smaller port, the flow path through the valve is narrower on the inside than on a standard port ball valve, resulting in a flow restriction which produces a pressure drop.
A Full Port Ball Valve
This has an oversized ball which has a hole the same size as the pipeline. This design results in lower friction loss. A full port ball valve is larger and more expensive, but the flow is unrestricted, so this valve is only really used in situations where free flow is required.
Trunnion Ball Valve
The trunnion ball valve has a fixed or supported ball. This means it is suitable for larger and also higher pressure valves.
V Port Ball Valve
A V port ball valve has a ‘v’ shape ball or a ‘v’ shape seat which allows for finer control over opening/closing. The smaller end of the ‘v’ opens first when it starts to open, which allows a stable flow. The design demands a robust construction to deal with the high-velocity fluids, which a standard valve could be damaged by.
For higher temperature or pressures, metal is ideal, and stainless steel or brass ball valves are a suitable choice. A brass ball valve, for example, is noted for its durability and its ability to handle heat.
Engineered plastics offer a useful alternative. The benefits of plastic valves are that they are economical, lighter, offer wider chemical compatibility and are resistant to corrosion.