A ball valve is a straightforward type of valve – it is a ball with hole in it (hence its name). When the ball is turned so that the hole is inline with the direction of flow then the valve is open. When it is at 90 degrees to the direction of flow it is closed. This describes the ball valve in its simplest form.
Ball valves are very widely used in industry and there are large numbers of manufacturers and suppliers.
Other factors that you might come across with ball valves:
- Most ball valves are hand operated using a lever or tee handle. When the lever or tee handle is at right angles to the valve body it is closed. Turning the handle clockwise turns the valve off.
- An advantage of a ball valve is that you can see at a glance (from the handle position) whether it is on or off.
- Ball valves can be ‘full bore’ or ‘reduced bore’ – this tells you about the through diameter of the valve and hence its flow.
- The ‘DN’ number (e.g. DN15) tells you nominal bore of the valve in mm.
- The ‘PN’ ‘number (e.g. PN40) tells you the pressure rating of the ball valve in bar.
- Ball valves can be lockable – this is normally achieved by a padlock of some kind on the handle which allows you to lock the valve in the closed position – this is used as a safety measure when working on machines etc.
- The female threads on ball valves can be ‘long’ or ‘short’. Be aware that some fittings will have too long a male thread to work with short threaded ball valves. If in doubt chose a ball valve with a long thread.
- Ball valves can also be ‘vented’. This normally applies to valves used on compressed air. When the valve is turned off the air on the downstream side is allowed to escape (slowly) to atmosphere. This is achieved by a small channel being cut in the ball in the right position. In compressed air systems this is often what you want to achieve and vented ball valves should be used much more widely than they are.
Further versions of ball valves include:
- Three way L port or T port
- Actuated valves turned by a pneumatic or electric actuator
- Gas board approvals
- Water board (WRAS) approvals
Ball Valves are a massive subject in its own right but the above is intended as a very rough guide to some of the more basic considerations.