The shape of valve opening and closing parts and valve runner makes the valve have certain flow characteristics. This must be taken into account when selecting valves.
1. Valves for Cutting off and Connecting Media
Valves with small flow resistance and straight flow passage are usually chosen. These valves include gate valves, globe valves and plunger valves. Downward closed valves are seldom used because of the tortuous flow passage and higher flow resistance than other valves. However, closed valves can also be used when high flow resistance is allowed.
2. Valves for flow control
Valves that are easy to regulate flow are usually chosen. For example, control valve, throttle valve, plunger valve, because its seat size is proportional to the travel of the opening and closing parts. Rotary (e.g. cock, ball, butterfly) and flex (pinch, diaphragm) valves can also be used for throttling control, but usually only within a limited valve caliber range. In most cases, people usually change the shape of the globe valve disc for throttling. It should be pointed out that it is extremely unreasonable to change the opening height of gate valve or globe valve to achieve throttling effect. Because the medium in the pipeline is in the throttling state, the flow rate is very high, and the sealing surface is easy to be washed and worn, thus losing the function of cutting off and sealing. Similarly, it is unreasonable to use the throttle valve as the cutting device.
3. Valves for reversing diversion
According to the need of directional diversion, the valve can have three or more channels, suitable for the selection of cock valves and ball valves. Most valves for reversing and diverting use this type of valve. In some cases, other types of valves are properly connected with each other by two or more valves, and can also be used as directional diversion of media.
4. Valves for Medium with Suspended Particles
If the medium has suspended particles, it is most suitable to use its opening and closing parts sliding along the sealing surface with wiping valve. Such as flat gate valve.
