Selection of Valves - Flow Characteristics and Connection Forms


Published:

2023-01-16

When selecting valves, it is first necessary to grasp the performance and flow characteristics of the medium, as well as the performance of temperature, pressure, flow rate, and flow rate. Then, combined with factors such as process, operation, and safety, corresponding types, structural forms, and model specifications of valves should be selected.

When selecting valves, it is first necessary to grasp the performance and flow characteristics of the medium, as well as the performance of temperature, pressure, flow rate, and flow rate. Then, combined with factors such as process, operation, and safety, corresponding types, structural forms, and model specifications of valves should be selected.
Select valves based on flow characteristics
The shape of the valve opening and closing parts and the valve flow channel endow the valve with certain flow characteristics. When selecting valves, this must be taken into account.
(1) Valves for cutting off and connecting media
Usually, valves with small flow resistance and straight through flow channels are chosen. These types of valves include gate valves, globe valves, and plunger valves. Downward closed valves are less commonly used due to their tortuous flow paths and higher flow resistance compared to other valves. However, in situations where high flow resistance is allowed, closed valves can also be used.
(2) Valves for controlling flow
Usually, valves that are easy to adjust flow are chosen. For example, regulating valves, throttle valves, and plunger valves, their seat size is directly proportional to the stroke of the actuator. Rotary (such as plug valves, ball valves, butterfly valves) and flexible (clamp valves, diaphragm valves) valves can also be used for throttling control, but are usually only applicable within a limited valve diameter range. In most cases, people usually use changing the disc shape of the shut-off valve for throttling purposes. It should be pointed out that changing the opening height of a gate or globe valve to achieve throttling effect is extremely unreasonable. Because the medium in the pipeline is in a throttling state, the flow rate is high, and the sealing surface is prone to erosion and wear, losing the sealing effect of cutting off. Similarly, using a throttling valve as a cutting device is also unreasonable
(3) Valve for reversing and diverting
According to the needs of directional diversion, this valve can have two or more channels, suitable for selecting plug valves and ball valves. Most of the valves used for reversing and diverting use this type of valve. In some cases, other types of valves can also be used as directional diverters for media by connecting two or more valves to each other appropriately.
(4) Valves for media with suspended particles
If the medium contains suspended particles, it is most suitable to use a valve with a wiping effect when the opening and closing parts slide along the sealing surface, such as a flat gate valve.