How to choose the valve according to the flow characteristics

Update:19-01-2019
Summary:

The shape of the valve opening and closing member and t […]

The shape of the valve opening and closing member and the valve flow passage allows the valve to have a certain flow characteristic. This must be taken into consideration when selecting a valve.

1. Cut and close the valve for the medium

Valves with a small flow resistance and a straight-through flow are usually selected. Such valves have gate valves, globe valves, and plunger valves. The downwardly closed valve is less used because the flow path is tortuous and the flow resistance is higher than other valves. However, closed valves are also available where higher flow resistance is permitted.

2. Valves for controlling flow

Valves that are easy to adjust flow are usually selected. Such as regulating valve, throttle valve, plunger valve, because its seat size is proportional to the stroke of the opening and closing member. Rotary (eg, plug valves, ball valves, butterfly valves) and flexing valve bodies (pinch valves, diaphragm valves) valves can also be used for throttling control, but are usually only available in a limited range of valve sizes. In most cases, it is common to use a valve flap shape that changes the shutoff valve for throttling. It should be noted that it is extremely unreasonable to change the opening height of the gate valve or the shut-off valve to achieve the throttling effect. Because the medium in the pipeline is in a throttling state, the flow rate is high, the sealing surface is easily washed and worn, and the sealing function is lost. Similarly, it is unreasonable to use the throttle valve as the cutting device.

3. Reversing diverting valve

Depending on the commutation split, this valve can have three or more passages and is suitable for use with plug valves and ball valves. Most valves for commutating splits use this type of valve. In some cases, other types of valves, which are suitably interconnected with two or more, can also be used as a commutating split for the medium.

4. Valves for media with suspended particles

If the medium has suspended particles, it is most suitable to use a valve with a wiping action of its opening and closing member along the sealing surface. Such as slab gate valves.