Select the valve first to master the performance of the media, flow characteristics, as well as temperature, pressure, flow rate, flow and other properties, and then, combined with the process, operation, safety factors, choose the corresponding type, structure form, model specifications of the valve.

1 Choose the valve according to the flow characteristic

Valve opening and closing parts and valve flow path shape so that the valve has a certain flow characteristics. This must be taken into account when selecting valves.

(1) cut-off and connected with the media valve

Usually choose the flow resistance is small, flow channel for straight-through valve. Such valves have gate valves, globe valves, plunger valves. The downward closed type valve, because the flow path twists and turns, the flow resistance is higher than other valves, therefore is few chooses. However, closed-type valves can also be used in cases where high flow resistance is permitted.

(2) control the flow of the valve

Usually choose valves that are easy to adjust the flow. such as the control valve, throttle valve, plunger valve, because its seat size and the start of the firmware of the stroke is proportional relationship. Rotary type (such as plug valve, ball valve, butterfly valve) and flexible form (pinch valve, diaphragm valve) valve can also be used for throttling control, but usually only in the limited range of valve diameter applicable. In most cases, the valve shape of the cut-off valve is usually used for throttling. It should be pointed out that it is unreasonable to change the opening height of valve or cut-off valve to achieve throttling effect. Because, in the pipeline medium in the throttling state, the flow rate is very high, the sealing surface is apt to scour wears, loses shuts off the sealing function, similarly, uses the throttle valve as the cut-off device is also unreasonable.

(3) Reversing shunt valve

The valve can have two or more channels, suitable for use with plug valves and ball valves. This type of valve is used for most directional diversion valves. In some cases, other types of valves, with two or more are only properly connected to each other, can also be used as the medium of commutation diversion.

(4) Valves with suspended particles

If the medium with suspended particles, the most suitable for the opening and closing parts along the sealing surface of the sliding with the role of wiping the valve, such as flat gate valve.