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, select the corresponding type, structure form, model specifications of the valve.

1 Select valve according to flow characteristic

Valve opening and closing parts and valve flow of the shape of the valve with a certain flow characteristics. This must be taken into account when selecting valves.

(1) Disconnect and connect the medium valve

Usually select a small flow resistance, flow channel for the straight-through valve. This kind of valve has the gate valve, the globe valve, the plunger valve. Downward closed type valve, because the flow path twists and turns, the flow resistance is higher than other valves, so less choice. However, closed-type valves can also be used in occasions where high flow resistance is allowed.

(2) Control flow valve

Usually select the valve that is easy to adjust the flow. such as regulating valve, throttle valve, plunger valve, because its seat size and the starting firmware of the trip into a proportional relationship. Rotary (such as plug valve, ball valve, butterfly valve) and the flexible form (pinch valve, diaphragm valve) valve can also be used for throttling control, but usually only within the limited range of valve caliber. In most cases, it is commonly used to change the disc shape of the globe valve to make throttling. It should be pointed out that it is extremely unreasonable to use the opening height of the gate valve or globe valves to achieve throttling effect. Because, in the pipeline medium in the throttling state, the flow rate is very high, the seal surface is easy to be washed and worn, loses the sealing effect, similarly, uses the throttle valve as the cut-off device is also unreasonable.

(3) Reversing shunt valve

According to the need of commutation shunt, this valve can have two or more channels, suitable for selecting plug valve and ball valve. Most of the valves used for directional diversion are selected for this type of valve. In some cases, other types of valves, with two or more only properly connected to each other, can also be used as a commutation shunt for the medium.

(4) Valves with suspended particles

If the media with suspended particles, the most suitable for the use of its headstock along the sealing surface of the sliding with the wiping action of the valve, such as flat gate valve.