There are various kinds of valves and many complicated working conditions. To choose the most
suitable valves for pipe system, you should know:
First, the characters of valves;
Second, the steps and reasons to select valves;
Third, the principles of choosing valves for oil and chemical industry.
Principles of selecting valves for oil and chemical industry:
1. Straight-flow-channel valves have small resistance and are usually used to stop and open medium;
2. Those which are flexible to adjust flow amount are applied to control the flux;
3. Plug valves and ball valves are suitable for changing direction and dividing the running way;
4. Those valves whose closure parts have wiping ability through sliding along the seal surface are fittest for medium containing particles.
I. Valves for closing and opening medium
Straight-flow-channel valves have small resistance,which are usually used to stop and open medium flow. Close-downward-type valves (
globe valves,
plug valves) are not always been chosen due to their higher flow resistance resulted from their zigzag running ways. They can be used only when high resistance is permitted.
II. Valves for controlling traffic
Generally, valves which can easily adjust the traffic are applied to command flow amount. Close-downward-type valves (globe valves, for example) can be used for controlling, because the size of their seats is in proportion to the moving distance of closure parts. Swing style valves (such as plug valves, butterfly valves and ball valves) and flexible body type valves are also avaiable within limited diameter scope. Gate valves are that discs move transversely along the round seat mouths of valves. They can only control traffic well when closing to closure, so they are seldom been applied to flow control.
III. Valves for chaging the running way of medium
According to the requirements, these valves may have three or more channels. Plug valves and
ball valves are suitable so they are mostly been adapted. However, there are some occasions where other kinds of valves can be used by properly connecting two or more ones with each other.
IV. Valves for medium with particles
It is the most suitable time to use valves whose closure parts have the ability to wipe by sliding along the seal surface when there are particles within the pipe medium. It is likely for the closure parts to nip particles if the closure moves vertically from side to side. Therefore, only when the seal surface allows particles inserting can these kinds of valves be used, otherwise they can only be applied to basically clean medium. Ball valves, plug valves and
butterfly valves have the wiping ability to seal surface when being closed and opened, so they can fit medium contained particles.
At present, in the pipe system whether of oil, chemical or other industries, there are various applications, operation frequency and services of valves. The most crucial equipments for controlling or preventing leakages are valves. Pipelines are finally controlled by valves, whose services and responsible operation in different fields are wonderful.
