In pipeline system, valves are control elements used for isolating equipments from pipelines, regulating flow, preventing backflow, regulating and relieving pressure. Choosing the most suitable valves for pipeline system is important. So the characteristics and the principles for valves selection also play important roles. 

 

Principles for valves selection:

1. Valves used for cutting off or connecting media. The passages of valves which are used for cutting-off or connecting media is straight-way. The valves having low fluid resistance are general used for cutting-off or connecting. Downward closed valves such as globe valves and plunger valves are used less for their zigzag passageway and higher fluid resistance than that of other types of valves. For the institution having high fluid resistance, closed valves can be used. 

 

2. Valves used for regulating flow. Valves apt to control flow are used for regulating flow. Downward closed valves are quit suitable. Because of dimension of seat has positive relationship with stroke of closure components. Swing valves (plug valves, butterfly valves, ball valves) and bend valves (pinch valves and diaphragm valves) can be also used for throttling. However, they are only used inside limited nominal diameter scope. The disc plate of gate valves transects with round seat mouth. Gate valves can only control flow well when valves almost turning off. For this, gate valves are not used for regulating flow. 

 

3. Valves used for reversing diffluence. For reversing diffluence, the valves should have three or more passageways. Both plug valves and ball valves are fit for reversing diffluence. So most of valves used for reversing diffluence are chosen from plug valves or ball valves. However, for other types of valves, two or more valves which are connected with each other properly can be also used for reversing diffluence.