Butterfly valve with disc type opening and closing a reciprocating swing around 90 ° to open and close or adjusting medium flow of a valve. Butterfly valve is not only simple in structure, small in volume, light in weight, low in material consumption, small in installation size, small in driving torque, easy to operate and fast, but also can have good flow regulation function and closed sealing characteristics, is one of the fastest development of valve varieties in recent decades. Butterfly valves are widely used. The variety and number of its use is still expanding, and to high temperature, high pressure, large diameter, high sealing, long life, excellent regulation characteristics, as well as a valve multi-functional development. Its reliability and other performance indexes have reached a high level.
How to choose the right butterfly valve?
Selecting the right valve for process applications is always tricky because cost is one of the most important drivers. But there are many other factors to consider for proper valve performance. This article will focus on the selection of butterfly valve when some considerations.
Can it withstand stress?
In short, the butterfly valve is one of the most economical valves, but it may not be able to handle certain process conditions, such as high-speed fluid. In this case, a globe valve may be more appropriate.
Butterfly valves are usually the best solution for each flow rate when differential pressure is less than 3 bar (inlet pressure minus outlet pressure). However, for higher differential pressures, consult a valve specialist as these should be reviewed on a case-by-case basis.
When valve closing pressure is considered, butterfly valve closing pressure is usually less than 10 bar. If closing pressure is above this value, butterfly valves need to be carefully considered – in this case, the globe valve can withstand high pressure differential, and butterfly valves may be at risk of unserviceability, seat damage and leakage.
The lining is important
The simple design of the butterfly valve means that the valve can be lined or coated relatively easily. A large portion of the butterfly valve market is occupied by vulcanized rubber valves, which usually prevent corrosion of process fluids. Rubber lining should be limited to 10 bar.
Butterfly valve is typically used for high temperature, and its simple design means that they can be applied to about 1200 ° C high temperature applications, in this case, valve lining refractories.
Low emission application
The rotary motion of the butterfly valve is particularly suited for low emission applications, where the rotary motion of the valve shaft produces less distortion and damages the packing ring, thus the packing usually has a longer life than the equivalent rising stem.
The seat leakage
The requirement to prevent seat leakage is the key to selecting the right butterfly valve. They are produced in a variety of forms, from concentric, double offset (high performance) to triple offset.
Concentric design should be applied regardless of seat leakage. In these designs, the body and disc have interstitial flows. Dual-offset designs are commonly used for control applications. Three – offset design is mainly used for close – closed important isolation applications. The movement of the disc on the triple offset design means that there is little or no contact between the sealing ring and the valve body, so the rotation of the disc does not cause any damage to the seal.
You can save on construction costs
There are no fixed rules for weight and space requirements of the valve; However, butterfly valves usually weigh at least half the weight of a globe valve of the same size. This has the advantage of saving costs during the procurement and construction phases when considering the structure, structural support and handling.
Understand maintenance strategy
One of the main considerations in most butterfly valve designs is that the valve needs to be removed from the pipe for any internal servicing – so it is important to understand the field maintenance strategy before installing the valve.