Selection and Application of the Butterfly Valve
Butterfly valve is a simple regulating valve that can also be used for the purpose of switch control of low-pressure pipelines and mediums. Butterfly valve is a valve with a disc shaped closure part (valve plate) which can open and close around the valve shaft. It mainly plays the role of cutting off and throttling on the pipeline. Butterfly valve opening and closing part is a disc shaped butterfly plate that rotates around its axis in the valve body to achieve the opening, closing or adjusting functions of the pipe. Butterfly valve is suitable for the pipeline conveying various corrosive and non-corrosive fluid mediums in the generator, gas, natural gas, liquefied petroleum gas, urban gas, cold and hot air, chemical smelting and power generation environmental protection system. It is used to regulate and cut off the flow of the medium.
Butterfly Valves Application
Butterfly valve is suitable for the flow regulation activities. Since the pressure loss of the butterfly valve in a pipeline is relatively large, it is about three times of a gate valve. Therefore, when selecting a butterfly valve the influence of pressure loss on the pipeline system should be fully considered. The valve plate should also be considered when performing the closing activities to bear the pipeline medium pressure. In addition, the limit of the operating temperature of the elastic seat material at high temperatures must be considered as well.
The structure length and overall height of the butterfly valves are small. The opening and closing speed is fast and it has good fluid control characteristics. The structure principle of the butterfly valve is most suitable for making a large caliber valve. When the butterfly valve is required to be used for controlling a flow, it is important to select the correct size and type of a butterfly valve to achieve proper work and efficiency.
Generally, in the throttling, regulating control and mud medium aspects, the structure length is short and the opening and closing speed is fast. Therefore, a low pressure cut-off butterfly valve is recommended.
A butterfly valve can be selected for the task at hand in case of a double position adjustment, the channel of the shrinkage port, low noise, cavitation and gasification, a small amount of leakage to the atmosphere and abrasive medium.
When using a butterfly valve under special conditions such as throttling regulation, strict sealing or severe wear, low temperature (deep cooling) and other working conditions, special butterfly valve with special design metal seal belt regulating device shall be used.
The central butterfly valve is suitable for fresh water, sewage, sea water, salt water, steam, natural gas, food, medicine, oil, acid and alkali and other pipelines with the requirements of full sealing, zero gas test leakage, high service life and operating temperature of -10-150 ℃.
The soft seal eccentric butterfly valve is suitable for the two-way opening and closing of the ventilation and dust removal pipeline. It is widely used in the gas pipeline and water channel of metallurgy, light industry, power and petrochemical system.
Metal to metal double eccentric butterfly valve is suitable for urban heating, steam supply, water supply and gas, oil, acid and alkali pipelines as regulating and intercepting devices.
Metal to metal sealing three eccentric butterfly valve is not only a program control valve for PSA gas separation device, but also widely used in petroleum, petrochemical, chemical, metallurgy, power and other fields and is a good substitute for the gate valve and stop valve.
Selection Principle of a Butterfly Valve
Because butterfly valves are relatively large compared to gate valves, they are suitable for pipeline systems with less pressure loss requirements.
Since butterfly valves can be adjusted by flow, they are suitable for selection in the pipeline requiring flow regulation.
Due to the limitation of butterfly valves’ structure and sealing material, they are not suitable for high temperature and high pressure pipeline system. The general working temperature is below 300 ℃ and the nominal pressure is below PN40.
The butterfly valve has a short structure length and can be made of large diameter. It is therefore advisable to select a butterfly valve for the case of short structure length or large diameter valve (such as over DN1000).
The butterfly valve rotates at 90 ° and can therefore be opened or closed and is suitable for the field with fast opening and closing requirements.