Butterfly valve, also known as flap valve, is a simple regulating valve, which can also be used for on-off control of low-pressure pipeline medium. Butterfly valve is a kind of valve whose closing part (disc or butterfly plate) is a disc and rotates around the valve axis to open and close. It mainly plays the role of cutting off and throttling in the pipeline. The opening and closing part of butterfly valve is a disc-shaped butterfly plate, which rotates around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjustment. Butterfly valve is applicable to the pipeline conveying various corrosive and non corrosive fluid medium in the engineering system of generator, gas, natural gas, liquefied petroleum gas, city gas, cold and hot air, chemical smelting, power generation and environmental protection. It is used to regulate and cut off the flow of medium.
Application of butterfly valve
Butterfly valve is suitable for flow regulation. As the pressure loss of butterfly valve in pipeline is relatively large, which is about three times of that of gate valve, when selecting butterfly valve, the influence of pressure loss on pipeline system should be fully considered, and the firmness of butterfly plate bearing pipeline medium pressure when closing should also be considered. In addition, the working temperature limit of resilient seat material at high temperature must be considered.
The butterfly valve has the advantages of small structure length and overall height, fast opening and closing speed, and good fluid control characteristics. The structure principle of butterfly valve is most suitable for making large diameter valve. When the butterfly valve is required to control the flow, the most important thing is to choose the size and type of the butterfly valve properly and effectively.
Usually, in throttling, regulating control and mud medium, short structure length and fast opening and closing speed (1 / 4R) are required. Low pressure cut-off (low pressure difference), butterfly valve is recommended.
Butterfly valve can be used in double position adjustment, necking channel, low noise, cavitation and gasification, a small amount of leakage to the atmosphere and abrasive medium.
When using butterfly valve under special working conditions, such as throttling regulation, strict sealing requirement, severe wear, low temperature (cryogenic), etc., special tri eccentric or Bi eccentric butterfly valve with special designed metal sealing device is required.
The mid line butterfly valve is suitable for fresh water, sewage, sea water, brine, steam, natural gas, food, medicine, oil, various acids and bases and other pipelines which require complete sealing, zero leakage in gas test, high service life and working temperature of – 10 ~ 150 ℃.
Soft seal eccentric butterfly valve is suitable for bidirectional opening and closing and adjustment of ventilation and dust removal pipeline. It is widely used in gas pipeline and water channel of metallurgy, light industry, electric power and petrochemical system.
Metal to metal wire sealed 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 face sealed triple eccentric butterfly valve can be widely used in petroleum, petrochemical, chemical, metallurgy, electric power and other fields besides being used as program control valve of large PSA gas separation unit. It is a good substitute for gate valve and stop valve.
Selection principle of butterfly valve
1. Compared with gate valve, butterfly valve has larger pressure loss, so it is suitable for pipeline system with lax pressure loss requirements
2. As the butterfly valve can be used for flow regulation, it is suitable to be selected in the pipeline that needs flow regulation
3. Due to the limitation of butterfly valve structure and sealing material, it is not suitable for high temperature and high pressure pipeline system. Generally, the working temperature is below 300 ℃ and the nominal pressure is below PN40.
4. Because the butterfly valve structure length is relatively short, and can be made into large diameter, so in the case of short structure length requirements or large diameter valve (such as more than DN 1000), butterfly valve should be selected.
5. Because the butterfly valve can be opened or closed only by 90 ° rotation, it is suitable to use butterfly valve in the field where the opening and closing requirements are fast