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Butterfly valve selection principles and applicable occasions


Butterfly valve, also called flap valve, is a regulating valve with a simple structure. It can also be used for switching control of low-pressure pipeline media. Butterfly valve refers to a valve whose closing part (valve 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 on the pipeline. The butterfly valve opening and closing part is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment.

Butterfly valves are suitable for regulating and cutting off pipelines transporting various corrosive and non-corrosive fluid media in engineering systems such as generators, coal gas, natural gas, liquefied petroleum gas, city gas, hot and cold air, chemical smelting, power generation and environmental protection. The flow of media.

Butterfly valve is suitable for:

Butterfly valves are suitable for flow regulation. Since the pressure loss of butterfly valves in the pipeline is relatively large, about three times that of gate valves, when selecting butterfly valves, the impact of pressure loss on the pipeline system should be fully considered. The strength of the butterfly plate to withstand the pressure of the pipeline medium when closed should also be considered. sex. In addition, the operating temperature limitations of the elastomeric seat material at elevated temperatures must also be considered.

The structural length and overall height of the butterfly valve are small, the opening and closing speed is fast, and it has good fluid control characteristics. The structural principle of the butterfly valve is most suitable for making large-diameter valves. When a butterfly valve is required to control flow, the most important thing is to correctly select the size and type of butterfly valve so that it can work properly and effectively.

Butterfly valve selection principles

① Usually, in throttling, regulating control and mud media, it is required to have a short structure length and fast opening and closing speed (1/4r). For low pressure cut-off (small pressure difference), butterfly valve is recommended.

② Butterfly valves can be used when there are two-position adjustment, narrowing channels, low noise, cavitation and vaporization phenomena, a small amount of leakage to the atmosphere, and abrasive media.

③ When using butterfly valves for throttling adjustment under special working conditions, or requiring strict sealing, or severe wear, low temperature (cryogenic) and other working conditions, a specially designed triple-eccentric or double-eccentric valve with a metal sealing belt adjustment device must be used. Special butterfly valve.

④ The center line butterfly valve is suitable for fresh water, sewage, sea water, salt water, steam, natural gas, food, medicine, oil and various products that require complete sealing, zero gas test leakage, high life requirements, and an operating temperature of -10~150°C. Acid-base and other pipelines.

⑤ The soft-sealing eccentric butterfly valve is suitable for bidirectional opening, closing and adjustment of ventilation and dust removal pipelines. It is widely used in gas pipelines and waterways in metallurgy, light industry, electric power, petrochemical systems, etc.

⑥ 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, etc., as a regulating and intercepting device.

⑦ In addition to being used as program control valves for large pressure swing adsorption (PSA) gas separation devices, metal-to-metal surface sealed triple eccentric butterfly valves can also be widely used in petroleum, petrochemical, chemical, metallurgy, electric power and other fields. They are gate valves, globe valves, etc. A good alternative product.

Butterfly valve selection principles:

① Since the pressure loss of butterfly valves is larger than that of gate valves and ball valves, they are suitable for pipeline systems with loose pressure loss requirements.

② Since the butterfly valve can be adjusted by flow, it is suitable to be used in pipelines that require flow adjustment.

③ Due to the limitations of the structure and sealing material of the butterfly valve, it is not suitable for use in high temperature and high pressure pipeline systems. The general working temperature is below 300℃, and the nominal pressure is below PN40.

④ Since the butterfly valve has a relatively short structural length and can be made into a large diameter, it is advisable to use a butterfly valve in situations where the structural length is short or for large diameter valves (such as DN1000 or above).

⑤ Since the butterfly valve can be opened or closed by only rotating 90°, it is appropriate to use a butterfly valve in situations where fast opening and closing are required.

Butterfly valve selection principles

Butterfly valve pipeline installation:

① The valve can be installed on the flange only after the flange is welded to the pipe and cooled to ambient temperature. Otherwise, the high temperature generated by welding will affect the performance of the elastic valve seat.

② The edge of the welding flange must be machined with a lathe until the surface is smooth to avoid damaging the elastic valve seat during valve installation. The flange surface must be completely undamaged and deformed, and all dirt, dust and foreign matter must be removed to avoid liquid leakage from the valve and flange interface.

③ Clean the flange and the inner cavity of the pipe to completely remove the spatter, peeling scale and other foreign matter left behind by welding.

④ When installing the valve, set the positioning bolts under the pipe at the same height for support, and adjust the distance between the flanges until the two sides of the valve body are about 6-10 mm apart. Remember that the valve here can only be opened to a 10° position from the closed position.

⑤ Open the valve three times to check whether there is any loose contact between the valve plate and the flange.

⑥ Provide a support for the valve when installing the actuator to avoid distortion of the valve neck and reduce friction between the valve and the pipe.

⑦ Do not step on the valve neck or valve handwheel.

⑧ Do not install DN350 or larger valves upside down.

⑨ Do not install butterfly valves directly on check valves or pumps, as this may cause damage when contacting the valve plate.

⑩ Do not install valves on the downstream side of elbows and reducers, or calibrate valves when the flow rate changes. When this occurs, it is recommended to install the valve at a distance of approximately 10 times the nominal diameter of the valve.

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