Definition, characteristics and classification of butterfly valve

Butterfly valve is a kind of rotary valve that uses a disc-shaped closing member (which can be circular or rectangular, etc.) to turn 90° or about 90° to open and close the valve. Butterfly valve is an ancient valve. In the early days, due to poor sealing performance, it could only be used for adjustment. For example, the flue valve is a kind of regulating butterfly valve. With the emergence of elastic sealing materials such as synthetic rubber, and the in-depth study of sealing mechanisms, sealed butterfly valves have appeared. The emergence of elastic metal valve seats and new structural forms makes butterfly valves gradually adopted in high temperature and low temperature environments. The current development trend of butterfly valves is that they can be used for both adjustment and sealing.

Butterfly valve has the advantages of simple structure, not easy to produce thermal deformation, light weight, small space occupation, relatively small resistance, rapid opening and closing, low opening and closing power, good sealing performance, long life, etc., so it is widely used, especially in low pressure. The application of caliber valves is expanding day by day. In short, sealed butterfly valves are widely used in water systems and gas systems. Such as the water supply and drainage system of municipal engineering, thermal power plant, water supply system, heat pipe network and sewage treatment system, water inlet valve of large turbine of hydropower station, electric power, chemical industry, petroleum, metallurgy, shipbuilding, papermaking, city gas, upper and lower sewers, Butterfly valves have been used in the food industry as well as in atomic energy and national defense projects, and there is a tendency to develop towards high and medium pressure.

The media that the butterfly valve can transport and control include water, condensed water, sewage, seawater and other liquids, air, gas and other gases and steam, dry powder, mud, fruit pulp and mixtures with suspended solids.

The sealing mechanism of the valve is achieved by a certain sealing pressure acting on the sealing surface, and the butterfly valve is no exception. Generally speaking, the sealing of butterfly valve has three forms: 1. The specific pressure is generated by the interference. ②Press the sealing pair tightly by direct pressure or torque, such as double eccentric and triple eccentric butterfly valves, and the sealing ring is filled with liquid. ③ By the Poisson effect, the medium is pressed on the sealing ring, and the greater the pressure difference between the upstream and downstream, the easier it is to seal. Also sometimes utilized are "toggle effect" elastomers where the mid-section of the elastomer is thinner than the outer or inner diameter, and when pressure is applied, the structure allows the outer diameter of the valve seat to flex to seal the contacting surfaces.

Butterfly valves can be classified according to various methods. For example, butterfly valves can be divided into cut-off type and adjustment type according to their purpose and function; they can be divided into midline type, single eccentric, double eccentric and triple eccentric butterfly valves according to their structure; according to sealing materials, It can be divided into rubber sealing butterfly valve, PTFE sealing butterfly valve and metal sealing butterfly valve.