Double eccentric butterfly valve is also called high performance butterfly valve, double eccentric butterfly valve is further improved on the basis of single eccentric butterfly valve. Its structural characteristics are that the axis of the valve stem deviates from the centre of the butterfly plate as well as the centre of the body. The effect of double eccentricity makes the valve to be opened after the butterfly plate can be quickly detached from the valve seat, greatly eliminating the butterfly plate and the seat of the unnecessary excessive pressure, scraping phenomenon, reducing the opening distance, reducing wear and tear, and improving the life of the valve seat. The substantial reduction of scraping also makes it possible to use metal seats for double eccentric butterfly valves, which improves the application of butterfly valves in the field of high temperature.
Compared with concentric disc butterfly valve, double eccentric butterfly valves are more resistant to high pressure, have a longer service life and are more stable. Compared with other valves, the larger the calibre, the lighter the material, the lower the cost. This is the reason why double eccentric butterfly valves are individually known as “high performance butterfly valves“.High performance butterfly valve is a basic product of TWT from Tianjin,China.
What is the double eccentric butterfly valve?
The so-called double eccentricity, the first eccentricity refers to the stem shaft deviation from the centre of the sealing surface, that is, the stem shaft is behind the butterfly plate surface. This eccentricity makes the contact surface of the butterfly plate and valve seat are sealing surface, which fundamentally overcomes the inherent shortcomings of the centre line butterfly valve, thus eliminating the possibility of internal leakage at the upper and lower intersection between the stem shaft and the sealing valve seat.
Another eccentricity refers to the centre of the overwater hole of the valve body and the axis of the valve stem is shifted to the left and right, that is, the axis of the valve stem separates the butterfly plate into two parts of one side and the other side is less. This eccentricity can make the butterfly plate in the opening and closing process can be quickly detached from or close to the valve seat, reduce the friction between the butterfly plate and the sealing seat travel, reduce wear and tear, reduce the opening and closing torque, extend the service life of the valve seat.
Double eccentric butterfly valve’s butterfly plate periphery and sealing seat are processed into hemispherical surface, relying on the outer sphere of the butterfly plate to squeeze the inner sphere of the sealing seat to produce elastic deformation to achieve the purpose of shutting down. The double eccentric butterfly valve usually adopts PTFE material as its sealing seat, and it can also adopt metal sealing seat to expand its application in high temperature field.
However, the sealing of double eccentric butterfly valve with metal sealing seat still belongs to positional sealing structure, i.e. the sealing surface of butterfly plate and valve seat is in line contact, so it is not able to withstand high pressure, which will inevitably lead to a larger leakage when applied in high-pressure system. Therefore, in the high-pressure or the system requiring tight cut-off, the use of double eccentric butterfly valves with metal sealing seat should be avoided as much as possible.
Advantages of high performance butterfly valve
1 Reasonable design, compact structure, easy to install and disassemble, easy to maintain.
2 Eccentric structure reduces the friction of sealing ring and prolongs the service life of the valve.
3 Completely sealed, zero leakage. Can be used in ultra-high vacuum conditions
4 Replacement of the valve plate sealing ring, butterfly plate, shaft and other materials, can be applied to a variety of media and different temperatures.
Wide range of application of high performance butterfly valve
Double Eccentric Butterfly Valve is mainly used in water plant, power plant, steel smelting, chemical industry, water source spring project, environmental facilities construction and other systems for drainage, especially suitable for waterway pipeline, as a regulating and intercepting equipment.
Double eccentric butterfly valves are widely used in chemical systems, such as conveying, mixing, filtration, dehydration and other equipment for media control. In chemical equipment, double eccentric butterfly valve is mainly used to control corrosive media, high temperature media, high pressure media, high viscosity media and solid particles in the medium of flow regulation and cut off control.
- Power equipment
In electric power equipment, double eccentric butterfly valve is mainly used to control the flow and pressure of liquid media. For example, it is used to control the boiler water supply system, turbine inlet and exhaust system, cooling water circulation system and so on.
- Petroleum equipment
In petroleum equipment, double eccentric butterfly valves are mainly used for pipeline systems and storage tanks for media control, such as oil pipelines, refinery equipment, natural gas pipelines, oil and gas storage tanks.
- Food equipment
In food equipment, double eccentric butterfly valve is mainly used to control the flow and pressure of food and beverage. For example, it is used to control beverage production line, washing machine, filling machine and so on.
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