Author:Site Editor Publish Time: 2018-12-02 Origin:Site
Butterfly valve is a valve that uses a circular disc as a shutter to open, close, and adjust the fluid passage as the stem rotates. The butterfly valve's disc is mounted in the diameter direction of the pipe. In the cylindrical passage of the butterfly valve body, the disc-shaped disc rotates around the axis, and the rotation angle is between 0° and 90°. When the rotation is 90°, the valve is fully open.
1.Butterfly valve design needs
2.The butterfly valve structure
3.Commonly used butterfly valves
Design to make sure that the butterfly valve is used to connect or cut off the medium in the pipeline, or to regulate, control the flow and pressure of the pipeline medium. Different function of the valve when the seal design factor is different, if the valve is used on or off line in the medium, the valve is considered the truncation of ability, namely the sealing performance of the valve, in ensuring that the selected material under the premise of must be corrosion resistant, low and medium voltage and normal temperature often adopt soft sealing structure of valve selection, high temperature and high pressure valve is in the structure of hard sealing; If the valve is used to regulate and control the flow rate and pressure of the pipeline medium, the inherent regulating characteristics and regulating ratio of the valve should be taken into account
Before design, the first to fully understand the process conditions of the valve in the process system, including: medium type (gas, liquid, solid and two-phase or multi-phase mixture, etc.), medium temperature, medium pressure, medium flow rate (or flow rate), power source and its parameters.
Strength and stiffness considerations
Butterfly valve design in addition to the "valve design manual" to provide static design calculation, but also consider the dynamic load due to media pressure, flow rate, etc., especially in the high and medium pressure pipe system when the butterfly valve closed the water hammer energy, but also consider the environmental impact of additional load and pipe, bearing caused by additional load.
The butterfly valve has the characteristics of simple structure, small volume, light weight, material consumption, small installation size, rapid switch, 90° reciprocating rotation, small driving torque, etc. It is used to cut off, connect and adjust the medium in the pipeline. Fluid control characteristics and shut-off sealing performance. When the butterfly valve is in the fully open position, the thickness of the disc is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is small, so it has better flow control characteristics. The butterfly valve has two sealing types: a spring seal and a metal seal. Elastomeric sealing valve, the sealing ring can be mounted on the valve body or attached to the periphery of the disc.
If a butterfly valve is required for flow control, the main choice is the correct size and type of valve. The structural principle of the butterfly valve is especially suitable for making large diameter valves. Butterfly valves are widely used not only in general industries such as petroleum, gas, chemical, and water treatment, but also in cooling water systems for thermal power plants.
Commonly used butterfly valves are clip-on butterfly valves, flanged butterfly valves, and butt-welded butterfly valves. The wafer type butterfly valve uses a stud bolt to connect the valve between the two pipe flanges; the flange type butterfly valve has a flange on the valve, and the two ends of the valve are flanged on the pipe flange; Both ends of the butterfly valve are welded to the pipe.
The streamlined design of the disc makes the fluid resistance loss small, which is an energy-saving product.The valve stem is a through-rod structure. After quenching and tempering treatment, it has good comprehensive mechanical properties, corrosion resistance and scratch resistance. When the butterfly valve is opened and closed, the valve stem only rotates and does not perform lifting operation. The packing of the valve stem is not easy to be broken and the sealing is reliable. It is fixed with the cone pin of the butterfly plate, and the overhanging end is designed to prevent the punch-out type, so as to prevent the valve stem from collapsing when the valve stem and the butterfly plate are accidentally broken.
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