A butterfly valve is a type of valve used to open, close or regulate the flow of a medium by reciprocating and rotating a disc-shaped component by about 90 degrees. The butterfly valve is not only simple in structure, small in size, light in weight, economical in materials, small in installation size, requires low driving torque, is easy to operate, and quick, but also has good flow control function and closure sealing characteristics. It is one of the fastest developing valve varieties in the past decade in wholesale butterfly valve. Butterfly valves are widely used. The variety and quantity of its usage are still expanding and developing towards high temperature, high pressure, large diameter, high sealing, long service life, excellent regulating characteristics and multi-functional features. Its reliability and other performance indicators have reached a high level.
Butterfly valves have the characteristics of a simple structure, small size, light weight, low material consumption, small installation size, fast opening and closing, 90-degree reciprocating rotation, and low driving torque, which are used to cut off, connect and regulate the medium in the pipeline. They have good fluid control characteristics and sealing performance.
The butterfly valve can transport mud, and the least amount of liquid is accumulated at the pipe mouth. It can achieve good sealing under low pressure and has excellent regulating performance.
The streamline design of the butterfly plate reduces fluid resistance loss and can be called an energy-saving product.
The valve stem adopts a through-rod structure, which has good comprehensive mechanical properties, corrosion resistance and scratch resistance after quenching and tempering. When the butterfly valve is opened or closed, the valve stem only rotates and does not move up and down. The valve stem packing is not easy to damage, and the sealing is reliable. It is fixed with a tapered pin with the butterfly plate, and the extended end is designed to prevent the valve stem from bursting in case of accidental rupture of the valve stem connected with the butterfly plate.
The connection methods include flange connection, clamp connection, butt-welded connection and lug clamp connection. The driving forms include manual, turbine driving, electric, pneumatic, hydraulic, and electro-hydraulic linkage actuators, and can achieve remote control and automatic operation.
Structurally, the closed part (butterfly plate) of the butterfly valve is in the middle of the medium. When designing, its influence on flow resistance should be considered. Its thickness should not be greater than 2.25 times the diameter of the valve stem. One foreign company reduced flow resistance by making the butterfly plate into a shape of an iron cake. Some companies make the small butterfly valve plates very thin.
The rubber sealing ring of the rubber butterfly valve has a short service life, which is related to the quality of the rubber and the width of the sealing surface. The vulcanization temperature should not be arbitrarily increased, and the time should not be shortened, otherwise the sealing ring is prone to aging and cracking. The metal sealing face that matches the rubber sealing ring should have a sufficient width, otherwise, the rubber sealing ring is not easy to embed. In addition, the shape and position tolerances, symmetry, accuracy, smoothness of the valve body and butterfly plate, and the compression and elasticity of the sealing ring also affect the service life of the rubber sealing ring.
Stiffness is an important issue in the design of butterfly valves, which is related to the butterfly plate, valve shaft, and connection. If the size of the valve shaft does not meet the requirements, there may be insufficient rigidity, reverse sealing leakage, and large opening torque. The butterfly plate structure is directly related to stiffness, so in addition to the flat shape, most of them are made into tank or truss shapes.
Self-lubricating bearings, most or all of the medium pressure on the butterfly plate is transmitted to the bearing through the shaft, so the bearing plays a very important role. Some foreign butterfly valves can be easily turned with one finger for small diameter valves, while some are heavy to turn, which is not only related to coaxiality, symmetry, processing accuracy, smoothness, and packing quality, but also to the lubrication of the shaft sleeve material, and the structural length of the butterfly valve is developing towards the short series, but this should be done with caution.