Butterfly Valve Basics: Working Principles, Features and Applications

Butterfly valve, also known as flap valve, is a kind of regulating valve with simple structure. Butterfly valve can be used for switch control of low-pressure pipeline medium. It means that the closing member (disc or butterfly plate) is a disc, which rotates around the valve shaft to achieve opening and closing of a valve. Today, we are going to introduce what is a butterfly valve to you. We hope that you can have a general idea about it after reading.

Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. It mainly plays the role of cutting and throttling on the pipeline. The butterfly valve opening and closing part is a disc-shaped butterfly plate, which rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment.

Working principle

Butterfly valve is a kind of valve that uses a disc opening and closing member to reciprocate about 90° to open, close or adjust the flow of the medium. Butterfly valve not only has simple structure, small size, light weight, low material consumption, small installation size, small driving torque, simple and fast operation, but also has good flow regulation function and closing sealing characteristics at the same time. Butterfly valves are widely used. The variety and quantity of its use continue to expand. Its reliability and other performance indicators have reached a high level.

With the application of chemically resistant synthetic rubber on the butterfly valve, the performance of the butterfly valve has been improved. Synthetic rubber has the characteristics of corrosion resistance, erosion resistance, dimensional stability, good resilience, easy forming, and low cost. Therefore, butterfly valve can choose synthetic rubber with different properties according to different use requirements to meet different working conditions.

Structure

It is mainly composed of valve body, valve stem, butterfly plate and sealing ring. The valve body is cylindrical, with a short axial length and a built-in butterfly plate.

Features

The butterfly valve can be used to cut off, connect and adjust the medium in the pipeline. It has the characteristics of good fluid control and closing sealing.
Butterfly valve can transport mud, with the least amount of liquid accumulated at the pipe mouth. At low pressure, a good seal can be achieved. It has good adjustment performance.
The streamlined design of the butterfly plate makes the loss of fluid resistance small. In this end, it can be described as an energy-saving product.
The valve stem is a through-rod structure, which has been quenched and tempered, and 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 move up and down. The packing of the valve stem is not easy to be damaged, and the sealing is reliable. The butterfly valve is fixed by the taper pin of the butterfly plate, and the overhanging end is designed to prevent the valve stem from breaking out when the connection between the valve stem and the butterfly plate is accidentally broken.
The connection methods include clip connection, butt welding connection and lug-to-clip connection.
The drive forms include manual, worm gear drive, electric, pneumatic, hydraulic, electro-hydraulic linkage and other actuators, which can realize remote control and automatic operation.

Advantages

The opening and closing is convenient and quick, labor-saving, and the fluid resistance is small, which can be operated frequently.
Simple structure, small size, short structure length, small volume and light weight, suitable for large-diameter valves.
The mud can be transported, and the liquid accumulation at the pipe mouth is the least.
Under low pressure, good sealing can be achieved.
Good adjustment performance.
When fully open, the effective flow area of the valve seat channel is larger and the fluid resistance is smaller.
The opening and closing torque is small. As the discs on both sides of the rotating shaft are basically equally affected by the medium, and the direction of the torque is opposite, the opening and closing is more labor-saving.
The sealing surface material is generally made of rubber and plastic, so the low pressure sealing performance is good.
Easy to install.
The operation is flexible and labor-saving, and manual, electric, pneumatic and hydraulic methods can be selected.

Disadvantages

The operating pressure and working temperature range are small.
Poor sealing.

Classification

Butterfly valve can be divided into offset plate type, vertical plate type, inclined plate type and lever type according to the structure.

According to the sealing form, there are two types of soft sealing type and hard sealing type. The soft seal type is generally sealed with a rubber ring, and the hard seal type is usually sealed with a metal ring.

According to the connection type, it can be divided into flange connection and wafer connection.

According to the transmission mode, it can be divided into manual, gear transmission, pneumatic, hydraulic and electric

Applications

The butterfly valve is usually less than 90° from fully open to fully close. Butterfly valve and butterfly stem have no self-locking ability. In order to locate the butterfly plate, a worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate have self-locking ability, so that the butterfly plate can stop at any position, but also improve the operation performance of the valve. The characteristics of industrial-specific butterfly valves are high temperature resistance. The applicable pressure range is also high. The valve has a large nominal diameter. The valve body is made of carbon steel and the sealing ring of the valve plate uses a metal ring instead of a rubber ring. Large high temperature butterfly valve is made of steel plate welding, mainly used for flue air duct and gas pipeline of high temperature medium.