The Advantages and Disadvantages of Butterfly Valve and Its Installation and Maintenance

Figure 1: The appearance and design mode of a kind of common butterfly valve.

Butterfly valve is a kind of valve whose closing part (valve clack or butterfly plate) is a disc and rotates around the valve shaft to open and close. It is mainly used for cutting off and throttling on the pipeline. Opening and closing part of butterfly valve, being a disc-shaped plate, rotates around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjustment.

The butterfly valve is usually rotated less than 90 degrees from full opening to full closing. The butterfly valve and the butterfly rod have no self-locking ability. In order to position the butterfly plate, a turbine reducer should be installed on the valve rod. The adoption of turbine reducer can not only make the butterfly plate equip self-locking ability, stop the butterfly plate at any position, but also improve the operation performance of the valve.

The industrial butterfly valve is characterized by high temperature resistance, widely applicable pressure range, large nominal diameter of the valve, carbon steel valve body, and metal ring instead of rubber ring for the sealing ring of the valve plate. Large high-temperature butterfly valve is made of welded steel plate, which is mainly used for high-temperature air and flue gas duct and gas pipeline.

Advantages of Butterfly Valve

Convenient and rapid opening and closure, labor-saving, small fluid resistance, and frequent operation.
Simple structure, small size, and light weight.
Transporting muds, and the least amount of accumulated liquid at the pipe line.
Great sealing under low pressure.
Excellent adjustment performance.

Figure 2: The diagram of stainless butterfly valve.

Disadvantages of Butterfly Valve

The flow adjustment range is not large. When the opening degree approaches to30%, the flow will increase by more than 95%;
Due to the limitations of the structure and sealing materials of the butterfly valve, it is not suitable for high-temperature and high-pressure pipeline systems. The general working temperature is below 300 Celsius degrees and nominal pressure below 40;
The sealing performance is worse than that of ball valve and cut-off valve, so it is used in situations where the sealing requirements are not very high.

The Installation of Butterfly Valve

Butterfly valve according to the structure of can be divided into the plate, vertical plate, inclined plate and leveraged. According to the sealing form, it can be divided into two types: soft sealing type and hard sealing type. The soft sealing type generally adopts rubber ring sealing, and the hard sealing type usually adopts metal ring sealing. 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 electrical.

Figure 3: The front and back appearance and design mode of electrical butterfly valve.

Notices for installation should be paid following attention:
Valve clack should be stopped at the closing position in the installation process.
The opening position shall be determined in accordance with the rotation angle of the butterfly plate.

For butterfly valve with bypass valve, the bypass valve shall be opened before opening.
Installation should be in accordance with guidance instructions provided by manufacturer, and butterfly valve with heavy weight should be fixed on a solid foundation.

Maintenance of Butterfly Valve

Attention should be paid to check whether there is water in the pneumatic actuator during valve maintenance. In wet seasons, the accumulated water in the air storage tank of the air compressor causes the transmission mechanism or transmission shaft sleeve to rust.

In frozen winter, the accumulated water in the air storage tank of the air compressor is frozen after entering the pneumatic actuator, resulting in large torque during the operation of pneumatic actuator, damage to the transmission parts, and manual operation is also impossible. If forceful manual operation is made, the internal components of pneumatic actuator will be damaged.

Figure 4: Professional staff is repairing and maintaining the butterfly valve.

During maintenance, the drain valve in the air storage tank of air compressor shall be opened irregularly to drain the internal water. For butterfly valve with handwheel, the turbine case cover should be opened to check whether the lubricant is normal within about 6 months’ operation, and maintain an appropriate amount of lubricating oil.

Related Info