Butterfly valve characteristics and installation and maintenance

Butterfly valve is also called flap valve, is a simple structure of the regulating valve, but also can be used for low pressure pipeline media switch control.

The butterfly valve is a kind of valve whose closing part is a disc and rotates around the valve shaft to achieve opening and closing. It is mainly used for cutting off and throttling on the pipeline. The opening and closing part of the butterfly valve is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjusting. The butterfly valve is usually less than 90°, the butterfly valve and the butterfly rod itself have no self-locking ability, in order to position the butterfly plate, the worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate self-locking ability, so that the butterfly plate stops in any position, but also improve the operating performance of the valve.

According to the sealing form, butterfly valves can be divided into two types: more sealed type and hard sealed type. The soft seal type is generally sealed by rubber ring, and the hard seal type is usually sealed by metal ring.

The butterfly valve can be divided into flange connection and sandwich connection according to the connection form.

According to the transmission mode, butterfly valves can be divided into manual, gear drive, pneumatic, hydraulic and electric several.

The butterfly valve can be divided into concentric butterfly valve, single eccentric butterfly valve, double eccentric butterfly valve and three eccentric butterfly valve according to the structure.

A. concentric butterfly valve: the structure of the butterfly valve is characterized by the stem axis, the center of the butterfly plate, and the center of the body in the same position. Simple structure and convenient manufacture. Common rubber lined butterfly valves belong to this category. The disadvantage is that the butterfly plate and the valve seat are always in the state of squeezing and scraping, which has large resistance and fast wear.

B.single eccentric butterfly valve: In order to solve the problem of squeezing the butterfly plate and the seat of the concentric butterfly valve, the single eccentric butterfly valve is generated, and its structural characteristics are that the stem axis deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate are no longer the rotating axis, dispersed and reduced the excessive squeezing of the upper and lower ends of the butterfly plate and the seat.

C.double eccentric butterfly valve: on the basis of the single eccentric butterfly valve is further improved molding is currently widely used double eccentric butterfly valve. Its structural characteristics are that the axis of the valve stem deviates from the center of the butterfly plate and from the center of the body. The effect of double eccentricity enables the disc to be quickly removed from the seat after the valve is opened, greatly eliminating the unnecessary excessive extrusion and scratching phenomenon between the disc and the seat, reducing the opening resistance, reducing wear, and improving the life of the seat.

D.three eccentric butterfly valve: to withstand high temperature must use a hard seal, but the leakage is large; For zero leakage, a soft seal must be used but not resistant to high temperatures. In order to overcome the contradiction of double eccentric butterfly valve, the butterfly valve is eccentric for a third time (deviating from the center line of the metal sealing surface).

Easy to open and close, labor-saving, fluid resistance is small, can be often operated.

Simple structure, small size, light weight.

Mud can be transported and less liquid can be deposited at the pipe mouth.

At low pressure, good sealing can be achieved.

Good adjustment performance.

Small operating pressure and temperature range.

Poor sealing.

1.before installation should check the butterfly valve specifications, pressure, temperature, corrosion resistance to meet the requirements of use. The parts should be checked for damage or loosening.

2.butterfly valve can be installed on any Angle of the pipeline, should be closed installation is appropriate; When welding the pipe flange, the valve sealing mouth should be blocked with a plate to prevent particles and debris from bruising the sealing surface. After welding, remove the valve, clean the valve sealing surface and the inner cavity of the pipeline, and then install the fixed valve.

3.during installation, the valve disc should be stopped in the closed position.

4.before installation, the sealing surface (both ends of the sealing surface, the sealing surface of the butterfly plate, the sealing surface of the seat) should be thoroughly wiped clean, remove dust and dirt.

5.the butterfly valve should be air-tested before installation, the opening and closing should be flexible, and the opening and closing position is consistent with the pointer indicating position.

6.the opening position should be determined according to the rotation Angle of the butterfly plate.

7. The butterfly valve with bypass valve should be opened before opening.

8.should be installed according to the manufacturer's installation instructions, large weight butterfly valve, should be set a solid foundation.

9.The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc-shaped disc rotates around the axis, the rotation Angle is between 0°-90°, and the valve is fully open when gc90° is rotated.

10.if the butterfly valve is required to be used as a flow control, the main thing is to correctly select the size and type of valve. The structure principle of butterfly valve is especially suitable for the production of large diameter valves. Butterfly valve is not only widely used in petroleum, gas, chemical industry, water treatment and other general industry, but also used in the cooling water system of thermal power station.

11.the commonly used butterfly valve has two kinds of butterfly valve and flange butterfly valve. Clamping butterfly valve is connected between two pipe flanges with a double-headed bolt, flanged butterfly valve is a valve with a flange, and the two ends of the valve are connected to the pipe flange with bolts.

12.The butterfly valve plate is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc disc rotates around the axis, the rotation Angle is between 0°-90°, and the valve is fully open when it is rotated to 90°.