The correct installation method of butterfly valve and often encountered problems

1. Analysis of elastic structure and problems

Elastic structure hard seal butterfly valve by the valve body, valve disc, stem, seat, pressure ring and other main parts.

The structure and function of the pressure ring: the side of the pressure ring is the sealing surface of the valve body and the sealing surface of the pipe flange becomes a sealing pair, the side has a bolt hole, the bolt is used to press the pressure ring to fix the seat, and the valve body is connected as one, constituting the total structural length of the valve.

Because of the screw aperture on the side of the pressure ring, the effective sealing surface diameter will be reduced. From the user's use of flange, most of the use of flat welding flange, its internal warp also known as 10~20mm. In this way, the effective sealing surface will be reduced. If the valve and the pipe flange have different hearts during the installation process, they will be misplaced on the bolt aperture. At this time, the inner hole of the pipe flange will expose the bolt aperture, resulting in leakage here. The leakage characteristic is that the medium flows out from the back of the pressure ring.

2. The direction of the arrow on the valve body refers to the direction of the pressure of the medium

Usually the arrow direction cast on the valve body refers to the flow direction of the medium, the user sees the arrow, logically according to the direction of the flow and arrow installation.

But in the eccentric structure of the butterfly valve, such installation sometimes there are some problems, say an example: Eccentric butterfly valve is installed in accordance with the flow direction and the flow of the medium, the medium in the tube is liquid, after the valve is closed, if the pressure of the original medium inlet direction, reduce or zero, the outlet of the medium backflow backflow, if it is a high supply, the medium at a high level and produce pressure, the pressure is greater than the inlet pressure, the valve will bear the effect of reverse pressure, Because the ordinary hard seal butterfly valve is a one-way valve, it is not conducive to the sealing of the butterfly valve, and there will be leakage.

From the above example, it is concluded that the arrow direction of the butterfly valve body refers to the pressure direction of the medium. The user should know the direction of the medium pressure after the valve is closed before installation. The direction of the arrow of the free valve body is consistent with the direction of the medium pressure. The correct use can be achieved, and the tightness is maintained in good condition.