Installation of butterfly valve

Below are recommendations for the installation of butterfly valves in a flange design with a soft polymer seal (gasket):

The seal between the body of the butterfly valve and the corresponding flanges is provided by an elastic gasket made of a polymer material. It is not necessary to install additional gaskets.
The butterfly valve should freely fit between the corresponding flanges, in order to avoid bending and deformation of the elastic insert (gasket).
For valve installation, it is recommended to use collar flanges (welded together). In the case of installation between flat flanges (slipped onto a pipe), the edge of the pipe should not protrude beyond the plane of the flange that contacts the valve body.
The inner diameter of the flange should correspond to the inner diameter of the valve, otherwise the disk may be blocked and unable to be opened.
The surfaces of the flanges that come into contact with the valve should be parallel.
The bolts should be tightened when the butterfly valve is open by one quarter. Otherwise, the disk may be blocked by the compressed polymer insert, and opening it will result in deformation of the insert and a breach of the seal. The nuts should be tightened gradually, in a criss-cross pattern.
It is not permissible to use flanges of anti-vibration inserts as flanges. The polymer material of such inserts should not protrude beyond the surface of the flange and, like in a disc valve, act as a flange seal.
The valve body should not be subjected to rotational, bending, or compressive forces from the connected pipeline.
The butterfly valve should be installed after welding work. In order to avoid damage to the sealing insert, welding work should not be carried out near the valve.
On horizontal pipelines, butterfly valves are recommended to be installed with the axis of the stem in a horizontal position, since sediment may accumulate in the lower part of the pipeline, which can lead to the valve getting stuck.
The bolts should be tightened gradually, in a criss-cross pattern, with a torque wrench. After tightening, it is recommended to check the tightness of the valve with a pressure gauge.