The surface of the flange on the pipe shall be perpendicular to the center line of the pipe, and the position error between the flange bolt and the center of the pipe shall be within the allowable range. Center line of valve and pipe should be the same before installation.

The flanges of valves and pipes shall be free of damage, scratches, etc., and kept clean, especially when using metal gaskets. The flanges shall be in the same groove as the gaskets to ensure a good seal.

Flange fastening should be avoid uneven force, in accordance with the symmetrical direction, cross direction, uniform and orderly fastening.

When tightening bolts, the tool must matches the nuts. During using hydraulic and pneumatic tools to tighten the star wheel, do not exceed the specified operating distance.

When connecting two flanges, the flange sealing face and gasket should be uniformly pressed to ensure that the flanges are connected under the same bolt stress.

After flange all installed, ensure that all bolts and nuts are tightened evenly.
Fastening bolts and nuts in order to prevent vibration caused by loosening.Washers should be used. In order to avoid adhesion of thread joints under high temperature, anti-adhesive should be applied to the installation thread parts.

For high temperature valves above 300 degrees, flange joint bolts, bonnet fastening bolts, pressure seals and packing seal bolts must be tightened again after temperature increases.

Low temperature valve usually installed at room temperature. Flange, washer, bolts and nuts shrink as a result because temperature difference. Due to the different materials of these parts, their linear expansion coefficient is also different, thus forming the environmental conditions that are very easy to leak. From this objective situation, it is necessary to adopt the following methods when tightening bolts at room temperature. Consider the torque of shrinkage coefficient of each component at low temperature.