1, valve and piping flange surface should be free of damage, scratches, etc., and keep clean. In particular, when the metal washer is used, the grooves of the flanges should be in agreement with the gaskets, and they should be coated with red lead to ensure the sealing condition is good.

2. The error between the flange surface of the piping and the center line of the piping and the bolt hole of the flange should be within the allowable value. Valve and piping center line should be consistent before installation.

3, when connecting two flanges, first make the flange sealing surface and the gasket evenly pressed, thus ensuring that the flange is connected by the same bolt stress.

4, when fastening bolts, use the wrench which is matched with the nut. When using oil pressure and pneumatic tools to fasten, pay attention not to exceed the specified torque.

5, flange fastening should avoid uneven force, and should be tightened according to the direction of symmetry and crossover.

6, after flange installation, make sure that all bolts and nuts are evenly fastened.

7, the material of bolts and nuts must be in accordance with the regulations. After fastening, the bolt head should be exposed two screws from the nut.

8, bolts and nuts fastening, in order to prevent vibration caused by loosening, we need to use washers. In order to avoid adhesion between threads at high temperature, the thread part should be coated with adhesive when installing.

9. For high temperature valves above 300 C, when the temperature rises, it is necessary to tighten the flange connection bolts, the fastening bolts of the valve cover, the pressure seal and the stuffing cover bolt again.

10, when the low temperature valve is in the condition of air temperature when the valve is installed, because of the temperature difference, the flange, gasket, bolt and nut are contracted, and because of the different material of these parts, the coefficient of expansion of each line is different, and the environment condition is very easy to leak. In view of this objective situation, when tightening bolts at atmospheric temperature, the torque must be taken into account when the components of the parts are at low temperature.