The followings are the methods which used to install flanged valves:
1. The surface of valve and piping flange should have damage, scratch and other defects. Besides, they should be kept clean. Especially when valve adopts metal gasket, grooving on flange disc should coincide with gasket. Flange disc should be coated with red lead for match lapping, to keep good sealing.
2. Error between surface of piping flange and perpendicularity of piping center line or bolt hole of flange should be located at the range of allowable value. Installation should be carried out after valve being in conformity with piping center line.
3. When connect two flanges, firstly, sealing face of flanges should be compressed equably with gasket, so that can ensure that flanges are connected depending on equivalent bolt stress.
4. When fasten bolt, used spanner should be matched with nuts. When use oil pressure or pneumatic tools for fastening, torque should be noticed that cannot exceed than specified toque.
5. Fastening flange should be in case of uneven pressure. Flange should be screwed tightly in accordance of the direction of symmetry and intersection.
6. After installing flanges, all of bolts and nut should be confirmed to be fastened tightly.
7. The materials used for bolts and nuts should conform to regulations. After being fastened, bolt heads using two screw pitches exposing from nuts is appropriate.
8. The fastening of bolts and nuts should avoid loosen which is caused by vibration and gasket should be used. To avoid adhesion between screw threads under high temperature, screw thread should be painted with anti-sticking agent during installation.
9. For high temperature valves which are used under the temperature higher than 300℃, after temperature rising, flange connection bolt, bonnet fastening bolt, pressure sealing bolt and packing gland bolt must be screwed tightly again.
10. Low temperature valve is under atmospheric temperature during installation. Due to temperature difference occurring, flange, gasket, bolt and nuts shrink. In addition, the raw materials of these parts are different from each other and their own coefficients of linear expansion. So, the environmental conditions which can easily leak are formed. In terms of such objective circumstances, when using fastening bolts under atmospheric temperature, torque that every part shrinks under low temperature must be taken into consideration.
