1. The connection of the connecting flange should maintain the same axis, the center deviation of the bolt hole should not exceed 5% of the diameter of the hole, and the bolt should be free to penetrate. The connecting bolts of the flange should be of the same specification, the installation direction should be the same, and the bolts should be tightened symmetrically and evenly.
2. It is not allowed to use inclined washers with different thicknesses to make up for the non-parallelism of the adapter flange. Double gaskets must not be used. When large-diameter gaskets need to be spliced, they should not be butted with flat butt joints or labyrinths.
3. In order to facilitate the installation and disassembly of the connecting flange, tighten the bolts, and the distance between the plane of the connecting flange and the bracket and the wall should not be less than 200mm.
4. When tightening the bolts, it should be carried out in a symmetrical and crossed sequence to ensure that the gasket is evenly stressed.
5. In the following cases, the bolts and nuts should be coated with molybdenum disulfide, graphite oil or graphite powder to facilitate disassembly in the future: 1) Stainless steel, alloy steel bolts and nuts; 2) The design temperature of the pipeline is higher than 100 ℃ or lower than 0 ℃; 3) outdoor installation; 4) atmospheric corrosion or corrosive medium.
6. Use copper, aluminum, mild steel and other metal gaskets, and annealing treatment should be performed before installing the adapter flange.
7. The flange connection bolts of high temperature or low temperature pipelines should generally be hot-tightened or cold-tightened according to the following regulations during trial operation: 1) Hot-tightening or cold-tightening should be carried out after maintaining the working temperature for 24 hours; 2) Tightening When tightening the pipe bolts, the relatively large internal pressure in the pipeline should be determined according to the design pressure. When the design pressure is less than 6MPa, the maximum internal pressure for thermal tightening is 0.3MPa; when the design pressure is greater than 6MPa, the maximum internal pressure for thermal tightening is 0.5 MPa. Cold tightening should generally be carried out with pressure relief. Hot and cold tight tightening should be moderate and safety measures should be taken.
8. It is not allowed to directly bury the flange connection. There should be inspection wells at the flange connections of buried pipelines. If they must be buried, anti-corrosion measures should be taken.