(1) flange connection should adhere to the same axis, and the center deviation of its bolt hole generally does not exceed 5% of the hole diameter. The connecting bolts of the flange should be the same specification, the equipment direction should be common, and the bolts should be symmetrical and uniform when tightening bolts.
(2) the unequal oblique washer shall not be used to compensate for the uneven degree of the flange. No double layer washer should be used. When the large diameter washer needs splicing, no flat port should be used, and oblique lap or labyrinth should be adopted.
(3) for the convenience of loading and unloading flanges and fastening bolts, the distance between flange plane and support and wall should not be less than 200mm.
(4) when tightening bolts, they should be carried out in symmetrical sequence to ensure uniform force of gaskets.
(5) in case of any of the following situations, bolts and nuts should be coated with molybdenum disulfide, graphite oil or graphite powder for future disassembly.
1) stainless steel, alloy steel bolts and nuts; 2) pipeline planning temperature above 100 C or below 0 C; 3) outdoor equipment; 4) atmospheric corrosion or corrosive medium.
(6) use metal gaskets such as copper, aluminum and mild steel before annealing.
(7) flange joint bolts for high temperature or low temperature pipes should be tightened or tightened according to the following rules during trial operation.