Follow the procedure and method of connecting flange according to national standard
Pipe end and flange connection
A. The end of the pipe is generally cut by saw or oxyacetylene flame. The incisions of the tubes are examined with a curved ruler. The end face of the pipe shall be perpendicular to the pipe axis, and the deviation shall not be greater than 1.5mm.
B. The flange can be assembled after the pipe end is machined and checked. A special flange bending ruler can be used to check the perpendicularity of the flange end face and pipe axis when pairing. One end of the flange ruler should be close to the pipe skin and the other end should be close to the flange face. Then the flange and pipe end should be spot welded at three points on the circumference. The gap between the flange ruler and the flange end face is measured by the feeler ruler in two directions of 90℃. The deviation shall not exceed 0.15% of the flange diameter and shall not be greater than 2mm. At the same time, check the distance between the inside of the pipe opening and the flange sealing surface, which should be no less than 1.3-1.5 times of the pipe wall thickness. If the deviation is found to exceed the allowable value, the deflection shall be eliminated before spot welding. If all deviations are checked in accordance with the requirements, the welding of pipe and flange can be carried out, and the welding process must meet the technical requirements.
Flange to flange connection
A. Operating steps (take welding flange as an example). Check whether the flange is in accordance with the design requirements → pipe end prefabrication → pipe end and flange assembly welding → gasket inspection → gasket sealing coating → flange fastener selection, inspection, thread paint treatment before installation → flange installation group alignment, pad initial tightening → pipeline straightness, wrong address, flange parallelism inspection → final tightening.
B. Operation method. When connecting the flange, make a preliminary leveling and alignment, add the initial tightening of the cushion, and then check the flatness again. The center of the gasket must be kept in line with the axis of the pipe. After confirmation, use the wrench of the corresponding size of the bolt and tighten it one by one in 2-3 times in a symmetrical order.
