Flange connection is to fix two steel pipes, pipe fittings or equipment on a flange, and between the two flanges, with flange pads, bolted together to complete the connection. Some fittings and equipment have their own flanges and are also flanged. The welding quality of the flange and the pipe not only affects the eccentricity of the entire pipe, but also affects the strength and density of the pipe joint.
- The center of the flange should be in line with the center of the tube.
- The sealing surface of the flange flat welding flange shall be perpendicular to the center of the pipe. When the DN is less than 300 mm, the deflection is allowed to be 1 mm, and when the DN is > 300 mm, it is 2 mm.
- The flange connection should be the same size bolts, the installation direction is the same, that is, the nuts should be on the same side. The bolts and nuts that connect the valves should generally be placed on the side of the valve. When tightening the bolts, it should be symmetrical and evenly elastic. The tightened bolts shall not exceed 5mm or 2~3 buckles outside the exposed nut.
- The flange connection should be kept coaxial. The center deviation of the bolt hole should not exceed 5% of the hole diameter, and the bolt should be allowed to penetrate freely. The position of the screw holes of the flanges at both ends of the same pipe shall be consistent. The position of the screw holes on the flange of the pipe shall be consistent with the position of the flange hole of the flange on the matching equipment or pipe fittings.
- Bolt hole position on the flange: The bolt hole on the vertical pipe, the two bolt holes closest to the wall should be parallel to the wall surface; the bolt holes of the horizontal pipe, the uppermost two bolt holes should be kept horizontal. At the same time, the two connecting flanges should be parallel and natural, and the parallelism deviation should be no more than 2mm.
- The main features of the flange connection are easy disassembly, high strength and good sealing performance. When installing the flange, the two flanges must be kept parallel, the sealing surface of the flange should not be damaged, and it should be cleaned. The gasket used for the flange shall be selected according to the design regulations. Flange threaded connection (wire connection) flange and welded flange. Low-pressure small-diameter wire-bonded flanges, high-pressure and low-pressure large diameters are all welded flanges. The thickness of the flanges of different pressures and the diameter and number of connecting bolts are different.
Source: China Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)