Technical Requirements for Flange Connections
Generally, pipe flanges are only used for connecting flanged valves, instruments and equipment. Except the equipment that needs to be disassembled during maintenance, others had better not be connected with flanges. Excessive use of flanges will increase the possibility of leakage and reduce the elasticity of pipes. The flange end should be perpendicular to the center line of the pipe, and its verticality can be checked by the flange curve ruler or bare L-square. Flanges shall be connected in parallel, and the deviation shall be not more than 1.5‰ of the outer diameter of flanges and no greater than 2mm. Do not use the method of tightening bolts to eliminate the deviation.
Flanges should be kept in the same axis during connection, and the deviation of bolt holes should usually not exceed 5% of the diameter of the bolt holes. And ensure that bolts can easily pass through the bolt holes. The sealing surface of the flange must be machined smoothly, and there can be no defects such as grooves and sand holes in the radiation direction. Flange gaskets shall conform to the standards, and the square taper washer or double-layer gaskets are not allowed. When the soft gasket is used, the size of the gasket should be consistent with that of the flange sealing surface. The inner diameter of the gasket shall not be less than that of the pipe, and the outer diameter of the gasket should generally not be greater than bolt circle diameter.
Bolts for the flange connection shall be chosen according to specified materials and specifications. Installation direction shall be the same. The bolt shall be fastened symmetrically, and the length of the exposed bolt shall be not more than twice the pitch. Generally, the diameter of the bolt is 2-3 mm smaller than that of the bolt hole. After the bolts are fastened, they should be close to the flange, and no wedging method is allowed. There should be not more than one gasket when it is needed.
Flanges should be kept in the same axis during connection, and the deviation of bolt holes should usually not exceed 5% of the diameter of the bolt holes. And ensure that bolts can easily pass through the bolt holes. The sealing surface of the flange must be machined smoothly, and there can be no defects such as grooves and sand holes in the radiation direction. Flange gaskets shall conform to the standards, and the square taper washer or double-layer gaskets are not allowed. When the soft gasket is used, the size of the gasket should be consistent with that of the flange sealing surface. The inner diameter of the gasket shall not be less than that of the pipe, and the outer diameter of the gasket should generally not be greater than bolt circle diameter.
Bolts for the flange connection shall be chosen according to specified materials and specifications. Installation direction shall be the same. The bolt shall be fastened symmetrically, and the length of the exposed bolt shall be not more than twice the pitch. Generally, the diameter of the bolt is 2-3 mm smaller than that of the bolt hole. After the bolts are fastened, they should be close to the flange, and no wedging method is allowed. There should be not more than one gasket when it is needed.
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