Principles of flange design:

1.When designing gaskets, the gasket load should be controlled as small as possible.

2.When designing bolts, the center circle diameter of the bolt should be controlled as small as possible to obtain the smallest flange torque, following the principle of "minimum load".

3.The proportion of the flange neck and flange ring structure is appropriate, allowing each part of the flange to fully exert its strength and ensure sufficient stiffness, following the principle of "full stress".

Notes:

1.The flange used for the connection between the inner diameter and the nominal diameter of the vessel or the connection between the shell and the cap should be selected according to the current industry standard NB/T 47020-47027-2012 for pressure vessel flanges, gaskets, and fasteners. When using steel pipes to make the body of the vessel, the connection between the bodies or the connection flange between the cylinder and the cap should be selected according to the PN series standard in the current industry standard HG/T20592 for steel pipe flanges.

2.The flange used for the connection between vessel shells (including copper pipes as simplified body) or the connection between the shell and the cap in English units should be selected according to the current industry standard "Steel Pipe flanges~HG/T 20615 Class series" and the current industry standard "Large diameter steel pipe flanges" HG/T 20623 Class series standards.

3.For vessels containing explosive and moderately toxic hazardous media, the nominal pressure level of the container flange should not be less than 0.6MPa; For vessels containing extremely and highly toxic and highly permeable media, the nominal pressure rating of the vessel flange should not be lower than 1 0MPa.

4.For the calculation of girth flanges used for clamping tube plates in U-shaped and floating head heat exchangers, the design pressure should be taken as the higher design pressure of the two stages, and the calculated temperature should be taken as the respective design temperature. The design pressure and temperature of bolts and gaskets should be determined based on the higher parameters of the two stages.

5.When designing flanges according to national standards, corrosion allowance needs to be deducted from the inner diameter and thickness of the large and small ends of the flange. For neck welded flanges, when the thickness of the small end of the flange is greater than the thickness of the cylinder, the thickness of the cylinder should be taken as the thickness of the small end during calculation.

6.When the girth flange of the heat exchanger is equipped with a pass partition, the influence of the pass partition should be considered.

7.The flange of tower equipment needs to consider the influence of bending moment and calculate the equivalent calculation pressure.

8.The thickness of the flange ring does not need to consider the corrosion allowance of the medium. When there are no appropriate anti-corrosion measures, the atmospheric environment can be considered.

9.External pressure flanges with low design pressure can be directly calculated based on internal pressure design, and their bolt area only needs to be considered according to the pre tightening state. If the flange is subjected to internal pressure and external pressure respectively during operation, the flange should be designed separately according to the two pressures and meet the requirements simultaneously.

10.For occasions with high temperature, high pressure, no leakage allowed, and few disassembly times, the flange connection type should use welded ring gaskets to seal the flange.

11.For containers containing extremely and highly toxic hazardous media, medium toxic hazardous media with strong permeability, liquefied petroleum gas, and equipment flanges under low temperature, high temperature, and fatigue conditions, neck butt welding should be used.