When flanges and gaskets and boring bolts together form a sealed joint body, the effect of pressure sealing can be achieved. Therefore, when choosing a flange, consider the choice of gaskets for flanges, the choice of flanges for studs, and the matching of flanges, gaskets, studs, and nut materials.
Selection principle and flange type Corrosion allowance; Flange gasket selection; Flange selection with column; Flange, gasket, stud, nut material matching; .
1. Corrosion allowance for selection principle and flange type
1 Selection principle
All pressure vessel flanges should preferably adopt the standard flanges (including gaskets) specified in JB/T 4700?4707-2000. Pressure vessel flanges that are selected according to the standard flanges can be exempt from the calculation of GB150 "Steel Pressure Vessels".
2 corrosion margin
The corrosion margin of type B flat welded flange is not more than 2mm. When the corrosion margin exceeds 2mm but not more than 3mm, the thickness of short section should be 2mm. The applicable corrosion margin of long neck butt welding flange is not more than 3mm.
2, the choice of flange gasket
The gaskets for pressure vessel flanges are non-metallic soft gaskets, spiral wound gaskets, and metal-encased gaskets, which are specifically designed according to JB/T 4704—2000 “Non-Metallic Soft Gaskets” and JB/T 4705—2000. "Gasket" and JB/T 4706-2000 "Metal Packing Gasket" provisions.
3, the choice of flange studs
1 Selection of stud material
The stud material for the pressure vessel flange is selected from the table.
2 stud type and size
The type and size of equal-length double-headed studs for flanges are to comply with JB/T 4707-2000 "Double-head studs of equal length".
4, flange, gasket, stud, nut material matching
Matching of A-type flat welding flange, B-type horizontal welding flange and long neck butt welding flange (hereinafter abbreviated as A, B, and long neck flanges), gaskets, studs, and nut materials (including applicable temperature range ) See the table.
The hardness of the stud (Brinell hardness, HB) should be 20-30 higher than the hardness of the nut, and the material of the same strength level can be achieved by different heat treatment conditions.