There are two kinds of flanges in petroleum and chemical industry, one is the pressure vessel flange standard, and one is the pipe flange standard.
Both flat and butt welding flange have two kinds of ring with ring and no ring. When the equipment is made of stainless steel, carbon steel flange 7 and stainless steel liner can be used to save stainless steel.
When using flange standard to determine flange dimensions, it is necessary to know the nominal diameter of flange and nominal pressure. The nominal diameter of pressure vessel flange is the same as the nominal diameter of the pressure vessel. For example, pressure vessels of DN 1000mm should be used with pressure vessel flange of DN 1000mm.
Flange nominal pressure is determined to be related to flange's operating pressure, operating temperature and flange material. Because in the flange size series, when calculating the thickness of the flange, with 16 MNR at 200 ℃ of machinery for the benchmark. So regulation to benchmark the identified flange dimensions, at 200 ℃, it allows the operating pressure is considered a nominal pressure with the size of the flange. For example, the so-called nominal pressure PNO. 6 MPa flange, is refers to have such a specific size of the flange, the flange is made of 16 MNR, at 200 ℃, it allows the operating pressure is 0.6 MPa. If the PN0.6 MPa flange is used under the condition of higher than 200 ℃, then its operating pressure will be lower than the nominal pressure of 0.6 MPa. Conversely, if use it for below 200 ℃ condition, as defined by the 200 ℃ is the work pressure.
If change the material of flange to Q235 - A, then A Q235 A steel mechanical properties than 16 MNR is poor, the nominal pressure PN0.6 MPa flange, even in the operation of 200 ℃, it allows the operating pressure will be lower than the nominal pressure. On the other hand, if the material of flange from 16 MNR to 15 MNVR, then, due to the mechanical performance is better than that of 16 MNR 15 MNVR, the nominal pressure PN0.6 MPa flange, at 200 ℃, it allows the operating pressure will be greater than its nominal pressure.
As long as the nominal diameter of the flange, the nominal pressure is determined, the flange size is also determined. As for the operating pressure of this flange, it depends on the operating temperature of the flange and the material used.