What is the difference between pipe flanges and equipment flanges, and can they be used interchangeably?

The applicable pressure range for equipment flanges is between 0.25–6.4 MPa, while the pressure rating for face pipe flanges can reach 25 MPa. The temperature range suitable for equipment flanges depends on their design and material, whereas the temperature range for pipe flanges depends only on the material. Their nominal diameters also differ: one uses the inner diameter as the nominal value, while the other uses the outer diameter. How can one replace one with the other? If replacement is necessary, it will result in a non-standard flange. Additionally, Class C welds at A and B type equipment flanges require MT or PT-100% inspection, whereas flat weld pipe flanges do not have such requirements. Sometimes, there are significant differences in the pressure and temperature ratings between flanges made from the same material. These are just some points that come to mind; you can check the standards for each type and compare them.

When the cylinder is made of seamless steel pipes, under conditions that meet the design requirements, pipe flanges can be used in place of equipment flanges.

If the housing is made of pipes, pipe flanges can be used; if the connecting tubes are welded from sheet metal, vessel flanges can be used. There is no essential difference in the stress conditions and sealing requirements between pipe flanges with large diameters and container flanges with small diameters. However, for the convenience of piping, pipe flanges should be used as much as possible; container flanges have a more compact structure, and under the same diameter, pressure, and temperature conditions, they weigh less.