1. First of all, the size of the outer diameter of the flange D1.D2 is accurately measured. If the measured data is 157.5mm, the size is 157.5mm.

2. Measure the size of large flange clearance B, and measure four points on the circumference (uniform cloth).

3. Measure the enlarged part of the depth C(the size between the outside of the flange and the bolt), and measure the size of C at the position 1234 of the flange respectively, and select the smallest size.

4. Measure the size of two large flanges with different centers (fault port) and select the size of the largest fault port of two flanges.

5. Finally, the measured data should be filled in the table.