I. Preparations before large flange measurement:
1. Before measuring, according to the position of the large flange, firstly draw a sketch of each large flange connected to the equipment and serially number them so that the fixtures are installed in the same number and installed in a certain way and principle to ensure normal use.
2. During installation, large flanges may have different outer diameters, misalignment (concentricity), and unequal pad thickness. Therefore, the processed fixtures should not be interchangeable with the flanges on the side, so measure the dimensions of each part. And numbering is the key to fixture processing and installation.

3. When measuring, it is best to arrange three people, two of them are measuring, one is proofreading and filling in the form, and the measuring tools are vernier calipers. If there is no condition, external calipers and steel rulers can be used. Measurement is a meticulous work, and it is the premise of fixture installation. Measurement and recording must be prepared correctly, and the form must be filled carefully and clearly. It is necessary to cooperate with each other in the actual measurement work, and to cooperate and use according to the correct principle.
4. The measured flange data is filled in the table.

In large flange measurement:
1. First measure the dimensions of the flange outer diameter D1.D2 accurately. If the measured data is 157.5mm, this dimension is 157.5mm.
2. Measure the size b of the large flange gap, and measure four points (evenly distributed) on the circumference.
3. Measure the enlarged part of the depth C (the dimension between the flange's outer edge and the bolt), and measure the size of C at the flange's 1234 position, and choose the smallest size. 4. Measure the size of the concentric (offset) of the two large flanges, and choose the size of the largest offset of the two flanges.
5.Fill in the actual measurement data in the table.