Large flange refers to the flange that exceeds the size specified by relevant national departments. Generally, it refers to flange plate with size above DN2000. Such products are all welded products without screw thread. The specifications of screw thread products are usually DN15-DN100. The maximum size of the pressure standard from 0.25MPa to 1.6Mpa in the national flange standard GB/T9119-2010 is DN2000. The maximum pressure of 2.5MPa is DN800. The construction company shall provide drawings for the production of such flanges. There are three production processes: forging, rolling and splicing. If the product size is too large, it can only be rolled and spliced.

Materials include stainless steel 304, 316, 316L, 2205, 2507, 201, 304L, 321, carbon steel A3, Q235, A105, 10 #, 20 #, Q345, A182, 16MN, alloy steel 12cr1mov, 15crmov910, 15Mo3 15CrMoV, 12CrMoV, 45Cr, 50Cr, etc.

Theoretical calculation formula for large flange (carbon steel):

1. Divide (outer diameter inner diameter) by 2 to get the result.

2. Re use (outer diameter - above result) X above result X 0.0246615X thickness

After the above two steps, the theoretical weight of the large flange is obtained.

For example: 2600mm outer diameter, 2400mm inner diameter, 50mm thick large carbon steel flange

（ 2600-2400）/2=100mm

(2600-100)x100x0.0246615x0.05=308.2688KG

The weight is usually rounded off to two decimal places.

(Note: If it is a large stainless steel flange, just replace the X0.0246615 on it with 0.02491)