At present, my country has established relevant standards for pipe flanges and equipment flanges. The pipe flange standards are HG20592 and HG20615, and the equipment flange standard is JB/T4700-4707. The standard requires designers to follow the standard specifications for design.

In practical applications, we found that if the flange selection is blindly selected according to the design standards, the cost is often higher, and the final effect is often not satisfactory. In the case of the same pressure rating and nominal diameter, comparing the pipe flange and equipment flange standards established in my country, we can see:

(1) The diameter of the bolt hole center circle of the equipment flange is much smaller than that of the pipe flange.

(2) According to the analysis and calculation of the force, it can be seen that the torque of the equipment flange is smaller than that of the pipe flange, so the equipment flange is thinner than the pipe flange.

(3) The outer circle of the pipe flange is larger.

Based on the above, we suggest that designers prefer to use equipment flanges to make pressure vessels. If beginners are not sure, it is best to choose flanges according to the standard. For the hand hole design, appropriate adjustments need to be made according to the actual budget. In the case of sufficient budget, standard pipe flanges are preferred. If the budget is insufficient, the equipment flange can be used for the design of non-standard hand holes.