In terms of exemption from calculation for flat cover opening, the regulations in national standards, American standards, and European standards are different. I took the time to summarize:
1. National standard: 6.1.3 of GB/T 150.3 stipulates that it can only be applied to shells (cylinders, convex heads, and conical shells) without additional reinforcement. 6.3.4 There is no provision for non-reinforcing in the reinforcement of flat cover openings. Therefore, according to the GB/T 150 design of the equipment, the flat cover opening cannot be exempted from the calculation of opening reinforcement, regardless of the opening size.
2. US standard: ASME VIII-1 UG-36 (C) (3) stipulates the conditions for the exemption of opening reinforcement. UG-39 (a) stipulates that a single opening, its size does not exceed the limit of UG-36 (c) (3) and is less than or equal to 1/4 of the diameter or short diameter of the flat cover head, can be exempted from the reinforcement calculation. The thickness of the flat cover is not less than or equal to 10 mm, so the opening can only be 60 mm. Then, the standard flange cover hole meets the above requirements; whether the standard flange cover be directly selected? Think can and think not to have their reasons, not to discuss (because I think it is boring). Personal views can be! Note that the diameter of the flange cover is not the inner diameter of the cylinder or nozzle, as shown in the UG-34 diagram.
Note: the 89mm and 60mm here; there are a lot of AI-only standard pipes; LWN flanges or forged pipes for DN50 and DN80 need to be recognized.
Figure.UG-34 Some Acceptable Types of Unstayed Flat Heads and Covers
3. European standard: Section 184.108.40.206 of EN 13445-3 stipulates the exemption of opening reinforcement of shell. 1.6.2 section of the flat cover opening reinforcement section does not provide for the calculation of the opening reinforcement, but 10.6.1.2 standard pipe flange cover opening reinforcement calculation conditions: the opening does not exceed the standard pipe flange hole. The thickness of the flat cover is greater than or equal to 50 % of the diameter of the bolt hole.
In the analysis of the mixing port on the flange cover just two days ago, several flanges covers and flange cover openings (no takeover) were made by the way; the dimensions of the three models are the same (except for openings), the bolt loads are the same, the pressures are the same, and the constraints are the same. The stress cloud diagram is shown below; pay attention to the maximum stress and the approximate stress value of the opening edge. The openings on the flange cover are usually connected by a nozzle, except for the connecting stirring port. The following analysis of the results of the provisions of the European standard EN 13445 is reliable.
Flange cover does not open the hole.
The center of the flange cover has a hole with a diameter of 370mm.
The center of the flange cover has 150 holes in diameter.