After taking over the modified coil, should the inner diameter or the outer diameter be maintained?
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Example: When a pipe of φ600×16mm is converted to a coil, it is replaced with a 18mm thick plate. I would like to ask whether it is necessary to ensure an inner diameter of φ568 or an outer diameter of φ600 at this point? If the inner diameter is guaranteed, the opening will become larger – will this affect the strength? If the outer diameter is guaranteed, the inner diameter will decrease, and if there are internal components inside the equipment, they may not fit. Seek answers to my doubts!
The thickness difference is 2 millimeters; the above two factors are not considered critical. Generally, consideration is given to the matching of pipes and flanges.
Ignoring that example for now, I would like to ask about using sheet metal in place of pipes: when the thicknesses are different, what considerations should be taken into account to ensure consistency in either the inner diameter or the outer diameter?
1. If the external interface involves pipe butt jointing, the dimensions of the pipes must be taken into account; the groove on the inside should be determined based on the pipes being joined. If the wall thickness is too large, edge trimming also needs to be considered. 2. If it is a flange, consider the connection dimensions between the pipe and the flange; determine whether it is necessary to modify the flange diameter (including the pipe insertion dimension).
1. Opening reinforcement: If the welded joints of the pipe (Type B) meet the requirements with 100% Grade II RT or Grade I UT testing, no further action is necessary. In fact, the length generally does not exceed 250 mm, and both partial and full inspections are carried out on a single piece. 2. If local detection is used, although the thickness increases, the weld joint coefficient is 0.85, so re-calculation for reinforcement is required; in most cases the calculation will pass.
According to you, it should be understood as a device with special functions; in that case, the requirements regarding the inner diameter need to be taken into account. If it’s just a pipe, then consider meeting the outer diameter requirement.
Pipe flanges are designed based on outer diameter and wall thickness; if the wall thickness of the rolled pipe differs significantly from the original design, the inner diameter of the pipe flange should be adjusted accordingly.
In addition to considering the issue of matching the takeover to the flange connection, the issue of flow velocity inside the pipe also needs to be taken into account. For the mechanical engineering field, ensuring the strength of pipes, whether it is the inner diameter or the outer diameter, is not a problem.
Since plate coils are used in place of pipes, even if the thickness is increased, the outer diameter can be maintained without affecting the manufacturing process
Personally, I suggest that the designer confirm it and sign off. Changing the thickness affects not only the changes in the joint structure, but also flow velocity, pressure difference, resistance, plastic deformation, load, reinforcement through openings, groove shape, and in special cases, heat treatment methods as well. The material can be used in greater thicknesses instead of thinner ones, which requires coordination by the designer. Strength is just one of the most intuitive influencing factors, and it is also the easiest to pay attention to. In fact, other factors are also decisive in determining the performance and safety of equipment.