Must the lugs and shims not be located in the head transition zone?
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This post was last edited by zhangjuhua on 2018-12-5 at 18:14. When calculating the local stresses in attachments such as lifting lugs on the head, it often happens that \"the attachment is located in the transition zone of the head, and the program stops running\", thus preventing further calculations. According to standard 21574 for lugs, the distance from the center of each lug to the center line should be less than 0.7R; meeting this requirement is specified in the standards. Should we follow these guidelines and place the lugs at a distance of 0.6R or even less? When lifting, there is generally no internal pressure. The book mentions that the transition zone is problematic when under internal pressure, but isn’t it also allowed to use lug shims in the absence of internal pressure? In fact, holes can be made in the transition zone; it’s just that the wall thickness of the connecting pipe may need to be increased. Why then aren’t lug shims allowed in the transition zone?
It can be located in the transition zone; we have conducted stress analysis and found no significant impact, plus there is no internal pressure during lifting.
The lifting lugs themselves are subjected to stress verification; as you said, the equipment does not experience any internal pressure during lifting.
It only indicates that the software is not yet perfect, or that the calculation methods used by the software have a limited scope of application.
My personal opinion: Since the corner areas of the head represent points where the structure is discontinuous, the calculations for such heads are based on the assumption of a continuous rotational body. GB150 also does not recommend making openings in these corner areas, as the stresses in those regions are complex and lead to significant discrepancies compared to the assumptions used in the calculations. Therefore, as a precaution, it is standard practice not to perform any welding operations in these areas, which is also in line with logical safety requirements.