[Repost] Some changes in the HG/T2157-2018 lug standard

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The following is reprinted from the official account. 1) The comprehensive impact coefficient for lifting has been adjusted from 1.65 to 1.2 x 1.125 = 1.35. 2) A check for the squeezing stress in the eye bolt holes has been added; this squeezing stress is set at twice the yield strength (probably taking into account the increase in yield strength due to deformation) ； Pay attention to the dimensional fit between the eyelet holes and the pins. Pressure Vessel Design Manual (Fourth Edition) by moss: a factor of 2 yield strength is also used for the lifting lug holes. 3) Additional hook arrangements have been added, particularly regarding the installation and layout of hooks for horizontal containers ； The arrangement angles of the shaft-type lugs and the tail lugs. 4) The designer shall verify the strength and stability of each critical section during the lifting process (the calculation procedure is shown in Appendix C). Note that selecting standard lifting lugs only exempts the verification of stresses on the lugs themselves and certain parts of the housing. (5.1.3) 5) It should be specified that the designer must verify the strength and stability of the lug itself, as well as those of the lug and the gasket, the lug and the equipment head or cylinder section, and the gasket and the critical sections of the cylinder section. If these requirements are met, such components can be used directly. (5.1.2) 6) The gasket and the surface of the shell or head must fit tightly together, with a gap of no more than 1 mm. (5.3.1) 7) The shaft-type lug shims should be manufactured as single pieces; when joined together, no more than 2 pieces should be used, and the welding joints should be arranged evenly ； Furthermore, for the shaft-type lugs used in rolled steel plates, the butt joints must be inspected using 100% RT testing; they must meet the requirements of grade II as specified in NB/T 47013.2, with a testing technology level of AB grade (5.3.4, 5.4.2). (5.4.1) 9) The remaining stress-bearing welded joints must also undergo 100% MT/PT testing, with a grade of I required for acceptance. (Apart from the reinforcement plates inside the shaft lugs) (5.4.3) 10) Although it’s not a change, it’s worth noting that the weld leg height is 0.8S, rather than the commonly used 0.7S. 11) Based on the allowable stress of the material, four levels of 120 MPa, 140 MPa, 160 MPa, and 180 MPa are designated, and the appropriate value is selected by referring to a table. (B.1.4) 12) Requirements for gasket thickness: when the nominal thickness of the head or cylinder is less than or equal to 20 mm, the gasket thickness is the same as that of the head or cylinder; when the nominal thickness of the head or cylinder is greater than 20 mm, the gasket thickness is set at 20 mm. (B.1.5) 13) Appendix C has been added, which includes calculations and checks of the forces acting during the lifting of equipment: (1) Check of longitudinal bending stress. The value of A is consistent with that specified in the NB/T47041 standard for tower-type containers, namely A=0.188δ/Do; here, one uses the outer diameter and the other the outer radius. (2) The allowable axial compressive stress is also the same as that specified in the standard for tower-type vessels, min(B,) ； Personally, I think it’s too conservative because lifting is basically a one-time operation, and at least min(1.2B, ) should be used. The Pressure Vessel Design Manual (Fourth Edition) uses min(1.33B, ) ； The method used in GB/T 150 for calculating external pressures is inherently conservative; therefore, the value of B used to calculate the allowable axial compressive stress is also conservative ； A comparison of external pressure calculations will be released in a while. 14) Appendix D has been added, covering the support types for the inner ring of the equipment skirt and the relevant verification. It is not clear whether it is possible to select appropriate parameters and carry out calculations without using the GB50017 standard. The verification of the skirt base plate only states that the circumferential bending stress and compressive stress in the skirt base plate caused by the load from the tail lugs should also be checked. However, no specific calculation guidelines were provided, probably out of concern that doing so might exceed their authority and would require consultation with the standards for tower-type containers. 15) Control of local stress at the lifting lugs during lifting: the local film stress shall be ≤ 1.5 times the allowable stress of the material, and the stress resulting from the first and second lifting attempts combined shall be ≤ 2.6 times the allowable stress of the material (judged using the method specified in GB/T150). When calculating local stress when the standards are not met, care should be taken to keep the stress applied in one step and then the second step at 2.6 times the value; however, for the draft analysis and design documents, 3 times the value should be used. 16) Increased lifting capacity (e.g., the rear lifting lugs have been increased to 300 tons, the top lifting lugs to 15 tons, and the shaft-type lifting lugs to 300 tons). 17) The requirement regarding an increased length of the thickened section of the cylinder, which was criticized, has been removed; however, the extent of the changes is too great. It is still better to give suggestions and requirements, but they shouldn’t be as long as before. If anything is missing, feel free to add it.