How to choose lugs for DN3200 horizontal tanks
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It is a horizontal storage tank made of stainless steel (304); the weight of the equipment is 9 tons, and the wall thickness of the tank body is 10 mm. The client now requires that lifting lugs made entirely of stainless steel (304) be added. According to the HG/T21574-2018 standard, how should plate-type lifting lugs be selected, and how should the calculations for verification be carried out?
The ear plate shape is as shown in the figure above: L weld length； Distance from the center of the H earpiece hole to the weld ； Distance from the center of the R earpiece hole to the edge of the critical section ； d Ear hole diameter ； h Weld height ； δ is the earpiece thickness. For 0–20 mmA3 steel, the tensile yield strength is 1 = 240 MPa, the shear yield strength is = (0.6–0.8)1, and the allowable stress for fillet welds is 2 = 120 MPa. The critical section is subjected only to shear stress, with the cross-sectional area A = (R – d/2) * δ (in fact, it can also be calculated as A = (2R – d) * δ) ； Shear stress τ = F/A, where F is the external load ； The design requirement is τ﹤/n, that is, F/﹤(0.6～0.8)1/n, where n is the safety factor and ranges from 1.6 to 1.8. The weld cross-section is subjected to stresses resulting from both shear and bending forces. The cross-sectional area of the weld, A, is equal to 0.7*2hL, where 0.7 is the reduction factor for the weld area ； The weld moment M is equal to F*H, where F is the external load ； The bending moment resistance factor of the weld cross-section is W=0.7*2HL2/6 ； The stress resulting from the combined action of shear and bending is σ = F/A + M/W ； The design requirement is σ﹤2, that is, ﹤2.
This is an example of strength calculation; by replacing the material allowable stress parameter for S30408 with that of A3 steel in the formula, it is possible to verify the strength of the lifting lugs.