Problems with the strength calculation documents for pressure vessels

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Strength calculation sheet: Regarding the strength calculation sheets for pressure vessels, the following issues may arise: 01 The material grades specified for the cylinder, head, etc. in the calculation sheet do not match those indicated in the drawings. 02 The input of design parameters in the calculation sheet does not match those shown in the drawings; factors such as the allowable stress of the material, corrosion allowance, nominal thickness, design temperature, material density, radial displacement at the shaft seal of the mixing shaft, tensile strength of the mixing shaft, curvature height of the head, structural parameters of the flanges and gaskets, and test pressure can all lead to errors in the design calculations. 03 For compressed components that cannot be calculated in accordance with standards such as GB150 and GB151 (such as rectangular tube sheets and flanged heads), no other calculation methods were employed. 04 For large mechanical mixing equipment, only internal or external pressure calculations are performed for the upper head, without taking into account the loads exerted by the frame. 05 The standard numbers of standard components are used for the manholes in the design drawings; however, the specifications for the manhole connections, gaskets, flanges, bolts, nuts, and manhole covers are different from those of the standards as stated in the general layout instructions. In such cases, it is necessary to draw diagrams of the manhole components and perform strength calculations on elements such as the manhole flanges and flange covers. 06 In the stability check of the external pressure cylinder in the calculation sheet, the value used for the calculation length of external pressure is incorrect; it is too small, failing to meet the stability requirements. 07 In the design calculation document, the reinforcement for some nozzle openings was not calculated ； The calculation for opening reinforcement of non-radial connections is carried out in accordance with the calculation method for opening reinforcement of radial connections ； The value of the weld area A3, which serves a reinforcing function in the reinforcement zone, does not match the value calculated based on the dimensions of the welded joint shown in the diagram ； A standard manhole was selected; the manhole cover has openings, but no reinforcement calculations for those openings were performed. 08 The acceptable grade for radiographic inspection of the welded joints of elliptical heads is Grade III, and the weld joint coefficient 1 in the strength calculation should be 0.85. 09 In the calculation of the heat exchanger tube sheet, incorrect values were used for the metal temperatures of the shell and the heat exchange tubes, resulting in lower differential stress. 10 The static pressure of the liquid column was not taken into account in the reinforcement calculation for the openings at the bottom nozzles of the spherical tank. 11 For vertical containers, ear-type supports are selected; if such supports are not available, selection calculations are carried out ； Vertical containers are equipped with supported Type B supports, and the allowable vertical load defined by the container head is not checked. 12 Containers equipped with safety valves – lack calculations for the discharge capacity of the safety valves and the safe venting capacity of the containers.