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1. Why should the flange bolt holes be evenly distributed across the center? 2. How should the thickness reduction rate of the head formation be considered? Is it related to the material? 3. Why is Pc≤0.4［б］φ and K≤1.5 specified? 4. The static pressure of the liquid column is less than 5% of the design pressure, so it can be ignored – why? 5. What are the differences in the calculations for thick-walled and thin-walled cylinders? 6. How are the test pressures for horizontal and vertical towers and vertical vessels calculated? How is the pressure of the water column taken into account? 7. Should the execution standard for vertical containers specify reference to NB/T47041-2014? 8. The technical grades for radiographic inspection are mostly Grade AB, while those for ultrasonic inspection are Grade B; for important equipment, the radiographic inspection grade is B and the ultrasonic inspection grade is C. For the material 15CRMoR specified in the drawings, is it incorrect to raise the inspection technical grade? Ultrasonic inspection of steel plates generally meets Grade II standards – is it incorrect to raise the grade for 12CR2Mo1R to Grade I? 8. The drawing indicates the maximum allowable operating pressure; is it necessary to install a safety valve? Is this related to the airtightness test? Or? 9. For spherical heads, it is generally not stated at the beginning that GB/T25197-2010 should be followed, right? Should I write it or not? There are so many pictures I’ve seen that I don’t write about them
1. The mid-span not only ensures even stress distribution on the fasteners but also facilitates operation. For the flanges on the vertical vessel shell, this arrangement also prevents leakage from causing the fluid to reach the fasteners and thereby corrode them. 2. The forming thinning amount is mainly to facilitate manufacturing and cutting. Due to the existing head standards and the definitions and references for a thickness of 150, although a reduction amount is specified, disputes still arise in design and manufacturing at times. According to the standards, the thickness reduction depends only on the shape, diameter, and thickness, and not on the material. 3. The range is limited because the formula is derived from the mean diameter formula; this formula assumes that the container is a thin-walled one, which is why such a constraint exists. 4. This should be engineering experience, I guess. 5. Thin-walled containers are subject to membrane stress according to the moment-free theory, with only two-dimensional stresses considered ； The theoretical basis for thick-walled vessels is the Lame formula, which takes triaxial stress into account. The distinction between thick-walled and thin-walled can be simply made using K=1.5. ≤1.5 is thin-walled, and the opposite is thick-walled. 6. The hydrostatic test pressure is calculated using a formula. When changing it to a horizontal configuration, the hydrostatic pressure of the liquid column in the vertical position must be taken into account. The height of the liquid column here can be taken as the maximum height of the liquid column when it is fully filled (not the maximum height of the device). It should also be noted that the hydrostatic pressure of the liquid column here must not be confused with that at the point of calculation; when the hydrostatic pressure corresponding to the calculated pressure is less than 5%, it can be ignored, whereas the hydrostatic pressure of the liquid column at the hydrostatic test pressure cannot be ignored. 7. There is no need to specify tower standards; using conventional standards such as 150 is sufficient. 8. The standards and specifications set out the minimum requirements. Designers have the right to raise design and manufacturing requirements. 9. The presence of a MAWP does not necessarily imply the need for a safety valve or a gas-tightness test. Current domestic standards stipulate that when a safety relief device is present and a gas-tightness test is conducted, the MAWP must be specified, primarily to prevent the safety valve from activating during such tests. 10. Doesn’t GB/T25198 already specify hemispherical heads? It can definitely be mentioned. Perhaps due to the inconsistent thicknesses of the cylinder and the hemispherical head, a certain design was adopted that results in a head that is not standard hemispherical in shape; that’s why they don’t specify it – as long as a part diagram can clearly illustrate it, that’s sufficient.