Determination of the number of flange bolts
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When using SW6 to calculate flat covers, I often encounter situations where the bolt spacing is too large and the calculation fails. However, looking at GB/T15-2011 7.5.2.1, page P193, it states that \"the maximum bolt spacing should not exceed a certain value\" – it refers to a recommendation rather than an absolute prohibition. So, is it acceptable to use fewer bolts? There are no issues in actual use, but the calculation report just doesn’t pass. I hope someone knowledgeable can help me out. Thank you!
It should not be a recommended value; if it shouldn’t be, then it cannot be executed, as the software may set it as a mandatory value.
The bolts are missing; the flange needs to be thickened, otherwise it won’t pass inspection.
Why is it required (recommended) that the maximum spacing not exceed a certain value? This is because it takes into account preventing uneven deformation in the unstressed areas of the flange or flange cover when the bolts are tightened, thereby avoiding potential leakage risks. The general approach is to try to meet the standard requirements; considering reducing the diameter of the bolts while increasing their quantity……
Standard pipe flanges may encounter issues where the calculations do not pass, but those are standards based on experience, so it is possible to ignore such calculations. For custom-designed flanges, it is advisable to ensure full compliance with the design standards
The bolt spacing exceeding the standard recommended values indicates that the design pressure and temperature, as well as the bolt diameter or material, were not optimized to the fullest extent
The most typical example is the use of large-diameter, high-strength bolts for low-pressure equipment; such bolts can provide a load capacity that far exceeds the required pre-tensioning force
Furthermore, generally speaking, there should be no deficiencies in the strength calculation report; if any exist, they need to be corrected along with appropriate explanations provided
By using bolts of a smaller size and increasing the number of bolts, the bolt spacing can be reduced.
Unless standard flanges are used, that means it is not advisable; it should rather be avoided