Flange design
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Based on the calculations for integral flanges per GB150, when the pressure and the center distance between bolt holes remain constant, the greater the allowable bolt load, the thicker the flange becomes. What is the principle behind this? Can bolts with a low allowable stress be used in calculations while actual use requires a higher allowable stress?
This is how I understand it; I’m not sure if it’s correct, but you can use it as a reference. Using a higher allowable stress will definitely reduce the cross-sectional area of the bolts, which in turn increases stress concentration in the flange area and thus leads to an increase in the flange thickness. Using larger bolts with a lower stress level wastes the performance of those bolts, as to meet the strength requirements and the forces acting on the flange, the bolt specifications required must not be lower than those calculated using a lower allowable stress
When the center circle of the bolt and the number of bolts remain unchanged, (under pre-tensioning conditions) the higher the allowable stress of the stud, the greater the design load on the bolt, which in turn results in a larger bending moment acting on the flange. This leads to a chain reaction of axial, radial, and circumferential stresses.
The 3rd floor is correct; the bolts, gaskets, and flanges are all coordinated as a whole. There is a significant risk with bolts that use a low allowable stress value in calculations but a high actual allowable stress in use, unless a predetermined bolt tightening torque is specified and a torque wrench is used for tightening.
The 3rd floor is correct; the bolts, gaskets, and flanges are all coordinated as a whole. There is a significant risk with bolts that use a low allowable stress value in calculations but a high actual allowable stress in use, unless a predetermined bolt tightening torque is specified and a torque wrench is used for tightening.
It can be understood that when the flanges are in flat surface contact, and with the center distance and cross-section remaining unchanged, using bolts with a higher allowable stress instead of those with a lower allowable stress mainly results in a waste of the bolt’s performance. When the flange is convex, that is, when the bolt surfaces do not make contact, the maximum allowable stress for bolts may lead to deformation of the flange due to excessive pre-tensioning, thereby affecting safety in use
The key is to choose the right gasket; there is a significant difference between non-metallic gaskets and wound gaskets Y, and flanges tend to deform during pre-tightening, leading to seal failure