What is the relationship between the number of flange holes and the engineering pressure of the flange?
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What is the relationship between the number of flange holes and the engineering pressure of the flange? This post was last edited by bingyu252 on 2009-2-3 11:17 ]
The flange mainly considers the stiffness deformation, and the bolts are there to prevent it from stiffness deformation. I will not count the number of openings specifically. Try to choose standard ones (non-standard ones are similar), because standards have been verified in practice.
According to the standards, flanges with large pipe diameters and high pressures have many bolt holes. I don’t know what the specific relationship is. Usually, I just choose from the standards according to the working conditions.
The larger the flange, that is, the larger the diameter, the more bolt holes the flange has. This is because the flange will deform under pressure. The larger the flange, the worse the stiffness, and the greater the possibility of deformation. Therefore, more openings are needed to fix it, thereby limiting the deformation of the flange.
I don’t know about this, but there are more bolt holes with higher nominal pressure. I haven’t researched it yet. When using it, I just check the European standard part of HG20592.
Agree with what you said above. The greater the nominal pressure or the larger the nominal diameter, the greater the number of bolts. This is mainly to ensure the safety and stability of the work. The specific number of bolts for what pressure should be based on specific standards, not based on feeling or experience. The standards are based on long-term experience and scientific results.
"Calculation of flange bolt hole spacing" This problem is actually part of a structural optimization problem. Whether it is a flange or a flat cover, we always simplify the bolted connection structure into a simply supported model when performing calculations. The minimum wrench space given in the GB150 "Steel Pressure Vessel" specification is for a specific flange or flat cover. When you reduce the outer circle of the flange or flat cover and the size of the bolt circle, the thickness of the flange or flat cover becomes thinner. At this time, if you still use the original bolt diameter and spacing, it may not be able to seal (the reason is that the stiffness has changed. Flange leakage is actually partly caused by the insufficient stiffness of the flange plate. When the flange thickness is constant, the stiffness of the flange plate can be improved by adjusting the bolt spacing). In this case, the distance between the two bolts needs to be recalculated according to the simply supported model. The deformation of the flange or flat cover between the bolts is controlled by 1/1000. As the distance between the bolts becomes smaller, the diameter of the bolt will naturally become smaller. We have used this method in a large number of flange optimizations and achieved satisfactory results.
The higher the pressure, the thicker the flange and the greater the number of bolt holes. For details, please refer to the standard HG20615, Table 7.0.1-1, Table 7.0.1-2, for the specific number of bolt holes corresponding to the pressure level.