Dear Duane,
The bolt correction factor is to account for bending of the flange in between the bolts. If the bolts are too far apart, then the flange face in between the bolts (in circumferential direction) can open up and cause leakage.
This is per RCB-11.2 in the TEMA standard. In the program if the circumferential bolt spacing is more than that suggested in the TEMA std., then the flange moments are multiplied by this factor. Thereby, increasing the flange thickness and as a result making it stiffer.
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Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM