Hi, all,

How does CAESAR II calculate the bolting stress in the “Flange Leakage/Stress Calculations” module?
The bolting stress results from CAESAR II are much different as my calculation by hand. By comparing “flange.msg” file, I found two different points:

1. Bolting area Ab
I have 12 bolts with 28.5 mm (1.122 in), so total area is
Ab= pi /4 * 1.122² * 12 = 11.86 in²

However I got Ab= 8.74 in² in “flange.msg” file

2. Basic gasket seating width b0
Following are input values:
Facing Sketch - 6
Facing Column - 1
Nubbin Width - 0
Gasket Outer Diameter - 193.62 mm (7.623 in)
Gasket Inter Diameter - 159.78 .mm (6.291 in)
Based on ASME Sec. VIII, Div. 1, Table 2.5-2,
b0= w/8
Assumed w is calculated in Caesar from gasket outer diameter and inter diameter, so
w= (7.623-6.291)/2 = 0.67 in
then
b0= 0.67/8 = 0.083 in

However I got following results in “flange.msg” file
CONTACT WIDTH OF GASKET, N = 0.5831
BASIC GASKET SEATING WIDTH, b0 = 0.146

This looks like b0=N/4, which is however for Facing Sketch 3 and 5 in the Table 2-5.2.

Can anybody help me to explain this?

Thanks in advance

The quick answer to your question is 1.125" bolts have a root dia 0.963" when the threading is taken off. Use this to calculate the "core area" of the bolts and you get 8.740 in².
Without going into the "nubbin or serration" question your incomplete details raise other questions.
The 12no 1.125" bolts implies an 8" 600# RTJ flange.
Yet you give gasket diameters of 7.623" outer and 6.291" inner. From this the width is 0.666" [as you calculate] and a pitch 6.957" [the average].
When we look up in ASME B16.20 the nearest ring no is R-50 w 0.625" P 10.625". But an R-50 must be used with 8" 1500# where the bolts would be too small. I go through the same exercise with RX and BX rings both in B16.20 again but there is no match. It may be that the information you are inputting to the flange solver is doolaly [useless].