vtrompg
Mechanical
- Oct 23, 2013
- 2
The vessel in question is a 2003 U-2 stamped vessel with a 30" pad-type flange on the top head (for clarity, the nozzle configuration is as per Fig UG-40(a-2) in Div 1). This flange has been problematic during past maintenance activities and as a result some holes have been re-drilled larger and re-threaded.
With these holes drilled larger the question is being asked as to how large the holes and bolting can go and still remain Code compliant? The connecting flange is not the limiting component in terms of nut access - it is a modified flat cover designed in accordance with ADM so nut access is not a problem. I have not dealt with pad-type flanges in the past, and from what I can see opening reinforcement is required (AD-520) and the depth of the holes is limited (AD-740) - both references are from ASME VIII Div 2 2004.
So is there a limit on the bolt diameter? How are bolting requirements determined/checked with pad-type flanges?
With these holes drilled larger the question is being asked as to how large the holes and bolting can go and still remain Code compliant? The connecting flange is not the limiting component in terms of nut access - it is a modified flat cover designed in accordance with ADM so nut access is not a problem. I have not dealt with pad-type flanges in the past, and from what I can see opening reinforcement is required (AD-520) and the depth of the holes is limited (AD-740) - both references are from ASME VIII Div 2 2004.
So is there a limit on the bolt diameter? How are bolting requirements determined/checked with pad-type flanges?
