Multiple holes in blind flange - alternative to calculation?
Multiple holes in blind flange - alternative to calculation?
(OP)
My company utilizes blind flanges frequently in multipoint thermocouple assemblies designed to ASME BPVC SECTION VIII, DIV.1. Frequently these blind flanges have multiple holes drilled through them in circular patterns around the flange center. Calculations are typically done per UG-39 to determine flange thickness.
ASME B16.5, Table 6 shows single, centered hole size limitations in blind flanges without requiring a hubbed flange. Hubbed flanges in the case of a slip-on flange have a hole through the center the size of the pipe OD that the flange is designated for.
Rather than doing UG-39 calcs, is it allowable to determine whether the holes drilled in our flanges are fully circumscribed by either this minimum allowable diameter hole for the standard blind flange or by the pipe OD of the hubbed flange, and if so, to use the flange as directed per ASME B16.5?
I have seen this proposed as a practical approach to flange analysis by a well known member of this forum in another thread, but I have not seen any indication in the code or related documents that explicitly allow this.
Thanks,
Tim
ASME B16.5, Table 6 shows single, centered hole size limitations in blind flanges without requiring a hubbed flange. Hubbed flanges in the case of a slip-on flange have a hole through the center the size of the pipe OD that the flange is designated for.
Rather than doing UG-39 calcs, is it allowable to determine whether the holes drilled in our flanges are fully circumscribed by either this minimum allowable diameter hole for the standard blind flange or by the pipe OD of the hubbed flange, and if so, to use the flange as directed per ASME B16.5?
I have seen this proposed as a practical approach to flange analysis by a well known member of this forum in another thread, but I have not seen any indication in the code or related documents that explicitly allow this.
Thanks,
Tim





RE: Multiple holes in blind flange - alternative to calculation?
RE: Multiple holes in blind flange - alternative to calculation?
I would
1. regard the outside of the ring of holes as the diameter of a large hole in the flange and use this see whether you can use a bind flange or a full hub per B16.5. This will mean the flange is thick enough for bolting stresses.
2, use FEA or other method to calculate the stresses between the holes. Design to ASME VII div 2.
RE: Multiple holes in blind flange - alternative to calculation?
I see no way that additional material within what would otherwise be a void in the center of the flange would be detrimental to the flange seal.
RE: Multiple holes in blind flange - alternative to calculation?
RE: Multiple holes in blind flange - alternative to calculation?
You can of course run the UG-39 calculations.
Another way to do this is to consider it as a loose ring flange as per Appendix 2, the ID being equal to a circle circumscribing your hole pattern. B16.5 thickness may or may not be adequate, as Apx 2 calculations of B16.5 flanges are known to be troublesome.
None of these methods will consider detailed analysis of the stresses between the holes, etc.
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Multiple holes in blind flange - alternative to calculation?
I also would consider the design as described above using the hubbed flange adequate. I frequently have to submit my calculations to a third party for review if it is a PED or a U-stamp job, so I need to be able to convince them and the AI that my use of a hubbed blind flange for this application is acceptable per ASME BPVC Section VIII, Div.1, hence the reason for my post. It would help us in sourcing materials if I could specify a hubbed blind rather than a custom blind flange.
RE: Multiple holes in blind flange - alternative to calculation?
Note that we have previously confirmed that reducing socket-welding and threaded flanges are indeed machined from hubbed blinds, rather than being pierced during the forging process.
RE: Multiple holes in blind flange - alternative to calculation?
We design most our jobs in compliance with PED. Typically the blind flanges dont fall into a category, and therefore using tbale 6 is sufficient.
RE: Multiple holes in blind flange - alternative to calculation?
moltenmetal, when you use the term "we", you wouldn't be referring to the ASME BPVC code committee, would you?
RE: Multiple holes in blind flange - alternative to calculation?
RE: Multiple holes in blind flange - alternative to calculation?