Is tapping the blind flange allowed offset to the centreline? This is for connecting a level controller. Not able to see any specific restriction in the code for tapping offset to the centreline. Can anyone please advise?
When you put a hole in the center of a blind flange, it is in effect a reducing flange. This is covered by B16.5 2009 in Table 6 on page 70. Depending on the sizes, you may need a hub (i.e. reinforcement) or you may not.
Now, when you put the connection in an off-center position, you no longer have a component which complies with B16.5. If you are dealing with an ASME VIII vessel or piping which allows the use of B16.5 components without calc's, then you are no longer in compliance since you no longer have a B16.5 component.
So... you need to now treat this blind flange as a flat cover per (I'm assuming) VIII Div. 1 UG-34. Calculate the required thickness (a B16.5 flange may fail this calc). Then use UG-39 for area of reinforcement calc's. Note the reduced requirement for area required vs what's required for shells and heads.
No. The exception you note is for cylindrical or conical shells or formed heads only. And that would include up to 3 1/2" finished opening diameters in some cases. NPT is not the criteria.
See UG-36(c)(2)(b) which sends you to UG-39 for flat heads - no exceptions.
Not entirely. UG 39(a) adds the span restriction to the diameter which might qualify for excemption.
If you're adding a 3" XXS nozzle with a finished opening of 2.3", you would have to ensure that the diameter of the blind is at least 10".
If you're adding a 4" Sch 160 nozzle with a finished opening of 3.438" then you'd need a blind with a nominal diameter of at least 13.75" to qualify for the excemption.
Right, jte. But those are exceptions, of which you noted were none in your previous post. Please see my '...for the appropriately-sized opening' comment.
I apologize if my lack of capitalization offended you.
Thanks for clarifying.
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Fitter, happier, more productive
So there you have it engrom. By my interpretation:
UG-34 allows for B16.5 blinds to be used as flat heads. UG-39 allows for openings in flat heads. UG-39(a)refers you back to UG-36(c)(3) for what is most likely the size of your opening, less than 2-3/8 NPT: no reinforcement other than that inherent in construction is required.
As you mention that is it offset, just be sure that you don't come too close to the edge of the head (See UG-39(b)(3). This requirement is buried in the text for multiple openings, but by my interpretation, and by lack of being mentioned elsewhere, I believe this applies to you.)
Hope my inconsistent capitalization didn't confuse you. Ha.
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Fitter, happier, more productive
The use of a B16.5 blind without thickness calculations is allowed by UG-11 and U-3. [Check the edition of B16.5 that you are using. Yes, the ratings change on occasion.] However, once you put the offset hole in it, it ceases to be a B16.5 component.
This leads to calculating the thickness per UG-34. I don't disagree that UG-34 allows B16.5 blinds to be used as flat heads. However, you must calculate the thickness rather than go by flange rating.
As for reinforcement, be sure to meet the diameter requirements of UG-39(a) prior to heading to UG-36.
Ah, jte. I see your logic regarding the transition of the blind from B16.5 to a flat head. I guess i was ignoring that strict delineation by clinging to the re-direct to UG-36.
I'll tell you what, I don't know about the rest of the world, but it sure feels like that (those) Friday beer(s) should be here by now. It's been a long one.
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Fitter, happier, more productive
![[cheers]](/data/assets/smilies/cheers.gif "[cheers] [cheers]")
