18" B16.5 Blind flange needs drilled and tapped to accept a 1.5" PSV

[WeldEng0318]

Hi everyone,

I have class 300 18" blind flange bolted to a manway. We are proposing to do a 1.5" drill and tap and thread a PSV in. My assumption was to follow Table 6 and 8 but they are a bit confusing as to weather its allowed or not because i feel like its not really addressing my exact question? Any input would be appreciated

Thank you

 

[KevinNZ]

I assume you are referring to B16.5 table 6. This gives the smallest hole (attached pipe) that requires reinforcing. If attached pipe is smaller you can attached it without a flange hub or reinforcing

 

[LittleInch]

But only in the centre ...

There are many posts on this issue. Do a search.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[XL83NL]

At LI: iirc some time ago an interpretation was posted saying it may also be out of centre….

Huub
- You never get what you expect, you only get what you inspect.

 

[Cobra17]

here is the interpretation

 

[XL83NL]

Thanks. Exactly that one.

Huub
- You never get what you expect, you only get what you inspect.

 

[LittleInch]

Thanks, forgot about that one.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pmover]

Requesting some clarification here on this interpretation.

Question: The Interpretation does not "prohibit" an offset hole in blind flange. However, if the hole is offset, will the blind flange w/ fitting be considered altered and still need to be qualified per code?

Probably ought to be another thread?

 

[XL83NL]

As I read the interpretation, I don’t see how it requires additional consideration or qualification of any kind.

Huub
- You never get what you expect, you only get what you inspect.

 

[SnTMan]

Begs the question: How FAR offset?

Regards

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Cobra17]

I would say you can offset it as long as it meets note 1:

1) The hub dimensions shall be at least as large as those of the standard flanges of the size to which the reduction is being made, except flanges
reducing to a size smaller than those of columns 2, 4, and 6 may be made from blind flanges

so in other words, if you are reducing to a 1/2" NPS, X = 1.19 per table 8C, so as long as you have a 0.155" ((1.19-0.88)/2) to the nearest hub edge on a 150# hubbed blind, you are ok. If it's a standard blind, then as long as the reduction is within the pressurized diameter.