Blind Flange Tap 2

[sandypiping]

I believe its a common topic and there are few threads addressing this.
I have a scenario where we need to have 1.5" tapping on a 3" blind flange. As per Table 6, ASME B16.5, we can go up to 1.25". My question :

1. What does 'smallest Size of reducing outlet requiring hub flanges' mean? Why smallest? Means for 4", can we go for 2" outlet for hub flanges? Or is it the other way round?
Blind flange doesn't have much hub...however, the figure shows tapping on blind flange as well
2. If 3" x 1.5" is not allowed, how we can justify with calc or addl reinforcement/gusseting? Should we expand to 4" to have 1.5" drain or request to change the drain size to 1" for 3" blind flange?

 

[LittleInch]

The wording is a little convoluted alright, but note 1 and the examples make it clear.

1 - This means that this is the smallest size at which you require a hub type reducing flange. BELOW this size you can drill and tap the flange if you've got sufficient thickness of flange as per figure 11.

So your post is not, IMHO, correct. As per table 6 the LARGEST hole you can drill and tap into a normal 3" blind flange is 1", not 1.25"

2 - You might be able to do some analysis or calculations but not to ASME B 16.5 you can't
If you want to tap and screw in your 1.5" pipe then to be in line with ASME B 16.5 you need to have a 6" flange.

Or 3. Just buy a 3" X 1.5" reducing hub screwed flange.

4 Use a 1" pipe as the connection on the 3" blind flange then screw on a 1.5" x 1" reducing coupler.

5 Use a 3" pipe welded or screwed to a 3" flange then weld or screw on a 3" x 1.5" reducer

Many ways to get the same result

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

 

[sandypiping]

Thanks LittleInch, appreciate your clarification. i was confused with the 'Smallest Size...' sentence