Standard Blind Flange permissible opening

As per,


Interpretation: VIII-1-01-105
Subject: Section VIII, Division 1 (1998 Edition, 2000 Addenda); UG-34 and UG-39
Date Issued: December 7, 2001
File: BC01-336

Question: A circular blind flange, used as an unstayed flat head, has a nozzle attached at its
center using a full penetration weld, or a partial penetration weld, or a screwed connection. Are reinforcement calculations per UG-39 of Section VIII, Division 1 required for this geometry if the opening in the blind flange is of a size that is permitted in the flange standard referenced in UG­34(c)(1)?

Reply: No.


Can you say that what is the permissible opening diameter for the standard blind flange of size 24"x300# having MOC : SA 105 ????

Hi Ketan,

According to ASME B16.5 2003, Table 6, column 6, ASME allows a maximum 3.5" opening (< 4") at center of 24" std blind. This B16.5 coverage will help to skip calculation of blind thickness as well as reinforcement of opening on blind.

From 4" opening onwards, hub requirement will be started (need compliance to hub diameter X), become a flange rather than blind.

Please read footnote 1 for explanation.

Wish this help.

S K Tan

Hi Ketan,

Not sure previous post helps?

I supplement further on the hub diameter X.

If need to apply hub due to bigger opening size, designer only need to comply to the target size (4" as example) rather than the source size (24").

Above is concept of Reduction Flange per Section 6.8, B16.5.

Rgds.

S K Tan

SK Tan,

I think What you are talking about is for threaded blind flange.

Mukesh

Hi Mukesh,

Yes, I am quoting the reference as you said.

It shall cover nozzle opening (nominal pipe size) on blind, supported by Interpretation: VIII-1-01-105 which Ketan posted above.

Thank you!

SK Tan