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Opening on Blind Flange 2

MizanAMC

MizanAMC

Mechanical
Apr 28, 2024
17
Hi all, currently im designing a blind flange (28") for an LPG storage tank based on the asme sect 8 Div 1.
The blind flange had two threaded opening, 2" npt and 1-1/4" npt. Based on UG-36, i understand that this size of opening do not required reinforcement calc. Does this mean that i can just proceed this opening on the ANSI 300 28" blind flange?

Hope someone can help me on this. tq
 
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UG-39(a) addresses opening in flat heads. This does reference the rules in UG-36(c)(3) for opening size and spacing limits.

If you meet these size and spacing limits then the blind flange does not need to be reinforced for these openings.
 
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I would no longer call this a blind flange...now is a bolted cover and needs to be designed to UG-34.
 
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Geoff13 said:
UG-39(a) addresses opening in flat heads. This does reference the rules in UG-36(c)(3) for opening size and spacing limits.

If you meet these size and spacing limits then the blind flange does not need to be reinforced for these openings.
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hi geoff13, can u see this paragraph that i found from Asme interpretation database, what is "additional design calculation" refers to?
 

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It's telling you exactly what I said...it's no longer a blind flange. Even though the openings are exempt from reinforcement it needs to be calculated per UG-34. You can't use the pressure/temp ratings of B16.5 or B16.47.
 
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There are times when I wish the Code Committee would explain their response, not just yes or no.

I have re-read the Code and I can't see where the Committee is finding this requirement. It seems to me that they've added a requirement that isn't actually in the Code.

Nonetheless, UG-34 is quick and easy so not much trouble to add to the design package.
 
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The Code allows B16.5 flanges to be used at the pressure/temp ratings of those standards without additional calculations. B16.5 allows reducing flanges. Multiple openings do not meet B16.5 and therefore cannot be used as such. Therefore, UG-34 is required.
 
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This sort of question appears many times on ET and also whether you need to have the hole in the dead centre of the blind flange.

The code writers for PVs know that using / allowing standard components is needed, but they don't want people going around doing modifications to them.

Designing a flange or blind to ASME VIII always leads to the item being bigger and heavier. but that's the rules for PV's

Oh and flanges stopped being "ANSI 300" about 50 years ago. They are ASME B 16.5 / 16.47 class 300 flanges. (not lb or # or anything else, but "class 300".) Always best to be precise in these things....
 
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David3399 said:
The Code allows B16.5 flanges to be used at the pressure/temp ratings of those standards without additional calculations. B16.5 allows reducing flanges. Multiple openings do not meet B16.5 and therefore cannot be used as such. Therefore, UG-34 is required.
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if im using UG-34(c)(2) Eq (2) to calc this bolted cover thickness, does this means that the number or size of the opening will not affect the thickness? since the opening dimension were not considered in the formula.

Thank you for your insight David.
 
Last edited:
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LittleInch said:
Oh and flanges stopped being "ANSI 300" about 50 years ago.
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oh thats new to me. haha. My company also practice using ASME b16.5 and class so on, since our client consistently refers to ANSI, I prefer to use the same terminology to avoid potential confusion.

but thank you for this ;), i might telling my client the same thing later :0 haha
 
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Correct. Opening size and spacing limits of UG-36 apply or use UG-39 for reinforcement.
 
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Zan00 said:
oh thats new to me. haha. My company also practice using ASME b16.5 and class so on, since our client consistently refers to ANSI, I prefer to use the same terminology to avoid potential confusion.

but thank you for this ;), i might telling my client the same thing later :0 haha
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Actually only 30 years ago.....

From the foreword of ASME B 16.5

"In 1982, American National Standards Committee B16 was reorganized as an ASME Committee operating under
procedures accredited by ANSI. The 1988 edition of the Standard extended nickel alloy ratings to higher temperatures,
clarifying flat face flange requirements, and included other minor revisions. The Committee determined that any metric
standard for flanges would stand alone, with metric bolting and gaskets; hence, metric equivalents were deleted.
Following approval by the Standard Committee and ASME, approval as an American National Standard was given
by ANSI on April 7, 1988, with the new designation ASME/ANSI B16.5-1988.
The 1996 Edition allowed flanges marked with more than one material grade or specification, revised flange facing
finish requirements, revised pressure–temperature ratings for several material groups, added a nonmandatory quality
system annex, and included several other revisions. The 1996 Edition was approved by ANSI on October 3, 1996, with the
new designation ASME B16.5-1996"

The official use of lb or # stopped in 1973 to be replaced by "class", but that still doesn't stop people using it to this day....
 
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LittleInch said:
The official use of lb or # stopped in 1973 to be replaced by "class", but that still doesn't stop people using it to this day....
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David3399 said:
Correct. Opening size and spacing limits of UG-36 apply or use UG-39 for reinforcement.
Click to expand...
Thank you guys for all the valuable insight. much appreciate it.
 
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