staggering of flanges

sharjeelfaiz · **Joined:** Mon Oct 15, 2007 6:54 am **Posts:** 128

Hello.

What is the reason for staggering of flanges ( in case of nozzles) and base plates ( in case of skirts)? Is it because the moments are less?

I really appreciate your answers.

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 657

sharjeelfaiz wrote:

Hello.

What is the reason for staggering of flanges ( in case of nozzles) and base plates ( in case of skirts)? Is it because the moments are less?

I really appreciate your answers.

Convention only. In my opinion.
Mauro

amol · **Joined:** Mon Sep 01, 2008 2:40 pm **Posts:** 64

I BELIEVE THAT U WANT REASON OF
WHY BOLT HOLES OF FLANGES ARE NOT DRILLED ON PRINCIPAL CENTRE LINE

sharjeelfaiz · **Joined:** Mon Oct 15, 2007 6:54 am **Posts:** 128

No. Its not like that.

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 657

sharjeelfaiz wrote:

No. Its not like that.

So, please explain, because i thought this was your question.
Mauro.

sharjeelfaiz · **Joined:** Mon Oct 15, 2007 6:54 am **Posts:** 128

Hello again.

My question is whether "staggering" of flanges is a requirement of some code. I also feel it is more of a convention, but had to get this point clear. Sometimes while coordinating a team of draftsmen, I have to face this situation, when I cannot justify a practice followed. I hope you all do too.

Any way, I really appreciate your answers. Thank you very much.

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 657

I understand you mean holes straddled on main axis (the axis passes between two adjacent bolt holes at the same distance to them).
Staggering of flanges is not an ASME Code Sect.VIII/Div.1 or 2 or 3 nor a Sec. I requirement. API valves have the same requirement of straddled holes.
I doubt there could be any Construction Code requiring it.
Mauro

sanjeev_shukla70 · **Joined:** Wed Apr 18, 2007 2:05 pm **Posts:** 260

Do not really understand what you mean by staggering of flange but straddled of bolt holes to the main axis is a convention followed for the fabrication purpose so that bolt holes on all the flanges/ valves etc are in the same orientation.

sharjeelfaiz · **Joined:** Mon Oct 15, 2007 6:54 am **Posts:** 128

I am sorry, i should have used the words "bolt holes should straddle the principal center lines".

Any way you all were right in judging my intention. Thanks again.

akonrad · **Posted:** Wed Dec 03, 2008 5:37 pm

Quote:

I doubt there could be any Construction Code requiring it.

TEMA?

PS the reason is that in case of leak, there is less chance for the medium to be in contact with bolts, possibly protecting the flanged joint from rupture, especially in remote locations (like pipelines), where inspection cannot be frequent. I saw a lot of heavilly corroded flanged joints because of a small and overlooked/ignored leak- some bolts were corroded thru in cases where the medium was dripping on a bolt, which was just under the center of the flange (either a badly welded flanges or distorted/rotated pipeline).
Sharjeel, I would strongly discourage you from experimenting, in case you can't find a good reason for this.

sharjeelfaiz · **Joined:** Mon Oct 15, 2007 6:54 am **Posts:** 128

Thank you very much for your reply.

I value your advice, Akonrad.

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 657

akonrad wrote:

Quote:

I doubt there could be any Construction Code requiring it.

TEMA?

PS the reason is that in case of leak, there is less chance for the medium to be in contact with bolts, possibly protecting the flanged joint from rupture, especially in remote locations (like pipelines), where inspection cannot be frequent. I saw a lot of heavilly corroded flanged joints because of a small and overlooked/ignored leak- some bolts were corroded thru in cases where the medium was dripping on a bolt, which was just under the center of the flange (either a badly welded flanges or distorted/rotated pipeline).
Sharjeel, I would strongly discourage you from experimenting, in case you can't find a good reason for this.

BRAVO Konrad.
Mauro

Ballbearing · **Posted:** Thu Dec 04, 2008 7:52 am

Hello guys,
ASME B16.5 Section 6.5 "......Bolt holes shall be equally spaced and pairs of bolt holes shall straddle fitting centre lines."
Regards,
BB

akonrad · **Posted:** Thu Dec 04, 2008 11:51 am

Just being picky... is B16.5 a construction code?

Ballbearing · **Posted:** Fri Dec 05, 2008 1:49 am

Hi Akonrad,
It was never my intention to suggest B16.5 is a Code. Mauro mentioned that he felt it was a convention and I was just posting a standard that references it.
However, it is a requirement of ANSI/AWWA C110/A21.10 - ANSI/AWWA C153/A21.53 and ASME PCC-1. (No Codes, just 2 x Standards and 1 x Guideline)
ASME VIII Div 1 has numerous references to B16.5 and if you are using flanges manufactured in accordance with B16.5 would you not have to comply with the rules outlined in B16.5 ?
B16.5 states bolt holes shall straddle the centreline, not should. Does this mean it is mandatory ?
I realise there is no code requirement but if a code references a standard does that make it mandatory ?
Regards,
Ballbearing

staggering of flanges

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