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LARGE RADIUS BENDS

LARGE RADIUS BENDS

LARGE RADIUS BENDS

(OP)
In 30 odd years in petrochem, I have always understood that a 5D bend radius for example will be 5 x NOMINAL diameter.

In a currect job the CAD technician has based small diameter (2.5" nb) 5D bends on the ID ... honestly ... and the fabricator made the bends based on the OD. This means that nothing fits, and in my opinion is a cock-up all round.

Question ... Is there a formal (Code) reference to large radius bend identification being based on a multiple of the NOMINAL diameter out there ? I have not seen one.  

 

RE: LARGE RADIUS BENDS

I've never seen a code that specifies hot bend nomenclature.  For forged fittings, the code is clear, but for hot bends it seems to be up to the purchaser to be clear and the fabricator to follow the instructions.  My read has always been that they should be specified based on published OD of the pipe, but I've gotten them based on nominal ID.  Since I work outside of plant fences this has never been a problem for me.  I can see where it would be serious on a pipe rack.

It looks to me like a cock up all around.

David

RE: LARGE RADIUS BENDS

MIL-STD-1627B shows 5D - using Nominal Diameters!  A 5D bend of a 2" ND = 10"
 
Class WP fittings are manufactured to the dimensional requirements of ANSI B16.9 or ANSI B16.28 Class CR fittings are manufactured to the dimensional requirements and pressure ratings of MSS SP-43.
 

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/

RE: LARGE RADIUS BENDS

C2it:

BigInch nailed it.  According to AMSE 31.8 and 31.4, if it is, for example, a 20" pipe and you want a 5D; it is 20*5 for the radius in inches.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
 

RE: LARGE RADIUS BENDS

This sounds like another case where "the CAD technician" thinks he (or she) knows more than the trained piper.
I would suggest that you take the "CAD Tech" out behind the barn and give him an education.  I would reassign "CAD Tech" to a job where mistakes are not as costly until such time that he is properly trained in PIPING..   

RE: LARGE RADIUS BENDS

Dears,
Somehow for larger diameter piping 3.5 times the diameter should presumably give fairly long radius.
I recall someone visited during early 80's for our 18 Km long X-Country 6" dia pipeline while I worked at my previous employer used a 'Master caliber pig'. Who mentioned this figure for his caliber pig turning needs (probably Named Mr. Tom barker or so if my memory is correct?)
 

Best Regards
Qalander(Chem)

RE: LARGE RADIUS BENDS

True, but sometimes yes, sometimes no.  5D has a better probability of success with more/most modern instrumented pigs, but still a chance you could need larger than 5, plus there is a chance you can buy one off the shelf where a 3.5 would be special order and probably wouldn't fit in well dimension wise with any existing piping elevations that you might need to tie into.  5 is a safer bet all around.    

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/

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