limitation of slipon flange

[stesw90]

Dear All,
I have a 20" shell at the channel side of the heat exchanger for which i am using 600# slip on flange,
design pressure at channel side=1250psig / shell side=300psig
design temperature=185°f
MDMT=-45°f
finished thickness for the shell is 0.944" , hub thickness at small end of the flange is 0.875,
as per my knowledge we follow weld detail as per uw-21 ,
weld size we provide is 1.4*tn or the hub thickness which ever is less,
My concern is do we need PWHT and full radiography at this joint,
thickness of throat below 32mm so i don't think we need full radiography and PWHT,

I couldn't find any reason for the requirement since my design software is showing me this direction which i don't find relevant,

Regards,
stesw90

 

[SnTMan]

stesw90, you don't say what the material(s) is but, corner joints are not generally considered radiographable. For carbon steels P1, PWHT would not appear to be needed.

Regards,

Mike

 

[racookpe1978]

Your slip-on flange weld requirements should have an interior fillet weld AND an exterior fillet weld. Verify they are both made, both of the right material (rod and heat and filler and amperage) at the right pre-heat and are the right size. Dye pen or mag particle will be surface only.

 

[Duwe6]

". . .and are the right size."
as usual racookpe hit the problem item. To develop full strength in the Flange-to-Shell weld, the exterior fillet size* has to be 1.4 x pipe wall thickness. This makes the throat of that fillet the same thickness as the pipe wall. It looks huge to the welder, and a large percentage will stop welding several beads short of the minimum required size. While performing the PT/MT testing, please gauge that fillet size and make sure it meets minimum.

*for ASME items, the inner weld is considered a 'seal weld' only and you are not allowed to use its strength in the Design calc's.

 

[SnTMan]

Not a big fan of the recent UW-21 changes. Who knows the hub small end thickness in advance? Messy drawing note now.

Preferred the wall thk x wall thk scheme.

Regards,

Mike

 

[stesw90]

Thanks for everyone's reply,
I am using sa-105 slipon flange,
as in UCS-57 throat thickness is not exceeding 32mm for the requirement of full radiography nor equal to or exceeding 38mm for the requirement of PWHT,
but then too computer software is showing PWHT and 100% radiography requirement,
what i am concerned, is there any special requirement for slipon flange which i am not aware of or which i am missing in design,
or is there any special require for flanges above 300#,
though i have changed from slipon to WNRF but without a answer for a question, there is a good price difference betwen bot the flanges, hope i will find a clear answer with all of your help,
anyways thank you for replying,

Regards,
stesw90

 

[Duwe6]

". . . fillet welds with a throat thickness of 1⁄2 in. (13 mm) or less used for attaching
nonpressure parts to pressure parts provided preheat to a minimum temperature of 200°F (95°C) is applied when the thickness of the pressure part exceeds 1-1⁄4 in. (32 mm);"

PWHT is put into effect with a HUGE weld, not 'normal' sized ones. Recalc that flange-to-body joint. Try using a 3/8" fillet [gives a 0.265" throat, theoretically]

Stop believing everything you 'puter program tells you; ASME has never required RT of fillet welds. Until you can design 'by hand', it is not really safe or prudent to just put numbers into a program and believe anything it spits out.

 

[SnTMan]

Programmers. What can you say?

Regards,

Mike

 

[racookpe1978]

Yeah. Well, programmers actually think computers are accurate.

They are just a faster way to get an approximate answer, a wrong answer, or an answer to the question you did not ask nor needed answered. But they might be faster!

 

[GenB]

Computers are what you say, accurate, but to the point of what you feed them. When you set your programs be careful of "defaults", it will confuse you. It means that you told the computer to default to RT and PWHT and it gave it to you at the end... good luck

 

[stesw90]

Hmmm..

 

[MJCronin]

Isn't this action really a repair being made to an ASME VIII pressure vessel ?

Are the repairs being made by a firm holding an "R" stamp ?

MJCronin
Sr. Process Engineer

 

[stesw90]

no

 

[Shmulik]

stesw90:
Please be aware of Section II part A, SA-105 scope, 1.1: "Tubesheets and hollow cylindrical forgings for pressure vessel shells are not included within the scope of this specification".