App 2 Loose flange and host setback distances

[michigander]

I have an App 2 loose flange that is 3" thick per design that attaches to a 1/2" thk head using 1/2" fillet welds on both sides of the flange. I had asked the fabricator to purchase a head with a 3" straight flange, but the head was ordered with only a 1 1 2/" straight flange. Using a normal setback for the inner fillet weld causes the head to be down into the flange too far making the outer fillet to be more like a giant groove weld. The fabricator wants to set the head back into the flange by 1 1/2". This would keep the relationship of the flange and head more normal at the backside of the flange, but now I don't have a normal setback from the face of the flange. Are there any rules tha specifically address this setback distance?

Thanks in advance,

Michigander

 

[pennpiper]

You appear to be trying to apply the general rule for a "Slip-On" Flange used with pipe or piping fittings to your unique situation. That is wrong.

I suggest you listen to your fabricator.

 

[vesselfab]

well hold on a minute

appendix 2 has rules

look at figure 2-4 page 350 of 2007 issue

says max set back is c+1/4"


if you are trying to save the head....fabricate and weld on a 1-1/2" to 2" long pup and weld to heat to simulate a 3"+/- sf. fully radiography the long seam and girth seam just so there is no questions asked later

 

[82253]

ASME Section VIII Appendix 2 address this setback, max setback in your case would be tn= 1/2" plus 1/4" = 3/4".
Fabricator needs too add short cylinder to vessel head then attach body flange. Steve

 

[michigander]

Thanks so much. I can't believe I missed that in App 2.