Pipe insertion depth ASME Section VIII Div 1 3

[NL8]

Does anybody happen to know the typical insertion depth of a 20" sch 10 pipe into a 20" slip on flange that would satisfy ASME SEction VIII, DIV 1?

 

[vesselfab]

I would really call it a set back from the face rather than a insertion length. Code requires weld with a throat of .7tn which equates to a leg length of nozzle wall, in round figures. Normally you would set the end of pipe back from the face tn plus 1/8" netting a 1/8 clearance between weld toe and corner of flange bore/face. The maximum set back is tn plus 1/4"

see section viii div 1 appendix 2 fig 2-4 (3)

 

[SnTMan]

See also UW-21(b).

Regards,

Mike

 

[NL8]

Thanks VF, that was just the information that I didn't stand a chance of getting as we don't have a copy of Sec VIII on the shelves here.

 

[pingmi]

VesselFab,

Would you please help me understand why are these clearances required and how did they arrive at these figures (example:
'1/8 clearance between weld toe and corner of flange bore/face'.

Thanks in advance.

 

[vesselfab]

why is the sky blue?

just the rules

It is nice to have the clearance so you won't damage face while welding

 

[davefitz]

pingmi:
The 1/8" clearance is to allow thermal expansion of the branch during welding, so that hot cracking of the weldment or developing residual stresses does not occur.

 

[pennpiper]

Let's go back to the original question. The question concerned the "insertion depth of a 20" sch 10 pipe into a 20" slip on flange."

A slip-on flange is attached to the pipe with two 45 degree bevel welds. The one weld is on the out side of the pipe at the back of the flange hub. The other weld is on the inside of the flange (behind the flange face) attaching the end of the pipe to the inside of the flange.

The dimension for the height of both 45degree bevel welds is to be equal to the thickness as the pipe wall. The 1/8" clearance is to allow for a little tolerance for the welder and prevent weld spatter from damaging the flange face.

So the answer is: Insert the pipe into the slip-on flange only far enough to allow distance from the end of the pipe to the face of the flange equal to the thickness of the pipe wall plus 1/8"