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I LUV NH3
08-01-2007, 04:22 PM
Howdy all,

I have just finished reading ASME B31.5 and I am confused. My question is this?

* When do I need to use pipe saddles or reinforments for branch connections?

* What is the max size pipe that a branch connection can be, given the main run pipe size?


I hear a lot of guys saying that a branch line has to be half as small as the main run. I can't find this claim anywhere.

Any light on this subject is appreciated.

US Iceman
08-01-2007, 05:12 PM
When do I need to use pipe saddles or reinforments for branch connections?


It's all about the calculations for allowable stress values I believe. An intersecting joint will require the removal of material, which makes this area of the pipe weaker. The reinforcement is added to increase the allowable stresses that can be applied to this area.

The same also applies to lateral connections too I believe.




What is the max size pipe that a branch connection can be, given the main run pipe size?


The typical method I remember is that the branch connection must be at least two pipe sizes smaller than the main header for a direct burn-in connection. However, this rule-of-thumb goes way back and I think only applies to joints without additional integral reinforcement.

I think most people now are using the weld-o-lets to provide the integral reinforcement for this purpose, but the same could be achieved with reinforcing pads.

That's about the extent of my knowledge with B31.5 codes. What it boils down to is, you have to do the calc's to verify the joint strength.

karelsdr
18-01-2007, 02:22 AM
A branch can be the same size if you are using a tee.To do a stab in the branch can only be too sizes down or smaller.Meaning you can`t stab a 3 inch into a 4 inch line. But you can do a 2 and a half.You need an engineer to calculate the strength or use a weld-a-let.Which is a pain because they take alot of welding.