ASME Codes for sizing a weld 3

Unclesam;
A compressed air system is nothing to fool around with because of the potential for harm. I would recommend you purchase a copy of ASME B31.1 Power Piping Code for your application. Section 104.3 of B31.1 "Intersections" will provide the information to engineer a 3" branch connection on the 10" main header. In addition, ASME B31.1 will provide guidance on approved material for fittings and post weld inspection requirements.

Please be aware that you should have a Welding Procedure Specification (WPS) and welder qualified to ASME Boiler and Pressure Vessel Code, Section IX if you are going to install the branch connection. If you hire a contractor, make sure that they have a National Board Certificate of Authorization to repair Boilers/Pressure Vessels. This way you have a contractor that knows what is required to perform this installation.

metengr,
Why do you advise ASME B31.1? Compressed air is not steam so why not use the appropriate standard i.e. ASME B31.1 - Process Piping.

DSB;
If you are referring to B31.3 Process Piping, B31.1 Power Piping includes water, steam, and gas piping systems. I am most familiar with B31.1 having spent a long time in Power Houses. Please read the Introduction, Section 100.1.2 and 122.8.3 of B31.1.

ASME/ANSI B 31.3 would be apt

B31.1, B31.3 and B31.9 could all be applicable; the selection should be by the owner, considering the type of facility it is (e.g. building services, power plant, process plant). Regarding weld size, make it full penetration with a cover fillet. Look to the applicable code for the required cover fillet size. Note that you also need to do an area replacement calc for this fabricated branch connection (or you could use a repad equal to twice the branch diameter with the thickness of the run pipe, which will always be conservative).

Unclesam,

In response to your original question,.....

With one exception, piping welds are not "sized" in the manner that structural welds are evaluated. Welds for piping are typically full penetration (develops full pipe strength of the section)or are generously sized fillet welds. The primary loading in most piping systems is pressure.

The exception is fabricated and pad reinforced "tees" at point of pipe intersection. These components are sized based on what is called the "area replacement technique". This technique uses the pressure loading on the joint to find the need for pad reinforcement.

I think that this answers you original question......


MJC

Weld'olets are full reinforced fittings <=3in. and because of the required fill of the weld (you can not miss it),
a 3" on a 10" sch 40, is fully reinforced specially for compressed air.
It is good to rely in the Codes too.
A must here: a weld procedure to assure the soundness of the weld.
ER