Welding pipe to pressure vessel nozzle 1

[ET50]

If you have a code certified pressure vessel, with a stub pipe coming off the side and bottom head of the vessel, are you allowed to weld a pipe directly to it?

Is this acceptable, or do all connections need to be flanged or screwed into a threaded connection on pressure vessels.

The vessel is approx 18 inches OD x 4 ft T-T

 

[metengr]

If you have a code certified pressure vessel, with a stub pipe coming off the side and bottom head of the vessel, are you allowed to weld a pipe directly to it?

Weld the pipe directly to what? To the pipe stub, like a butt weld? To the shell, for a new nozzle? To the bottom head for a new nozzle?

What is the purpose for welding the pipe to this vessel?

What is the function of the pressure vessel? Pressure?

Are you qualified to perform this work by virtue of having a National Board Certificate of Authorization to Repair Boiler/Pressure Vessels?

 

[ColonelSanders83]

Eexactly what code is this vessel compiant with? What country you are in might be usefull too.

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

 

[ET50]

Welding a 2 inch sch 40 pipe to a 2 inch sch 40 pipe stub (a butt weld) is what we are concidering. We are wondering if this is acceptable? If it's acceptable, does it need to certified as a repair?

If it needs to be certified as a repair to the vessel we will go with a flanged connection. The tank (vessel) contains 245 fa refrigerant, and we are trying to make it leak free. Threaded connections have leaked on us in the past and thats unacceptable. If we can't weld we'll explore different gasket materials for flanged connections.

 

[ET50]

We are in the US and it's a Section VII, Div 1 code stamped vessel

 

[metengr]

ET50;
For 2" Sch 40 pipe nozzle, it would make better sense to weld versus using a threaded connection. If you are going to butt weld or fillet weld a flange to the existing nozzle on this vessel, you need an R-Certificate issued by the National Board. If you don't have this, hire a repair contractor that is licensed for boiler/pressure vessel weld repair and sub this work to them.

 

[MrBTU]

The ASME Code U stamp ends at your butt weld prep. The ASME Code has nothing to do with your welding on of a pipe to the stub end (see U-1(e)(1)(a) and UW-13(h). You may have other piping specs ASME 13.1 or 13.3 that apply, but ASME Code Sect VIII Div 1 does not. So to answer your question - yes, by the Code you are allowed to do this, and no, all connections do not need to be flanged or threaded.

 

[ET50]

Mr BTU,

Thanks for the clarification. That's exactly what I needed to hear.

 

[jte]

To back up what MrBTU stated, see Interpretation VIII-1-89-115:

Question: Two vessels were fabricated by a manufacturer in accordance with the requirements of Section VIII, Division 1 and were stamped accordingly. Nozzles with weld end connections were provided on the vessels. Are the field welds for the connections to these nozzles considered within the Scope of Section VIII, Division 1?

Reply: No, see U-1(e)(1)(a).

The weld metal and pipe are in the scope of the piping code which you are working to. Yes, it is understood that part of the nozzle (vessel) will be melted and refrozen in the welding process.

jt