WELDING AN ADAPTER FITTING TO A PIPE

[imagineers]

So I have asked a similar question before however I am machining a part and welding it to a tube. 1.5" tube 1.65 wall. I am machining an adapter to house a pressure fitting and I was thinking of just making a slightly oversized hole and dropping the fitting in and welding around to join them. The thing is the part will be used on other assemblies with different tube sizes, so I figured this was the best way to weld this fitting as I can put the same size hole in any of the tubes, drop it in, and weld. The other option would be to cut a radius in the lower part of the fitting which would match the diameter of the tube its mating to, but the thing is that same fitting would not match the diameter of all the other tubes so I would need different diameter cuts for each tube to match if that makes sense. Is dropping the fitting in good practice and would I need to be concerned about anything like welds coming in contact with fluid or seeping down into the hole? its glycol and water going through and we have anticorrosives in place, just trying to see if there is any issues in doing this. Thanks

 

[imagineers]

 

[SnTMan]

imagineers, I am approaching from a pressure vessel codes standpoint, though it may not strictly apply in your case. Still, recognized good practices.

ASME Sec. VIII, Div. 1 permits either of your proposed details. There is really no functional difference between them. Your first alternative, which I'll call an insert detail, is probably the most practical.

Both details may be single fillet welded (i.e. around the OD only), which the B & PV Code permits for smaller fittings. If single fillet welded, both will have a crevice exposed to the process. This may or may not be acceptable to you.

A better weld detail would be to weld thru either the vessel wall or the fitting wall (full penetration groove weld) with perhaps also a fillet weld outside. Very common detail in the PV industry, but may not be needed for your application.

Regards,

Mike

On Edit: Might have added that whether or not you can tolerate protrusion inside the vessel inside surface will favor one detail over the other.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[imagineers]

Makes sense,I think dropping it into the run ad welding around is the easiest and provides a more universal application for the fitting in various tube sizes . Thanks

 

[gtaw]

What pressure is the system subject to? Not that it makes any difference if the system is require to comply with one of the ASME pressure piping codes. If I remember correctly, the fitting has to replace the volume of metal removed from the run pipe. A half coupling used as a branch fitting cannot be more than 1/4 the diameter of the run pipe, etc. Has anyone established whether the system is required to or should follow one of the pressure piping codes?

Best regards - Al