Fillet Welds for pressure containment

[burnra]

There are lots of calculations for sizing of fillet welds. However I have not seen one for sizing of fillet welds for pressure containment. This may occur with the associated pipework for setting up hydrotesting etc. How can one be sure fillet weld size is accurate. Any references appreciated on this subject.

 

[BigInch]

Butt weld it, or use a weld-o-let. Why try to use a fillet weld at test pressures.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[unclesyd]

On our vaporized heating oil system (Therminol) we use both socket welds and weld-o-lets on large diameter pipe. we test all pipe to 175 psig using the heating fluid. The system operates a 70 psig @ 700°F so we have to use process fluid. Prior to any pressurization we do pull a vacuum to check for gross leaks. On all our jacketed pipe all the connections, inlet, vent and drain are use Weld-O-Lets. we test these spools with primary Therminol Condensate at 285°C @ 70 psig. I have never seen any problem with the welds. We do inspect fillet welds during fabrication

 

[BigInch]

Where are you using fillet the welds?

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[unclesyd]

I used the term Weld-O-Let where I should have used Sock-O-Lets. the original piping used set on nipples, and as we modified the piping spools we beefed up the connection. All the jackets use fillet welds on the Therminol, jacket side. The jacket is 5" or 6" is Sch 80 CS. The newer spools have the jacket beveled and a full out fillet weld with legs equal to wall thickness, a slight overkill

 

[BigInch]

Sounds more like a bevel weld (some kind of "interior" fillet weld), but I'll take your word for it.
I never use fillets on pressure containing parts, even on end plates for jacketed, and slip-ons are generally prohibited by most all of our clients anyway.

If it ain't broke, don't fix it. If it's not safe ... make it that way.