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Fillet Weld per Section VIII Div 1 UW-16(e)

Fillet Weld per Section VIII Div 1 UW-16(e)

Fillet Weld per Section VIII Div 1 UW-16(e)

(OP)
I am designing a pressure vessel and I want to weld a NPS 2.5 pipe to the outside surface of the pressure vessel for the inlet of fluids. The weld must be from the outside only and I'd strongly prefer not to make a groove or bevel on the opening.

UW-16(e) states: "Necks and tubes not exceeding NPS 6 (DIN 150) may be attached from one side only on either the outside or inside surface of the vessel.
(1) The depth of the welding groove or the throat of the fillet shall be at least equal to 1 1/4 tmin. The radial clearance between the vessel hole and the nozzle outside diameter at the unwelded side shall not exceed the tolerances given in Fig. UW-16.1 sketches (v-1),(v-2),(2-1), and (w-2). When welded from the outside only, the neck or tube shall extend to be at least flush to the inside surface of the vessel wall. Such attachments shall satisfy the rules for reinforcement of openings, except that no material in the nozzle neck shall be counted as reinforcement."

The pipe will be at least flush with the inside surface of the pressure vessel, as required by UW-16(e)(1).

From reading UW-16(e)(1), I think that it should be possible to use a fillet weld from the outside only, but figures (v-1) to (w-2) show the weld as from the inside only. UW-16(e)(2) states: "As an alternative to (1) above, when the neck or tube is attached from the outside only, a welding groove shall be cut into the surface to a depth of not less than tn on the longitudinal axis of the opening..."

Is it permissible to attach a NPS 2.5 pipe with a fillet weld only, as described in UW-16(e)(1)?

RE: Fillet Weld per Section VIII Div 1 UW-16(e)

jmec, I'd say it is permitted per UW-16(e)(1), provided it meets these requirements.

I'd also say it could be a poor practice, depending on the vessel service. Could you consider a detail per Fig UW-16.1(a)?

Regards,

Mike

RE: Fillet Weld per Section VIII Div 1 UW-16(e)

(OP)
Thanks Mike.

The vessel service is low pressure with non-lethal fluids. Fig UW-16.1(a) would be difficult with the manufacturing process we use, but we might have to consider it. I'm also considering using UW-16.1(f)(3)(a) and Fig UW-16.2 K. Is there a restriction on what can be considered a "Manufacturer's Standard" fitting for the purpose of UW-16.1(f)?  

RE: Fillet Weld per Section VIII Div 1 UW-16(e)

jmec, I doubt a piece of pipe would be so considered. Fig K is exactly equivalent to the detail you proposed earlier, i.e. Fig UW-16.1(v-1), welded outside. Trading one set of requirements for another.

"Low pressure" or not, non-lethal or not, crevices exposed to the process are normally to be avoided.

If your vessel is to be stamped, you can always consult with your AI.

Regards,

Mike

RE: Fillet Weld per Section VIII Div 1 UW-16(e)

We are welding UW-16(e)(2) nozzles into intermediate heads where both sides of the head are internal.

Outside and Inside is misleading.  I interpret that the the nozzle can point inside or outside of the vessel shell.  I think it is just saying you can't weld the internal joint of the Nozzle which would be near impossible anyway.

RE: Fillet Weld per Section VIII Div 1 UW-16(e)

We do "Set In" and "Set On" nozzles all the time, with no access to the second side.  It's called pipe branch connections.  All Sect VIII Div. 1 demands for 1.0 Joint Efficiency is that the weld be of equivalent quality as one welded from both sides.

Crevices may be a poor idea in some *services* but they are allowed by Sect I, III, VIII.  Look at any socket-welded fitting.  

jmec, look at the illustrations in VIII for Half-couplings and Integrally Reinforced couplings [O'Lets].  Neither requires you to set the fitting thru to the back side.   

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