3" + Process Pipe Socket welded 2

[InspCool]

Gentlemen,
Has there ever occurred the use of socket welded pipe over 2" for the use of process pipe (non-utility)? I have never seen it. The custom is that, as is stated in all piping specifications, the use of socket welded pipe is reserved for auxillary, small bore, clean, non-corrosive processes, 2" and under.

Has it been used in the industry? Is it good engineering practice? What are the limitations or justifications for its use or non-use above 2" for process pipe, specifically, Anhydrous Ammonia (non-refrigerated).

Thanks in advance,

InspCool

 

[pennpiper]

You asked:
Has it been used in the industry? Not to my knowledge.

Is it good engineering practice? To what (to use it or not use it)? There is a higher cost involved with large bore 3"(DN80)or larger Socket-weld construction than with common butt weld construction.

What are the limitations or justifications for its use or non-use above 2" for process pipe, specifically, Anhydrous Ammonia (non-refrigerated). Is it available in the larger sizes? By this I mean all the normally re4quired fittings and valves. You may have to transition to Flanged construction for Valves and Equipment connections anyway.

Is this a legitimate technical question or is this a school homework assignment?

Sometimes its possible to do all the right things and still get bad results

 

[moltenmetal]

Even if you wanted to do socket weld > 2", where would you find the fittings, and to what standard would they be manufactured?

 

[nickcaiyh]

Please refer to ASME B31.3 311.2.5

311.2.5 Socket Welds
(a) Socket welded joints (para. 328.5.2) should be
avoided in any service where crevice corrosion or severe
erosion may occur.
(b) Socket welded joints shall conform to the
following:
(1) Socket dimensions shall conform to ASME B16.5
for flanges and ASME B16.11 or MSS SP-119 for other
socket-welding components.
(2) Weld dimensions shall not be less than those
shown in Figs. 328.5.2B and 328.5.2C.
(c) Socket welds larger than DN 50 (NPS 2) shall not
be used under severe cyclic conditions.
(d) Adrain or bypass in a component may be attached
by socket welding, provided the socket dimensions conform
to Fig. 4 in ASME B16.5.

And socket fittings >2" would be hardly for procurment.

 

[Duwe6]

These huge Socket-Weld fittings are available. If, and only if, I cannot hire a competent open-root pipe welder do I allow them to be used. Per ASME, they are 'Legal' to use in about anything other than SectI inside-the-boiler stuff. But it is smarter, faster, and a little cheaper to just hire a competent open-root pipe welder.

 

[btrueblood]

Open root = butt weld connections?

 

[Duwe6]

"Open root = butt weld connections" Yes.

Degree-of-difficulty to make an open-root weld, such as butt-welding pipe, versus performing socketwelds [essentially just a wraparound fillet weld] is about an order of magnitude. But welders able to perform Code-compliant butt-welds on pipe are fairly easy to find, just not the cheapest ones to hire.