Hi,
Find some Information which can help regarding selection of Butt and Socket.
When do you NOT want to use socket-welded fittings?
- in severely vibrational services as others have said
- in severely corrosive or high purity services, because all socket-welded fittings contain a deep crevice ideal for corrosion
- for high toxicity services where a radiographic inspection of each weld's integrity is required
- where the flexibility analysis tells you that they're no good because of the stress intensification issues indicated above (a rarety if the piping is otherwise designed and supported correctly)
- in services with expensive materials of construction (i.e. titanium etc.), because the extra material required in the SW versus BW fittings will often eat any savings in welding cost (combined with the corrosion issue above!)
- any time your welders are not familliar enough with them to realize that they must be fit with a shrinkage gap- it's the fittings which have been bottomed in the socket before welding that are most prone to failure
- beyond about 3" pipesize, regardless
When do you WANT to use socket-welded fittings? Virtually in all other circumstances where threaded connections have been ruled out. Socket-welded piping is quicker and easier to both fit AND weld and hence is far less expensive than the butt-welded alternative. Savings of 50%+ in installed cost can be expected in practice relative to butt welding.
Clearly your results may vary, but that's my take on the issue. Be careful about axiomatic statements, whether from me or others, that you might hear on this site! Case in point: unclesyd's "RTJ flanges are used on all heating fluid services". Although I bow at unclesyd's feet as he is an extremely knowledgeable engineer and I listen carefully to what he says, there are plenty of places where ordinary raised-face gasketed ANSI flanges are perfectly fine for use with heating fluids. Even 150# flanges, though I know there are people and companies which just say no to them for hot oil...
- in severely vibrational services as others have said
- in severely corrosive or high purity services, because all socket-welded fittings contain a deep crevice ideal for corrosion
- for high toxicity services where a radiographic inspection of each weld's integrity is required
- where the flexibility analysis tells you that they're no good because of the stress intensification issues indicated above (a rarety if the piping is otherwise designed and supported correctly)
- in services with expensive materials of construction (i.e. titanium etc.), because the extra material required in the SW versus BW fittings will often eat any savings in welding cost (combined with the corrosion issue above!)
- any time your welders are not familliar enough with them to realize that they must be fit with a shrinkage gap- it's the fittings which have been bottomed in the socket before welding that are most prone to failure
- beyond about 3" pipesize, regardless
When do you WANT to use socket-welded fittings? Virtually in all other circumstances where threaded connections have been ruled out. Socket-welded piping is quicker and easier to both fit AND weld and hence is far less expensive than the butt-welded alternative. Savings of 50%+ in installed cost can be expected in practice relative to butt welding.
Clearly your results may vary, but that's my take on the issue. Be careful about axiomatic statements, whether from me or others, that you might hear on this site! Case in point: unclesyd's "RTJ flanges are used on all heating fluid services". Although I bow at unclesyd's feet as he is an extremely knowledgeable engineer and I listen carefully to what he says, there are plenty of places where ordinary raised-face gasketed ANSI flanges are perfectly fine for use with heating fluids. Even 150# flanges, though I know there are people and companies which just say no to them for hot oil...
Regards,
SAHA
From: melyyan@gmail.com
To: materials-welding@googlegroups.com
Subject: [MW:6222] minimum butt weld joint
Date: Sat, 31 Jul 2010 19:05:10 +0400
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From: melyyan@gmail.com
To: materials-welding@googlegroups.com
Subject: [MW:6222] minimum butt weld joint
Date: Sat, 31 Jul 2010 19:05:10 +0400
Dear all;
I had a question regarding minimum butt weld joint?
Is there any code mentioning that NPS 2 & above shall be butt weld joints & less than 2" socket weld?
Please advice?
Regards
Majdi
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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