Welding of high thickness fittings on small thickness pipe

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crstn Associate Join Date: Aug 2009 Posts: 25 Good Answers: 1	Welding of high thickness fittings on small thickness pipe 11/19/2009 9:19 AM
	Hello to everyone. I am looking for a piece of advice in the following problem: Our corrosion dept is requestig to install new corrosion probes. The corrosion probes are installed through 2" nozzles that come from the manufacturer with a wall thickness 21mm. The nozzles are already bevelled. The wall thickness of existing pipe for some connection points is only 3mm for SAF2205 and 6mm for CS. Applicable code ASME B3.31 Contractor proposed to weld only few passes to have the weld thickness greater than the pipe wall and to let the remaining part of the bevel not filled with weld. Is this a common practice and in accordance with code requirements, or should be asked to reduce the external diameter of nozzle to have comparable thickness ~ 5-6mm with the run pipe wall ? ( tapering ) In case if is accepted, the PQR shall be qualified for 21 mm? or for actual thickness of weld? Thank you all for your time. Crstn
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	Pathfinder Tags: B3.31 Fittings Nozzle thickness Welding

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PennPiper Guru Join Date: Feb 2007 Location: Bayonet Point, Florida Posts: 635 Good Answers: 61	#1 Re: Welding of high thickness fittings on small thickness pipe 11/19/2009 10:25 AM
	You seem to have the wrong concept about making welds on pipe with two different wall thicknesses. The outside diameter of pipe is constant for a given size (6" NPS or DN 150). It is the inside diameter that reduces as the wall thickness increases. What is normally done is to Taper Bore the I.D. of the thicker wall item at a 1:3 slope. If you do this then you will have a weld that is standard for the thin wall pipe item. __________________ Do it once and do it right
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crstn Associate Join Date: Aug 2009 Posts: 25 Good Answers: 1	#2 In reply to #1 Re: Welding of high thickness fittings on small thickness pipe 11/19/2009 11:20 AM
	It's correct to taper bore the ID. Is giving more strength to the joint and looks better. However, in this way the position of probe inside the flow on the main run will be modified with ~ 8mm. I will check with manufacturer if is ok , or shall be taken other measures to preserve the probe position. Many thanks for your answer.
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#3 Re: Welding of high thickness fittings on small thickness pipe 11/19/2009 10:43 PM
	I am trying to visualize this. It seem as though the corrosion probe nozzle would be welded to the side of the main pipe, rather than being taper-fitted to the end. If this guess is right, it seems that you could taper the O.D. of the nozzle to get a wall thickness proportionate to that of the main pipe. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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crstn Associate Join Date: Aug 2009 Posts: 25 Good Answers: 1	#4 In reply to #3 Re: Welding of high thickness fittings on small thickness pipe 11/20/2009 10:55 AM
	Yes, the nozzles are to be welded on the side of the main pipes. This is the reason that initally I was thinking to taper the OD.
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crstn (2); PennPiper (1); Tornado (1)

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