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Re: [MW:19854] Inconel 625 Cladded API 5L X65 - Purge and Pre-Heat

By Materials & Welding

Hi,

I think you should go for purging with dam technique.
Calculate the volume between the damps, the weld line will be in between the damps
(artificially created chamber). it is a general practice the one should displace the 6 times
volume of air keeping the purging flow rate at 20LPM.

After that, check the oxy content with analyzer & reduce the purging flow rate to
5 - 8LPM & the shielding gas flow rate will be 10 - 12LPM.

I hope it may help you.


Regards,

Zakir Ali.


From: Ken Waterhouse <waterhouse.ken@gmail.com>
Sent: Thu, 09 Jan 2014 18:54:37
To: materials-welding@googlegroups.com
Subject: [MW:19817] Inconel 625 Cladded API 5L X65 - Purge and Pre-Heat
Good Day Everybody,
 
I am working on a project for an Oil Major in Nigeria, and we are working with API 5L X-65 pipe, cladded with Inconel 625 (3-4mm THK).
 
The client specification requires a minimum pre-heat of 150 Deg C, as well as back purge Oxygen Content limitation of 500ppm for first 3 passes. The hardness limit is 250 HV10, and there is CVN testing at -29 Deg C, with minimum avg. 42J, minimum single 33J. Of course all other ASME IX standard mechanical testing is applicable too.
 
We are welding with ERNiCrMo-3 and ENiCrMo-3, so as to avoid microcracks and dilution into the clad material. The pipe is 6" OD and hence no backwelding or clad repair is possible from the inside.
 
The issue I am facing is acheiving a 500ppm MAX purge environment during welding. We have previously acheived this O2 requirement on our Duplex procedures, but these do not go anywhere near to the minimum temperature of 150 Deg C required with X-65. I have purchase heat resistant aluminium tape, and proper purge dam systems from InterCon. The issue is that at those elevated temperatures even the heat resistant tape does not adhere properly to the pipe surface, as well as leaving sticky residue all over the parts it comes in contact with. The tape is of high quality from a reputable brand. In order to acheive the O2 requirement we have been using a system whereby each welder has a helper that is removing the tape just ahead of the weld zone during welding, hence minimising the amount of purge lost through the root gap. This is not practical on such a hot pipe.
 
Does anyone have experience with the same or similar requirements? Any advice on practically acheiving both requirements, not only for procedure qualification, but also for production welding, where access is far more limited, and pipe spools are longer.
 
Thanks in advance,
 
Regards
Ken W

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