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Chuck Davis
,
Mexico, Joined May 2016, 12

Chuck Davis

,
Mexico,
Joined May 2016
12
06:33 May-12-2016
AUT for mainline pipe inspection

I need some advice please. Our client is proposing mainline production for his automatic welding company to produce from 100 to 120 welds per day. This is for one spread. It is relatively flat land.

Is that really possible? 6 days a week? And if so, would there be a sound reason to have a second AUT complete unit for back up?

Would 100 to 120 welds require a 4 man crew for AUT?

If there is production of 100 to 120 welds per day, is AUT faster than crawlers?

Thanks for the help.

 
 Reply 
 
Rosario Molica Nardo
Engineering, NDT Engineer
AdES NDT Ltd, United Kingdom, Joined Apr 2014, 6

Rosario Molica Nardo

Engineering, NDT Engineer
AdES NDT Ltd,
United Kingdom,
Joined Apr 2014
6
11:05 May-12-2016
Re: AUT for mainline pipe inspection
In Reply to Chuck Davis at 06:33 May-12-2016 (Opening).

Chuck,
It depends on the diameter and the wall thickness of the pipeline. You have to consider the time for the band/scanner positioning. Then the scanning time and the interpretation time. For most of the commonly used AUT systems, the scanning speed is in the range 30 to 80 mm/sec. Based on that, you can try to calculate the scanning time for your scope of work. On top of that, you have to consider the time for the calibrations (depending on the specification/procedure, it can be every weld or every 5 welds or every 10 welds, etc.). Interpretation time is a "random" variable. A clean strip chart requires relatively "no time" to be assessed. "Dirty" welds will require much more time.
The crew depends again on the diameter of the pipeline. If it is a large OD pipe for that type of production rate, I would say that you need at least 2 AUT operator (or 1 operator and 1 supervisor) and probably 3x scanner technicians (2 working on the "scanned" weld and the third one that can clean the following weld/cooling it if needed/setup the band/etc). 100 welds on a 10 hours shift means one weld every 6 min. It looks to me a really challenging target for one spread (for both welding and AUT). However, AUT would be faster than RT done with crawlers.
A complete backup for the AUT system on site I would say that is "mandatory".

Regards
Rosario

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1286

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1286
14:43 May-12-2016
Re: AUT for mainline pipe inspection
In Reply to Chuck Davis at 06:33 May-12-2016 (Opening).

Chuck, there are many videos on YouTube illustrating automated welding and AUT (e.g. https://www.youtube.com/watch?v=q4wh0KCKL48). Indeed the process can be very efficient. In the 1990s in TCPL, we were making up to 140 welds per day with a crew welding 48 inch diameter pipe. The whole process is designed to separate the activities into roughly equal timed stages. Typically welds are made with 2 welding bugs in each welding "shack". Each bug is configured to make a single pass and each pass requires about 4-6 minutes from the time the shack is lowered to the time it is removed and moved to the next joint. AUT follows the welding shacks and must keep up with the 4-6 minute cycle time in order to provide its function as a process control.
There are extra costs and time required in AUT. You must obtain samples of the TMCP pipe material to determine velocities to properly configure your delay laws. You must also design and build calibration blocks specific for each project and material.
Operators are much more common now than they were 25 years ago, but many are not as good as they think they are or claim to be. Too many do not bother to follow the specific details in a qualified procedure and would rather just use their own judgement. This is a very critical aspect because an audit of the work could end up identifying deviations from the procedure that will result in sections of the pipeline being dug up for repair. This will cost the company a lot of money and its reputation (much like the X-ray film scandal of the Alyeska Pipeline in 1975).
You noted that your pending project is only a single Spread. However, it is more important to learn how the spread will be handled. We often had a single spread being done with a Mainline crew and a Poorboy crew (both using automated welding) and there there were also tie-in crews for manual welding. The Mainline and Poorboy would of course require a separate AUT crew for each. Tie-in crews using manual welding could be done using X-ray, but some companies have provided small AUT scanners qualified for manual weld evaluation.

Finally, you asked about spares. I suspect you would never send out a single X-ray crawler to a remote site because it could break down and take days to fix. The same applies to AUT apparatus. Perhaps not all parts need spares, but some of the more critical ones should definitely be identified and spares ensured for the project.

 
 Reply 
 
James Scalf
NDT Inspector,
Global Integrity, Canada, Joined Oct 2012, 274

James Scalf

NDT Inspector,
Global Integrity,
Canada,
Joined Oct 2012
274
22:15 May-17-2016
Re: AUT for mainline pipe inspection
In Reply to Ed Ginzel at 14:43 May-12-2016 .

Mr. Ginzel,

I was curious when you said in your reply that you were setting up the AUT process 4-6 minutes after the Automated welding was complete were you not concerned that the examination of the weld material might have been for not? Multi-pass welds can take hours (sometimes days), even with controlled cooling rates, to stress relieve and until it has completed its cycle, thermal loading and then cooling, it can crack at anytime.
I had this happen in a laydown yard once and it was only due to the fact that my helper happened to be leaning on a section we had just inspected and heard a strange ping sound that we even knew the weld had cracked which was what caused the ping sound.
Again I am not questioning the job you did, as a matter of fact I find your expertise and posts generally excellent and good reads, but was wondering if post weld stress relief was ever a concern on the job. Cheers...

 
 Reply 
 
Steven Doc
Other, Quality Manager
Siemens Energy, Egypt, Joined Feb 2011, 187

Steven Doc

Other, Quality Manager
Siemens Energy,
Egypt,
Joined Feb 2011
187
23:24 May-17-2016
Re: AUT for mainline pipe inspection
In Reply to James Scalf at 22:15 May-17-2016 .

James,
Stress relieving on mainline pipe? Thus is pipeline being discussed, not piping. When material of piping is susceptible to cracking, specifications shall call for delayed NDT. Pipeline it is quite normal for AUT to be all over the completed weld as soon as practically possible after weld completion.

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1286

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1286
01:00 May-18-2016
Re: AUT for mainline pipe inspection
In Reply to Steven Doc at 23:24 May-17-2016 .

Indeed, Steven is correct. Concerns for hydrogen cracking are addressed by proper selection of consumables and a qualified welding procedure. The only "delay" is the surface temperature of the pipe. On land-lay projects there may be 4-6 completed welds between the "cap shack" and the AUT in summer, and 2-3 welds in winter. On off-shore barge work there is in fact a separate step of water dousing of the weld just prior to AUT to get the surface temperature to just below 100°C .

 
 Reply 
 
Chuck Davis
,
Mexico, Joined May 2016, 12

Chuck Davis

,
Mexico,
Joined May 2016
12
18:55 Jun-27-2016
Re: AUT for mainline pipe inspection
In Reply to Ed Ginzel at 14:43 May-12-2016 .

You know your stuff Ed. If I had the money to get you to México, I would.

Do you know the answer to a crawler question? Is there any advantage over isotope controls vs. magnetic controls. If you ever get down to Guadalajara, you have your house here.

 
 Reply 
 

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