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- since 1996 -
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Technical Discussions
Mr Burton
Mr Burton
03:50 Mar-17-2010
Pipe thickness and pitting

I would like to seek information about measuring wall thickness and pitting for a 350mm diameter, 20mm wall thickness, probably about 12mm now in places. Used for iron ore slurry.

 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
09:23 Mar-17-2010
Re: Pipe thickness and pitting
In Reply to Mr Burton at 03:50 Mar-17-2010 (Opening).

The first line of attack would be ultrasonic wall thickness measurement. To carry out wall thickness measurements with ultrasonics the pipe would have to be comfortably accessible and 'bare metal' i.e. free of coating, insulation, rust etc. Typically, measurements can be made - assuming we are talking of carbon steel - with an accuracy of 0,2 mm or so in the field. Oviously an asessment of the situation on site would be required.

If the line is insulated, an alternative method of measurement, without removing the insulation, might be Incotest. Incotest is a stand-off measurement system which can 'look' through insulation and assess the remaining wall thickness compared to one point where the insulation has been removed and a comparision is made.

You mention pitting. I wonder, considering the medium in the line (iron ore slurry), if there really is a problem with pitting. I tend to think that the problem would be erosion. However, if pitting is present and this is local loss of wall thickness rather than needle pitting, this should be possible to detect.

Needle pitting, which is usually a problem with exotic steel sorts, is very difficult to detect with either of the above methods (read impossible). Radiography may work.

 
 Reply 
 
Aaron Greenbank
Sales
Innospection, United Kingdom, Joined Jan 2010, 1

Aaron Greenbank

Sales
Innospection,
United Kingdom,
Joined Jan 2010
1
10:33 Mar-17-2010
Re: Pipe thickness and pitting
In Reply to Mr Burton at 03:50 Mar-17-2010 (Opening).

Dear Sir,

Another method that you may wish to consider is SLOFEC, this is an eddy current based technique which uses magnetic saturation to aid the induction of eddy currents into the specimen. This is an excellen tmethod for fast screening for corrosion typical of what you have described.

 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
13:59 Mar-17-2010
Re: Pipe thickness and pitting
In Reply to Mr Burton at 03:50 Mar-17-2010 (Opening).

We have a general application note on ultrasonic corrosion gaging that may be of interest if you're new to the subject:

http://www.olympus-ims.com/en/ndt-application/183-id.209715222.html

 
 Reply 
 
Rich Roberts
Engineering, Executive Managment
Quest Integrity Group, USA, Joined Nov 1998, 78

Rich Roberts

Engineering, Executive Managment
Quest Integrity Group,
USA,
Joined Nov 1998
78
14:11 Mar-17-2010
Re: Pipe thickness and pitting
In Reply to Mr Burton at 03:50 Mar-17-2010 (Opening).

You may want to consider applying an Ultrasonic (UT) based Intellingent Pig technology. Even if the line is not designed to be inspected by way of intelligent pigs, there are pigs which are capable of running in these lines. Some Ultrasonic based intelligent pigs will provide +100% overlapping coverage to ensure the entire surface is inspected. Detecting and quantifying Corrosion, Pitting, Erosion along with any deformation (i.e. Denting, Ovality, Bulging, etc.) can be accomplished with one pass of the intelligent pig tool.

 
 Reply 
 
Jim Kovarik
Engineering
Lixi, Inc., USA, Joined Nov 1998, 39

Jim Kovarik

Engineering
Lixi, Inc.,
USA,
Joined Nov 1998
39
17:08 Mar-18-2010
Re: Pipe thickness and pitting
In Reply to Mr Burton at 03:50 Mar-17-2010 (Opening).

You may also want to consider the Lixi Profiler if the line will be or can be evacuated.

 
 Reply 
 
Zach McCann
Zach McCann
08:50 Mar-31-2010
Re: Pipe thickness and pitting
In Reply to Mr Burton at 03:50 Mar-17-2010 (Opening).

Hello Mr Burton following on from the information Aaron sent you I represent Innospection here in Australia. I would be happy to discuss this if you woudl care to drop me an e-mail.

 
 Reply 
 

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