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Technical Discussions
A.Ramakrishna
NDT Inspector
ONGC, India, Joined Mar 2002, 1

A.Ramakrishna

NDT Inspector
ONGC,
India,
Joined Mar 2002
1
06:17 Mar-12-2002
How to measure minimum wall thickness of a seamless pipe

I have to monitor the wall thickness of drill pipes. I am using gamma ray for recording this. But I am afraid it shows average wall thickness across a cross section. But I am interested in knowing the minimum wall thickness and not average. How to do it?

I also suspect the wall thicknes measured includes the thickness of scales. How to get the thickness of sound pipe body excluding scales?


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

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
05:08 Mar-12-2002
Re: How to measure minimum wall thickness of a seamless pipe
: I have to monitor the wall thickness of drill pipes. I am using gamma ray for recording this. But I am afraid it shows average wall thickness across a cross section. But I am interested in knowing the minimum wall thickness and not average. How to do it?
.
: I also suspect the wall thicknes measured includes the thickness of scales. How to get the thickness of sound pipe body excluding scales?

Numerous models of hand-held ultrasonic thickness gages will easily measure the single wall thickness of steel pipes. Mineral scale is normally not included in the measurement because it has an acoustic impedance significantly different from that of steel. My company is among those that make equipment that should be suitable for your purposes.

--Tom Nelligan
Panametrics, Inc.
www.panametrics.com




    
 
 
Richard Kazares
Richard Kazares
05:24 Mar-12-2002
Re: How to measure minimum wall thickness of a seamless pipe
Depending on the quality and integrity of the data you seek you might consider various UT techniques starting from hand-held intrumentation but also including full C-Scan data using automated UT scanners.

Equipment existing that can provide measurement from the outside or inside of piping - as a function of location, geometry and other factors.

The advantage of C-Scan data is that you would have immediate access to enhanced analysis capabilities - including the ability to remove the scale thickness data from the overall thickness readings.

Further advantages of C-Scan data are full data retention for future comparisons (provides means of calculating corrosion rates) or other backup needs.


    
 
 
Greg
Greg
03:37 Mar-28-2002
Re: How to measure minimum wall thickness of a seamless pipe
There is no doubt that the most accurate method of determining minimum wall thickness would be by automated full length UT (this is what I do for a living!). However, if you already have a gamma system indicating through (average) wall thickness, a second PM detector/amp/decoder can be added and a backscatter (preffered for drill pipe diameters) system created. This will provide more localised thickness indication not averaged from opposit walls. Areas of concern can then be further investigated by manual UT gauge. I am assuming your gamma equipment is mounted in a rotating head.


    
 
 
Richard Kazares
Richard Kazares
04:57 Mar-28-2002
Re: How to measure minimum wall thickness of a seamless pipe
On-line, real-time UT measurements using either a moving scanner or solid state scanner with multiple transducers is also a possibility.

Depending on your operational environment (on-line, off-line, easy access etc.) varios solutions exist or could be adapted to provide the measurment results you seek.

In many cases the scale thickness (again depending on the geometry and actual conditions) can be removed from the readings.

We would be happy to discuss your application further by return e-mail.


: I have to monitor the wall thickness of drill pipes. I am using gamma ray for recording this. But I am afraid it shows average wall thickness across a cross section. But I am interested in knowing the minimum wall thickness and not average. How to do it?
.
: I also suspect the wall thicknes measured includes the thickness of scales. How to get the thickness of sound pipe body excluding scales?
.



    
 
 

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