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Technical Discussions
Ahmed
Ahmed
13:31 Nov-05-2009
detection of 0.5mm pin-hole in 4" gas pipelines

Dear All

A client wants to detect a pin-hole 0.5 mm diameter in a stailess steel 4 " gas pipeline.

Of course he ideally needs a screening method but since LRGUT does not have this sensitivity, we wonder if there is an expert somewhere there to inform us about any new/conventional NDT method that can detect this small pin hole. Thank you and best regards.

    
 
 Reply 
 
Thomas Vogt
R & D, - -
Guided Ultrasonics Ltd, United Kingdom, Joined Apr 2007, 22

Thomas Vogt

R & D, - -
Guided Ultrasonics Ltd,
United Kingdom,
Joined Apr 2007
22
15:20 Nov-05-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to Ahmed at 13:31 Nov-05-2009 (Opening).

Dear Ahmed

maybe worth asking whether there is associated metal loss surrounding the pinhole (is it only in the centre of something bigger) in which case it may move it into the realms of GW capabilities?

Tom

    
 
 Reply 
 
AHMED
AHMED
08:16 Nov-06-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to Thomas Vogt at 15:20 Nov-05-2009 .

Dear Tom

Thank you for the reply.
The line is a stainless steel, ( no metal loss) and the pin are isolated pitting. The client wants to detect those before they become through wall defects and thus cause leak...
Gguided UT certainly would not be able to detect such small defects. Some mentioned E-PIT ( external Pipeline integrity Tool but I am not sure. Thankx.

Ahmed

    
 
 Reply 
 
S.V.Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 787

S.V.Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
787
15:13 Nov-06-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to Ahmed at 13:31 Nov-05-2009 (Opening).

Dear Ahmed,

A pin-hole by definition is through wall! If it has not progressed to that stage, it would be a pit. Since such pits usually develop at the surface (OD or ID) and since the pits that develop in the inside are the ones that may progress to the OD and become leaks, Eddy Current Test with differential ID coil could in theory detect such defects. In a pipeline, access would be the main constraint. So, basically you need to tackle two aspects: one is that of coil design, frequency selection etc. to ensure sensitivity and second access considerations.

Best regards

Swamy

    
 
 Reply 
 
Ahmed
Ahmed
15:59 Nov-06-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to S.V.Swamy at 15:13 Nov-06-2009 .

Thank you Mr. Swamy for the clarification and the proposition.

The line has access from outside ( not burried) and the client wants the test to be in service . 4 inc, diam, 3 mm thick, and a pit ( thank you not a pin hole!) of 0.5 mm dia. to be detected in a clean material ( no metal loss in the surronding of the pit) is to my experience a challenging problem. May be you with you nuclear NDT experience can convince me that a conventional tech can do the job ( ET?).

thanks and best regards.

    
 
 Reply 
 
Wieslaw Bicz
Engineering,
PBP Optel sp. z o.o., Poland, Joined Feb 2009, 252

Wieslaw Bicz

Engineering,
PBP Optel sp. z o.o.,
Poland,
Joined Feb 2009
252
13:45 Nov-07-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to Ahmed at 15:59 Nov-06-2009 .

It is not a problem to detect such small pinholes with suitable ultrasonic transducers. Even much smaller defects can be seen. The problem, that I see is as follow:
To check the pipe a suitable method must be developed. The simplest would be to use multi transducer head in a circular form, surrounding the pipe, that is moved along it. It is usable in production of pipes, but it is difficult for me to tell, if such solution can be used here.

    
 
 Reply 
 
S.V.Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 787

S.V.Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
787
12:15 Nov-08-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to Ahmed at 15:59 Nov-06-2009 .

Dear Mr. Ahmed,

Thanks for the clarification. Since access is not a problem, and since the pipe is not very thick, an encircling OD differential coil could be tried. Sensitivity is to be established by making blind holes of 0.3, 0.5 and 0.7 mm dia. by EDM to depth equal to diameter. This would help in calibration of the equipment too. I am sure you will be able to check out and determine yourself whether the method would be successful or not. There are formulas for selecting the optimal frequency but some trial and error will be needed and if you prefer, you can make your own coils too (we used to do that!). Best wishes.

    
 
 Reply 
 
David Hermantz
David Hermantz
18:52 Nov-15-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to S.V.Swamy at 12:15 Nov-08-2009 .

Hi,

This application came up in Edmonton a few years ago, an Eddy current array probe was chosen as the solution for a manual scanning method. It involved a lot of man-hours but provided the sensitivity required.

http://www.olympus-ims.com/en/probes/eca/subsurface/

Cheers,

David

    
 
 Reply 
 
Neil Burleigh
Sales
Krautkramer Australia Pty Ltd, Australia, Joined Dec 2002, 156

Neil Burleigh

Sales
Krautkramer Australia Pty Ltd,
Australia,
Joined Dec 2002
156
07:24 Nov-16-2009
Re: detection of 0.5mm pin-hole in 4" gas pipelines
In Reply to Ahmed at 15:59 Nov-06-2009 .

Dear Ahmed,
Just have come back from a promotional tour of the new Phasor CV/DM from GE very impressed. Reference block had 1 mm FBH from 12 to 1 mm below surface all easily resolved. A customer had a special piece of pipe with minute pits 0.2 - 0.5 mm dia being 30 - 70 % of wall thickness. It is a special test piece to certify UT thickness technicians. Inspection time was around 1/20th of normal UT thickness inspection time.
Contact local GE distributor but it is really new, so try johann.klein@ge.com. Johann was the technical support person from GE and he will point you in the right direction.
Regards
Neil Burleigh

    
 
 Reply 
 

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