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08:42 Feb-21-2008
Nor Azman Zakaria
Crack detection on CS Piping

We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?


 
00:04 Feb-21-2008

Florin Turcu

R & D
Dept. of Electrical Systems and Automation - University of Pisa,
Italy,
Joined Jul 2007
9
Re: Crack detection on CS Piping Can you please indicate the type of the coating?
Thank You

----------- Start Original Message -----------
: We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
------------ End Original Message ------------




 
03:42 Feb-21-2008

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
------------ End Original Message ------------

Widespread SCC in carbon steel piping is not usual unless there is a specific damage mechanism such as caustic or amine cracking. You first need to clarify the root cause of the cracking and therefore the mechanism that stimulates it.

You might be able to screen for areas of activity with Acoustic Emission which will require some insulation removal but not all. You may also need to cycle pressure in the pipe to increase cracking acativity or monitor for a period of time during normal process if the mechanism is purely environment driven The approach ahs been very successful for SCC on Stinless Piping.

I assume you have alreday investigated some of the cracking and you know orientation, typical size and whether these occur in cluster populations. If the are large cracks or occur in dense clusters Long Range UT may give indications but you would probably have to trial the approach.

Depending on diamter, wall thickness and access plus cost benefit you may be able to inspect from the inside with a smart pig or similar configured tool.

You probbaly need to do a risk assessment on how these flaws affect perfoerewnce and integrity of the system and what you plan to do when you find them. If the presence poses such a risk you need to remove the pipe it may be cost effective to just have a pipe replacement plan rather than spending a lot on sophisticated inspection.

If you do not have access to NDE specialist support define the problem and take it to a number of the bigger NDE vendors on the Forum who can propose solutions and effectiveness.



 
02:34 Feb-22-2008
Claudio Allevato
Re: Crack detection on CS Piping -Mr. Zakaria,

Acoustic emission testing has been successfully used to detect environmentally driven damage mechanisms, such as SCC in carbon and SS piping systems.

The AET probes make contact with the surface of the piping (every approx. 20 feet) using ¼” solid SS waveguides, perforating the insulation. No insulation removal is necessary.

The most important element on this methodology is the stressing procedure. The success of the AET inspection depends heavily on choosing the appropriate stressing method. If the cracks are predominantly in the longitudinal direction, then a pressurization test, while the piping is in service will be very effective at detecting and locating active cracking. On the other hand, if the cracks are predominantly in the circumferential direction, then pressurizing the pipe may not produce good results because the Hoop direction is “parallel” with the direction of the cracks. In this later case, a temperature gradient might produce better results, assuming the pipe is hot enough.

In case the cracks are randomly oriented ( most likely case for SCC) the in-service pressurization might still reveal the most significant cracks, as long as the pressurization is able to take the piping system up to approximately 120% of the maximum operating pressure over the last 12 months, and still be safely below the PSV set points.

Please feel free to contact me directly, should you desire to discuss this further.

Thank you.

Claudio Allevato

Principal - Corp. AET Level III - ASNT Cert. 73985

Stress Engineering Services, Inc.

13800 Westfair East Drive, Houston, TX - 77041 - USA

Office : (281) 955 2900

Mobile: (281) 682 4682

ca@stress.com




 
00:50 Feb-25-2008

Thomas Vogt

R & D, - -
Guided Ultrasonics Ltd,
United Kingdom,
Joined Apr 2007
22
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: : We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
: Widespread SCC in carbon steel piping is not usual unless there is a specific damage mechanism such as caustic or amine cracking. You first need to clarify the root cause of the cracking and therefore the mechanism that stimulates it.
: You might be able to screen for areas of activity with Acoustic Emission which will require some insulation removal but not all. You may also need to cycle pressure in the pipe to increase cracking acativity or monitor for a period of time during normal process if the mechanism is purely environment driven The approach ahs been very successful for SCC on Stinless Piping.
: I assume you have alreday investigated some of the cracking and you know orientation, typical size and whether these occur in cluster populations. If the are large cracks or occur in dense clusters Long Range UT may give indications but you would probably have to trial the approach.
: Depending on diamter, wall thickness and access plus cost benefit you may be able to inspect from the inside with a smart pig or similar configured tool.
: You probbaly need to do a risk assessment on how these flaws affect perfoerewnce and integrity of the system and what you plan to do when you find them. If the presence poses such a risk you need to remove the pipe it may be cost effective to just have a pipe replacement plan rather than spending a lot on sophisticated inspection.
: If you do not have access to NDE specialist support define the problem and take it to a number of the bigger NDE vendors on the Forum who can propose solutions and effectiveness.
------------ End Original Message ------------

Hi

I agree guided wave UT could be an effective solution, especially considering that it is insulated (what is it insultated with? mineral wool?).

But I also agree it should be tried out first on known samples with different severity of SCC. If the SCC is oriented randomly you have crack components in the circumferential direction, which are easier to detect than if they are oriented in the longitudinal direction. Also, as mentioned, it should be easier to detect the denser the network is. We have found SCC using guided waves on stainless steel heat exchanger tubes and creep cracking in reformer tubes. However, I don't know of any studies relating the reflection amplitude to the severity of the SCC.

A problem therefore is the sizing of any indications, not to mention the setting of an appropriate call level.

Another possible indirect way of detecting SCC would be a change in the signal attenuation.

For screening purposes all this may be good enough. Even if you cannot size properly, it could tell you which sections of pipe to concentrate on first.

If you do try it operator experience is crucial.

Regards,
Thomas


 
05:43 Feb-25-2008

Sang Kim

Consultant, NDT Trainer
Guided Wave Analysis LLC,
USA,
Joined Feb 2008
44
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: : : We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
------------ End Original Message ------------
Hello,

I suggest high-frequency ultrasonic guide wave inspection/monitoring for finding accumulated SCC cracks because the pipeline is insulated. Depending on the wall thickness of pipe, you can operate the high-frequency torsional guided wave up to 250 kHz with magnetostrictive sensor (MsS) system. The torsional guided wave generated with MsS Probe has high signal-to-noise ratio by reducing the generation of flexural wave mode with 360-degree covering probe along the circumference of pipe. Once the MsS Probe is epoxy-bonded to a location of the pipe, the pipeline can be inspected and monitored periodically without reinstallation. The ultrasonic guided wave monitoring has the following processes: the guided wave probe is permanently installed on the pipe; baseline data are obtained, any defect indications or geometric features are verified with baseline data (the same to guided wave inspection); the pipe is periodically tested and the periodic data are compared with the baseline data to identify structural changes with time. With the guided wave monitoring, we can find smaller defect (0.5 % cross-sectional area with painted insulated pipe having good surface condition) in the pipe and even tell defect generation or growth in the geometric features because of the reference signal. The MsS Probes have been installed for guided wave inspection/monitoring in pipelines around the world because it is much cost effective in securing the safety of piping structure for a long period. Because the guided wave has high repeatability, the probe is also used for crack growth of rivet hole in airplane structure. If you want to try this or discuss it, please contact me at skim@gwanalysis.com.

Thanks,

Sang Kim




 
08:06 Feb-26-2008
azman
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: : : : We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
: Hello,
: I suggest high-frequency ultrasonic guide wave inspection/monitoring for finding accumulated SCC cracks because the pipeline is insulated. Depending on the wall thickness of pipe, you can operate the high-frequency torsional guided wave up to 250 kHz with magnetostrictive sensor (MsS) system. The torsional guided wave generated with MsS Probe has high signal-to-noise ratio by reducing the generation of flexural wave mode with 360-degree covering probe along the circumference of pipe. Once the MsS Probe is epoxy-bonded to a location of the pipe, the pipeline can be inspected and monitored periodically without reinstallation. The ultrasonic guided wave monitoring has the following processes: the guided wave probe is permanently installed on the pipe; baseline data are obtained, any defect indications or geometric features are verified with baseline data (the same to guided wave inspection); the pipe is periodically tested and the periodic data are compared with the baseline data to identify structural changes with time. With the guided wave monitoring, we can find smaller defect (0.5 % cross-sectional area with painted insulated pipe having good surface condition) in the pipe and even tell defect generation or growth in the geometric features because of the reference signal. The MsS Probes have been installed for guided wave inspection/monitoring in pipelines around the world because it is much cost effective in securing the safety of piping structure for a long period. Because the guided wave has high repeatability, the probe is also used for crack growth of rivet hole in airplane structure. If you want to try this or discuss it, please contact me at skim@gwanalysis.com.
: Thanks,
: Sang Kim
------------ End Original Message ------------

Hi Sang Kim & Thomas

Thanks for your response. Sorry for not describing the problem in detail. The cracks were primarily SCC oriented diagonally (45 deg off longitudinal) and located midway between weldments and pipe supports. We do have another crack which originates near weldment and going circumferentially.

We have sent these crack samples for metallurgical and more or less concluded that it is Caustic SCC. The caustic is suspected to be contributed by rockwool insulation binder and rain water through the cladding.

Your suggestion on high freq guided wave is worth trying. How is this different from long range UT? We know that LRUT has been partly sucessful with general corrosion under insulation but not with crack-like defects.
The baseline method seems logical but in order to do that we need to establish the baseline readings. That means verifying the wave against visual inspection, which in any case we hv to strip open the pipe.

Anyhow, I would appreciate if you can explain more on the High Freq Guided Wave.


 
08:25 Feb-26-2008
azman
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: -Mr. Zakaria,
:
: Acoustic emission testing has been successfully used to detect environmentally driven damage mechanisms, such as SCC in carbon and SS piping systems.
:
: The AET probes make contact with the surface of the piping (every approx. 20 feet) using ¼” solid SS waveguides, perforating the insulation. No insulation removal is necessary.
:
: The most important element on this methodology is the stressing procedure. The success of the AET inspection depends heavily on choosing the appropriate stressing method. If the cracks are predominantly in the longitudinal direction, then a pressurization test, while the piping is in service will be very effective at detecting and locating active cracking. On the other hand, if the cracks are predominantly in the circumferential direction, then pressurizing the pipe may not produce good results because the Hoop direction is “parallel” with the direction of the cracks. In this later case, a temperature gradient might produce better results, assuming the pipe is hot enough.
:
: In case the cracks are randomly oriented ( most likely case for SCC) the in-service pressurization might still reveal the most significant cracks, as long as the pressurization is able to take the piping system up to approximately 120% of the maximum operating pressure over the last 12 months, and still be safely below the PSV set points.
:
: Please feel free to contact me directly, should you desire to discuss this further.
:
: Thank you.
:
: Claudio Allevato
: Principal - Corp. AET Level III - ASNT Cert. 73985
: Stress Engineering Services, Inc.
: 13800 Westfair East Drive, Houston, TX - 77041 - USA
:
: Office : (281) 955 2900
: Mobile: (281) 682 4682
: ca@stress.com
------------ End Original Message ------------

Mr Allevato

We have done AET previously, but for a leaking vessel. In that case, we have already identified the crack, AET was just used to sizeit before we can shutdown and make permanent repair.

My objective now is to determine whether there are any more cracks on our insulated pipings. If I understand correctly, AET normally requires baseline measurement intepretation of cracks depend on the comparison between actual reading and baseline.


 
01:22 Feb-26-2008
Mikhail Sokolov
Re: Crack detection on CS Piping Hello!
I can offer our crack detection tool based on EMAT angle beam solution. This tool was tested last summer on Gasprom plants. Please visit http://www.diakont.ru/wins/control1/ema.shtml (all information in russian) or contact me via e-mail.

----------- Start Original Message -----------
: We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
------------ End Original Message ------------




 
08:49 Feb-26-2008

Thomas Vogt

R & D, - -
Guided Ultrasonics Ltd,
United Kingdom,
Joined Apr 2007
22
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: : : : : We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
: : Hello,
: : I suggest high-frequency ultrasonic guide wave inspection/monitoring for finding accumulated SCC cracks because the pipeline is insulated. Depending on the wall thickness of pipe, you can operate the high-frequency torsional guided wave up to 250 kHz with magnetostrictive sensor (MsS) system. The torsional guided wave generated with MsS Probe has high signal-to-noise ratio by reducing the generation of flexural wave mode with 360-degree covering probe along the circumference of pipe. Once the MsS Probe is epoxy-bonded to a location of the pipe, the pipeline can be inspected and monitored periodically without reinstallation. The ultrasonic guided wave monitoring has the following processes: the guided wave probe is permanently installed on the pipe; baseline data are obtained, any defect indications or geometric features are verified with baseline data (the same to guided wave inspection); the pipe is periodically tested and the periodic data are compared with the baseline data to identify structural changes with time. With the guided wave monitoring, we can find smaller defect (0.5 % cross-sectional area with painted insulated pipe having good surface condition) in the pipe and even tell defect generation or growth in the geometric features because of the reference signal. The MsS Probes have been installed for guided wave inspection/monitoring in pipelines around the world because it is much cost effective in securing the safety of piping structure for a long period. Because the guided wave has high repeatability, the probe is also used for crack growth of rivet hole in airplane structure. If you want to try this or discuss it, please contact me at skim@gwanalysis.com.
: : Thanks,
: : Sang Kim
:Hi Sang Kim & Thomas
: Thanks for your response. Sorry for not describing the problem in detail. The cracks were primarily SCC oriented diagonally (45 deg off longitudinal) and located midway between weldments and pipe supports. We do have another crack which originates near weldment and going circumferentially.
: We have sent these crack samples for metallurgical and more or less concluded that it is Caustic SCC. The caustic is suspected to be contributed by rockwool insulation binder and rain water through the cladding.
: Your suggestion on high freq guided wave is worth trying. How is this different from long range UT? We know that LRUT has been partly sucessful with general corrosion under insulation but not with crack-like defects.
: The baseline method seems logical but in order to do that we need to establish the baseline readings. That means verifying the wave against visual inspection, which in any case we hv to strip open the pipe.
: Anyhow, I would appreciate if you can explain more on the High Freq Guided Wave.
------------ End Original Message ------------

Hi,

I am not aware of any studies or publications that say "high frequency GW" will give you best results on SCC for any pipe under any conditions for any inspection range (i.e. no limitations!), but am interested to see them.

There are many factors, which need clarifying before making a statement. Contact me if you want more information, else I can put you into touch with a GW service provider in your region.

Thomas


 
00:42 Feb-27-2008

Sang Kim

Consultant, NDT Trainer
Guided Wave Analysis LLC,
USA,
Joined Feb 2008
44
Re: Crack detection on CS Piping ----------- Start Original Message -----------
: : : : : : We are facing multiple cracks (SCC) on carbon steel piping throughout the plant. As all of them are insulated, do you know of any method that can quickly scan the pipes instead of stripping all of the insulation and doing visual?
: : : Hello,
: : : I suggest high-frequency ultrasonic guide wave inspection/monitoring for finding accumulated SCC cracks because the pipeline is insulated. Depending on the wall thickness of pipe, you can operate the high-frequency torsional guided wave up to 250 kHz with magnetostrictive sensor (MsS) system. The torsional guided wave generated with MsS Probe has high signal-to-noise ratio by reducing the generation of flexural wave mode with 360-degree covering probe along the circumference of pipe. Once the MsS Probe is epoxy-bonded to a location of the pipe, the pipeline can be inspected and monitored periodically without reinstallation. The ultrasonic guided wave monitoring has the following processes: the guided wave probe is permanently installed on the pipe; baseline data are obtained, any defect indications or geometric features are verified with baseline data (the same to guided wave inspection); the pipe is periodically tested and the periodic data are compared with the baseline data to identify structural changes with time. With the guided wave monitoring, we can find smaller defect (0.5 % cross-sectional area with painted insulated pipe having good surface condition) in the pipe and even tell defect generation or growth in the geometric features because of the reference signal. The MsS Probes have been installed for guided wave inspection/monitoring in pipelines around the world because it is much cost effective in securing the safety of piping structure for a long period. Because the guided wave has high repeatability, the probe is also used for crack growth of rivet hole in airplane structure. If you want to try this or discuss it, please contact me at skim@gwanalysis.com.
: : : Thanks,
: : : Sang Kim
: : Hi Sang Kim & Thomas
: : Thanks for your response. Sorry for not describing the problem in detail. The cracks were primarily SCC oriented diagonally (45 deg off longitudinal) and located midway between weldments and pipe supports. We do have another crack which originates near weldment and going circumferentially.
: : We have sent these crack samples for metallurgical and more or less concluded that it is Caustic SCC. The caustic is suspected to be contributed by rockwool insulation binder and rain water through the cladding.
: : Your suggestion on high freq guided wave is worth trying. How is this different from long range UT? We know that LRUT has been partly sucessful with general corrosion under insulation but not with crack-like defects.
: : The baseline method seems logical but in order to do that we need to establish the baseline readings. That means verifying the wave against visual inspection, which in any case we hv to strip open the pipe.
: : Anyhow, I would appreciate if you can explain more on the High Freq Guided Wave.
: Hi,
: I am not aware of any studies or publications that say "high frequency GW" will give you best results on SCC for any pipe under any conditions for any inspection range (i.e. no limitations!), but am interested to see them.
: There are many factors, which need clarifying before making a statement. Contact me if you want more information, else I can put you into touch with a GW service provider in your region.
: Thomas
------------ End Original Message ------------
Hello! Azman and Thomas,

I mentioned ¡°high-frequency¡± guided wave. I wanted to differentiate the guided wave with frequency. I usually use the word ¡°high-frequency¡± guided wave if the operating frequency of guided-wave inspection and monitoring is higher than 100 kHz. More than 90 percent of guided-wave inspection uses less than 70 kHz for long-range inspection. Since the MsS guided-wave system was designed to operate from 4 kHz to 250 kHz, MsS system generateswell high-frequency torsional guided wave in pipe. Also magnetostrictive sensor (MsS) probe continuously covers 360-degree around the circumference so that reduces the generation of flexural wave mode that is usually generated with discretely arrayed transducers. Due to higher modes of flexural mode, the discretely arrayed transducers cannot generate well high-frequency torsional mode without generating flexural wave mode if the attached transducers do not cover continuously the circumference of pipe (torsional mode is axial symmetric mode, but flexural mode is not axial symmetric).

I suggested using ¡°high-frequency¡± guided wave because I thought that the SCC defects are mostly small. In guided wave, the higher the operating frequency, the more sensitive the inspection or monitoring is to small defects. Because of generation of the 2nd-order torsional mode, the operating frequency can be increased up to the cut-off frequency of the 2nd-order torsional mode (about 128 kHz for 0.5-inch-thick wall, 250 kHz for 0.25-inch-thick wall). Since the SCC is located midway between weldments and pipe supports in this case, using the ¡°high-frequency¡± guided wave is much better choice. Usually a support generates extraneous signals (mostly flexural mode) at lower frequency operation (If anyone has much experience in field test, he will agree on this). The generation of extraneous signals reduces the signal-to-noise ratio of signals following the supports or weldments.

Thanks,
Sang Kim




 


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