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Technical Discussions
Jairo Humberto Guzman
Jairo Humberto Guzman
04:29 Dec-30-1998
tofd applications for hot hydrogen attack on carbon steel

We have measurement hydrogen damage on carbon steel presure vessels, using 3 ultrasonics methods:

1- velocity ratio compared with a sample without H2 damage.
2- Ultrasonic Backscatter (5 or 10 MHz longitudinal wave transducer), in these methode the % of Backscatter is proportional to % of H2 damage.
3- Atenuation of 4 back eco compared with a sample without H2 damage.

It is necesary to use all 3 methods, to garantee tha it is a H2 damage.

Good look
Jairo Humberto Guzman


 
 Reply 
 
Anthony J. Egan
Consultant,
USA, Joined Nov 2001, 5

Anthony J. Egan

Consultant,
USA,
Joined Nov 2001
5
08:10 Jan-05-1999
Re: tofd applications for hot hydrogen attack on carbon steel
Regarding the original query relating to TOFD methods for detecting high temperature hydrogen attack (HTHA) in carbon steels.

Thorough review of the equipment history, material, HP pressures and operating parameters is required.

The initial screening technique should be advanced ultrasonic backscatter technique (AUBT). This technique can be used to screen the problem or questionable areas of the material. The results of the screening can determine the areas that should be investigated further. This is probably one of, if not the only method where TOFD could be used to quantify the through wall extent of the damage. However, it must be confirmed by the use of additional techniques, as follows, that the anomalies detected are indeed HTHA.

There are several analysis techniques which can be used to confirm the presence HTHA. The technique to use after the initial screening will be determined by the results of the AUBT. The progression of the analysis is dependent on the results from AUBT. For example, velocity ratio may give anomalous results if the results (indications of HTHA) from the AUBT are very close to the ID surface of the test material.
Each of the following techniques, Velocity Ratio, Spatial Averaging and Spectrum Analysis, has its most accurate results if applied in the correct progression from the initial screening.

There are several procedures that may be applied, but care must be taken in the application of the procedures as all of these techniques are very dependent on the technicians knowledge and experience.



 
 Reply 
 
M.K. Mukhopadhyay
M.K. Mukhopadhyay
09:03 Oct-30-2001
Re: tofd applications for hot hydrogen attack on carbon steel
1. Regarding the original query relating to TOFD methods for detecting high temperature hydrogen attack (HTHA) in carbon steels.

: Thorough review of the equipment history, material, HP pressures and operating parameters is required.

: The initial screening technique should be advanced ultrasonic backscatter technique (AUBT). This technique can be used to screen the problem or questionable areas of the material. The results of the screening can determine the areas that should be investigated further. This is probably one of, if not the only method where TOFD could be used to quantify the through wall extent of the damage. However, it must be confirmed by the use of additional techniques, as follows, that the anomalies detected are indeed HTHA.

: There are several analysis techniques which can be used to confirm the presence HTHA. The technique to use after the initial screening will be determined by the results of the AUBT. The progression of the analysis is dependent on the results from AUBT. For example, velocity ratio may give anomalous results if the results (indications of HTHA) from the AUBT are very close to the ID surface of the test material.
: Each of the following techniques, Velocity Ratio, Spatial Averaging and Spectrum Analysis, has its most accurate results if applied in the correct progression from the initial screening.

: There are several procedures that may be applied, but care must be taken in the application of the procedures as all of these techniques are very dependent on the technicians knowledge and experience.




 
 Reply 
 
Dr. Patel
R & D, Consultant to Universities/Industries
Fallon Ultrasonics/McMaster University, Canada, Joined May 2001, 20

Dr. Patel

R & D, Consultant to Universities/Industries
Fallon Ultrasonics/McMaster University,
Canada,
Joined May 2001
20
05:27 Oct-31-2001
Re: tofd applications for hot hydrogen attack on carbon steel
: 1. Regarding the original query relating to TOFD methods for detecting high temperature hydrogen attack (HTHA) in carbon steels.
.
: : Thorough review of the equipment history, material, HP pressures and operating parameters is required.
.
: : The initial screening technique should be advanced ultrasonic backscatter technique (AUBT). This technique can be used to screen the problem or questionable areas of the material. The results of the screening can determine the areas that should be investigated further. This is probably one of, if not the only method where TOFD could be used to quantify the through wall extent of the damage. However, it must be confirmed by the use of additional techniques, as follows, that the anomalies detected are indeed HTHA.
.
: : There are several analysis techniques which can be used to confirm the presence HTHA. The technique to use after the initial screening will be determined by the results of the AUBT. The progression of the analysis is dependent on the results from AUBT. For example, velocity ratio may give anomalous results if the results (indications of HTHA) from the AUBT are very close to the ID surface of the test material.
: : Each of the following techniques, Velocity Ratio, Spatial Averaging and Spectrum Analysis, has its most accurate results if applied in the correct progression from the initial screening.
.
: : There are several procedures that may be applied, but care must be taken in the application of the procedures as all of these techniques are very dependent on the technicians knowledge and experience.
.
I agree with above comments. We were able to measure surface properties with combinnation of sound waves and able to achieve hydride concentraion on pressure tube. If you are interested than you can send us small specimen and we can send you images. The method is complicated as we are imaging the material based velocities and works. Below is the address if you decide to send the sample for evaluation.

Regards

Dr. Patel
Fallon Ultrasonics Inc.
3 Benemar Court
Hamilton, Ontatio
Canada L8W 2R1


 
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