where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
1417 views
Technical Discussions
ranjeet singh
Engineering, Asst.Manager-Condition Monitoring
TATA chemicals ltd.(fertilizer div.), India, Joined May 2006, 6

ranjeet singh

Engineering, Asst.Manager-Condition Monitoring
TATA chemicals ltd.(fertilizer div.),
India,
Joined May 2006
6
02:37 May-05-2006
Variance in ECT results during tube inspection of stripper

We are operating Fertilizer plant at India.During Annual Turn-round 2006 one of our vertical exchanger stripper's tubes were inspected by using eddy current test .
Details of heat exchanger is as follows,
Falling film type vertical heat exchanger
Media in the tube-Ammonium carbamate
Materail of tube-Titanium gr-3
Results of eddy current were very surprising as it was found more than 60% gradual wall loss in more than 25% tube.Management had started thinking about its replacement in the coming year.As it was surprsing that after 10 year of operation results were such.But then it was decided to pull ot one of the tube to check ECT worthiness.
After pull out it was inspected from inside/outside and pieces were cut to measure its bore using bore gauge.Measurement showed that reduction is not more than 40%.
Also its wall thickness was measured using ultrasonic thickness gauge,whcih also confirmed the bore gauge results.
Calibartion tube and its artificail flaws were made as ASME section-V.
ECT instrument was confirming the calibartion tube but not exchanger tube.
I would like to no possible reasons,which caused such deviation.





 
 Reply 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 524

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
524
05:56 May-06-2006
Re: Variance in ECT results during tube inspection of stripper
Without Knowing the precise details of the test it is difficult to be sure where the error appears.

Howvever I presume that

1) You are using an absolute/external reference test at a frequency appropriate to the wall thickness.

2) Calibration and Reference Tubes closely match the Ti alloy used in the Heat exchanger.

3) Your calibration tube is representative, I.e. it contains long areas of wall reduction of say 20, 40 and 60% - Not just narrow grooves.

Even so, large even wall loss is often difficult to measure with Eddy current, since with an absolute test any variations through the tube (e.g de-alloying / heat effects etc, although this shouldn't occur with Ti) will be indistinguishable fromm wall thickness variations. 60 vs 40 % loss is not too far away from what might be considered a typical level of experimental error. It is always usfeul to have a backup method such as IRIS available to verify this type of problem.

Joe


----------- Start Original Message -----------
: We are operating Fertilizer plant at India.During Annual Turn-round 2006 one of our vertical exchanger stripper's tubes were inspected by using eddy current test .
: Details of heat exchanger is as follows,
: Falling film type vertical heat exchanger
: Media in the tube-Ammonium carbamate
: Materail of tube-Titanium gr-3
: Results of eddy current were very surprising as it was found more than 60% gradual wall loss in more than 25% tube.Management had started thinking about its replacement in the coming year.As it was surprsing that after 10 year of operation results were such.But then it was decided to pull ot one of the tube to check ECT worthiness.
: After pull out it was inspected from inside/outside and pieces were cut to measure its bore using bore gauge.Measurement showed that reduction is not more than 40%.
: Also its wall thickness was measured using ultrasonic thickness gauge,whcih also confirmed the bore gauge results.
: Calibartion tube and its artificail flaws were made as ASME section-V.
: ECT instrument was confirming the calibartion tube but not exchanger tube.
: I would like to no possible reasons,which caused such deviation.
:
:
------------ End Original Message ------------




 
 Reply 
 
Ranjeet
Engineering, Asst.Manager-Condition Monitoring
TATA chemicals ltd.(fertilizer div.), India, Joined May 2006, 6

Ranjeet

Engineering, Asst.Manager-Condition Monitoring
TATA chemicals ltd.(fertilizer div.),
India,
Joined May 2006
6
06:17 May-08-2006
Re: Variance in ECT results during tube inspection of stripper
Dear Mr.Joe,
Thanks for sharing your valuable comments,
You can assume there was no error in the instrument (TX4200 Tes tex USA make and 4X2 eddy current sys) as test was repeated by using another different m/c(TX2000).Test were conducted Insitu by inserting probe in ID side & using Differential,Absoulte and Multi freq.probes ie.4 channel and 2 frequency.Inst has the capability of detection of flaws in the tube(pitting,cracks) and determination of tube thickness in %.Calibration standards were fabricated on fresh tubes of same dimensions and mt'l ie Ti Gr.3 as per ASME sec V article 8 Appendix.1
On inserting probe in the calibration tube it was forming wave form as expected.
calibration tube is representative, I.e. it contains long areas of wall reduction of say 20, 40 and 60% - Not just narrow grooves.And also our calibration tube is representative, I.e. it contains long areas of wall reduction of say 20, 40 and 60% - Not just narrow grooves.
We are suspecting problem in the tube materail ie its thermal conductivity and magnetic permeabilty might have changed being in service for 10 years.And ECT depends on these properties.We got this particular pulled out tube piece analysed
matellurgiucally and found that TiH2 has formed .Its micrograph shows long flake thread like of TiH2 .
Now we want to confirm whether TiH2 can effect ECT results.


----------- Start Original Message -----------
: Without Knowing the precise details of the test it is difficult to be sure where the error appears.
: Howvever I presume that
: 1) You are using an absolute/external reference test at a frequency appropriate to the wall thickness.
: 2) Calibration and Reference Tubes closely match the Ti alloy used in the Heat exchanger.
: 3) Your calibration tube is representative, I.e. it contains long areas of wall reduction of say 20, 40 and 60% - Not just narrow grooves.
: Even so, large even wall loss is often difficult to measure with Eddy current, since with an absolute test any variations through the tube (e.g de-alloying / heat effects etc, although this shouldn't occur with Ti) will be indistinguishable fromm wall thickness variations. 60 vs 40 % loss is not too far away from what might be considered a typical level of experimental error. It is always usfeul to have a backup method such as IRIS available to verify this type of problem.
: Joe
:
: : We are operating Fertilizer plant at India.During Annual Turn-round 2006 one of our vertical exchanger stripper's tubes were inspected by using eddy current test .
: : Details of heat exchanger is as follows,
: : Falling film type vertical heat exchanger
: : Media in the tube-Ammonium carbamate
: : Materail of tube-Titanium gr-3
: : Results of eddy current were very surprising as it was found more than 60% gradual wall loss in more than 25% tube.Management had started thinking about its replacement in the coming year.As it was surprsing that after 10 year of operation results were such.But then it was decided to pull ot one of the tube to check ECT worthiness.
: : After pull out it was inspected from inside/outside and pieces were cut to measure its bore using bore gauge.Measurement showed that reduction is not more than 40%.
: : Also its wall thickness was measured using ultrasonic thickness gauge,whcih also confirmed the bore gauge results.
: : Calibartion tube and its artificail flaws were made as ASME section-V.
: : ECT instrument was confirming the calibartion tube but not exchanger tube.
: : I would like to no possible reasons,which caused such deviation.
: :
: :
------------ End Original Message ------------




 
 Reply 
 
Ikesh Patel
Ikesh Patel
03:32 Jun-18-2006
Re: Variance in ECT results during tube inspection of stripper
Dear Mr.Ranjeet
Can you please tell me the material on the shell side and also the dimensions of the tube as well as your technique of inspection , I mean to ask differential and absolute and weather with impedance plan or only with stri chart ? Your calibration tube is from the same heawt treatment lot or is it differ ? Can you pls send me the calibration detail and the signal capture you are getting from the defect?
Thanks.
Ikesh Patel
(ISNT ET III)


 
 Reply 
 
Ranjeet singh
Ranjeet singh
09:45 Jun-30-2006
Re: Variance in ECT results during tube inspection of stripper

Dear Mr.Ikesh Patel,
Plz.also find attached my clarification to Mr.Joe.
Material of shell is CS
Size of tube:27 ODX 3.5 thick
Equip.used Tes tex made TX2000 4x2 Eddy Current Tester and also TX 4200
Modes-differential,Absolute and multi frequency 4 channel , 2 frequency.
Calibration tube was new but of Ti gr-3.
I am sending seperately scan of calibration and defects waveform to your mail.

Thanking you,

Regards,

Ranjeet

Dear Mr.Joe,
Thanks for sharing your valuable comments,
You can assume there was no error in the instrument (TX4200 Tes tex USA make and 4X2 eddy current sys) as test was repeated by using another different m/c(TX2000).Test were conducted Insitu by inserting probe in ID side & using Differential,Absoulte and Multi freq.probes ie.4 channel and 2 frequency.Inst has the capability of detection of flaws in the tube(pitting,cracks) and determination of tube thickness in %.Calibration standards were fabricated on fresh tubes of same dimensions and mt'l ie Ti Gr.3 as per ASME sec V article 8 Appendix.1
On inserting probe in the calibration tube it was forming wave form as expected.
calibration tube is representative, I.e. it contains long areas of wall reduction of say 20, 40 and 60% - Not just narrow grooves.And also our calibration tube is representative, I.e. it contains long areas of wall reduction of say 20, 40 and 60% - Not just narrow grooves.
We are suspecting problem in the tube materail ie its thermal conductivity and magnetic permeabilty might have changed being in service for 10 years.And ECT depends on these properties.We got this particular pulled out tube piece analysed
matellurgiucally and found that TiH2 has formed .Its micrograph shows long flake thread like of TiH2 .
Now we want to confirm whether TiH2 can effect ECT results.

----------- Start Original Message -----------
: Dear Mr.Ranjeet
: Can you please tell me the material on the shell side and also the dimensions of the tube as well as your technique of inspection , I mean to ask differential and absolute and weather with impedance plan or only with stri chart ? Your calibration tube is from the same heawt treatment lot or is it differ ? Can you pls send me the calibration detail and the signal capture you are getting from the defect?
: Thanks.
: Ikesh Patel
: (ISNT ET III)
------------ End Original Message ------------




 
 Reply 
 

Product Spotlight

ISAFE3 Intrinsically Safe Sensor System

ISAFE3 intrinsically safe sensor system of Vallen Systeme is especially targeted at the petrochemica
...
l - as well as oil and gas transportation industry. The sensor system is designed for permanent monitoring or periodic inspection tasks. Sensors are available for different AE-frequency ranges optimized for corrosion and fatigue crack detection and other applications. The ISAFE 3 sensor system consists of an AE-sensor (model ISAS3) certified according to ATEX/IEC for installation in zone 0, gas group IIC, IP68, 20 to +60 °C, and a signal isolator (model SISO3) certified for installation in zone 2. An ISAS3 sensor can be mounted in atmosphere or submerged, e.g. in water or crude oil. It is supported by mounting tools for temporary (magnets) or permanent (welded) installation. ISAFE3 supports automatic sensor coupling test and can be used with any AE signal processor supporting 28V supply at 90 mA peak, e.g. Vallen Systeme ASIP-2/A.
>

XRHRobotStar

In high volume industries like automotive the requirement for a hundred percent X-ray inspection c
...
reates a bottleneck in the production. The XRHRobotStar is a fully Automated Defect Recognition (ADR) capable robot-system that allows an ultra-fast in-line inspection.
>

FD800 Bench Top Flaw Detectors

The bench-top FD800 flaw detector range combines state-of-the-art flaw detection with advanced mater
...
ial thickness capabilities. Designed for use in the laboratory these gauges are the tool you need for all your flaw detecting needs.
>

NEW - TD Focus-ScanRX

The NEW Next Generation Advanced UT platform, TD Focus ScanRX - Also available as a card stack solut
...
ion. Key Improvements 1. Data acquisition is significantly faster than current design 2. Better aesthetic – closely aligns with HandyScan RX 3. Improved IP rating (Target IP66) 4. Ruggedized housing 5. Connectors are protected from impact and ingress 6. Integrated stand and separate retractable handle easy to keep clean) 7. Touchscreen with ruggedized display glass 8. 3-Axis encoder input
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window