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- since 1996 -
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Technical Discussions
Cherie
NDT Inspector,
USA, Joined Sep 2013, 15

Cherie

NDT Inspector,
USA,
Joined Sep 2013
15
12:45 Oct-08-2013
OD indication interpretation

Good morning,

What would cause an indication reflector in the OD gate which isn't visible and doesn't hold powder?

Thanks,

Cherie

    
 
 Reply 
 
Mario Talarico
NDT Inspector,
Italy, Joined May 2010, 411

Mario Talarico

NDT Inspector,
Italy,
Joined May 2010
411
18:47 Oct-08-2013
Re: OD indication interpretation
In Reply to Cherie at 12:45 Oct-08-2013 (Opening).


Cherie,
might be a planar discontinuity deep enough to escape the surfaces control but close enough to the surface to create a corner from which its reflection.
It happens often.
greetings
mario






    
 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
19:58 Oct-08-2013
Re: OD indication interpretation
In Reply to Cherie at 12:45 Oct-08-2013 (Opening).

- Undercut
- Misalignment
- Weld cap
- Dissimilar thickness

Try wet MT instead of powder, sometimes helps.Check the parent metal wall thickness at the point of the indication, if it is thicker there may be a sub-surface defect present.

    
 
 Reply 
 
andrew cunningham
NDT Inspector
Canada, Joined Jun 2008, 238

andrew cunningham

NDT Inspector
Canada,
Joined Jun 2008
238
21:06 Oct-08-2013
Re: OD indication interpretation
In Reply to Cherie at 12:45 Oct-08-2013 (Opening).

What angle probe are you using? A 60 can and will misplace O and ID connected reflectors. To eliminate non relevant surface reflectors from reflectors that propagate into the sample you are testing, spray a low viscosity liquid onto the surface. As the liquid flows, all surface reflectors will move with the liquid is irrelevant. Any reflector remains static will be subsurface, and therefore need assessing. (I use a pump spray bottle and or WD40)
If you are still undecided use Wet MT or try PT if nothing shows

All the best

    
 
 Reply 
 
Trent
NDT Inspector,
Canada, Joined Sep 2012, 13

Trent

NDT Inspector,
Canada,
Joined Sep 2012
13
16:01 Oct-09-2013
Re: OD indication interpretation
In Reply to Jon Wallis at 19:58 Oct-08-2013 .

Yep like Jon said try a black on white contrast wet MPI sometimes picks up better

    
 
 Reply 
 
Trent Steffen
NDT Inspector,
Canada, Joined Sep 2012, 13

Trent Steffen

NDT Inspector,
Canada,
Joined Sep 2012
13
16:09 Oct-09-2013
Re: OD indication interpretation
In Reply to Trent at 16:01 Oct-09-2013 .

Dry particles range from
50um (0.002 inch)
150um (0.006 inch)

Wet particles range from
0.1um (0.000004 inch)
10um (0.0004 inch)

    
 
 Reply 
 
Cherie
NDT Inspector,
USA, Joined Sep 2013, 15

Cherie

NDT Inspector,
USA,
Joined Sep 2013
15
12:48 Oct-10-2013
Re: OD indication interpretation
In Reply to Trent Steffen at 16:09 Oct-09-2013 .

Thank you all for replying...

The angle is appropriate for the thickness. I was thinking midwall, but didn't understand why it was showing up in the OD gate. I'm familiar with wet mag, but am only accustomed to seeing OD indications. How would a midwall present itself using this technique?

Cherie

    
 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
18:44 Oct-10-2013
Re: OD indication interpretation
In Reply to Cherie at 12:48 Oct-10-2013 .

Not sure I understand you....
If your gate is set at the OD then it can only trigger indications appearing at the OD surface. Why do you think that this indication might be a midwall defect?

    
 
 Reply 
 
Cherie
NDT Inspector,
USA, Joined Sep 2013, 15

Cherie

NDT Inspector,
USA,
Joined Sep 2013
15
00:37 Oct-11-2013
Re: OD indication interpretation
In Reply to Jon Wallis at 18:44 Oct-10-2013 .

It didn't hold powder and the thickness gauge reading was .040"-.110" on a .450" wall pipe.

    
 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 180

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
180
13:15 Oct-11-2013
Re: OD indication interpretation
In Reply to Cherie at 00:37 Oct-11-2013 .

A planar discontinuity just below the OD surface. Not enough surface to break the lines of force in the magnetic particle direction but enough surface to reflect ultrasound from the thickness measurement orientation.

Regards,
Gerald

    
 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
17:46 Oct-12-2013
Re: OD indication interpretation
In Reply to Cherie at 00:37 Oct-11-2013 .

Sorry, I have to work in metric.
Nominal wall thickness is 11mm but thickness measurements give readings between 1mm and 2,8mm. As Gerald says, this is probably a sub-surface defect. Can you grind the surface to try ans make the indication surface breaking? If you're examining material (not a weld) it may be a lap that breaks the surface at a position further away than your area of magnetic examination.

    
 
 Reply 
 
Andreas
NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh, Germany, Joined Oct 1999, 129

Andreas

NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh,
Germany,
Joined Oct 1999
129
05:08 Oct-13-2013
Re: OD indication interpretation
In Reply to Jon Wallis at 17:46 Oct-12-2013 .

Hallo Cherie ,
have the indication any dimension , like moving the probe left/right and forwards/backwards.
Get you signal also from the otherside of indication.
When you check the wall thickness ,was it hard to find the spot with the wall reduction.
As you asked before about OCTG wallthickness mesurements , what type of pipe you inspecting and in which area you find the flaw.

Regards

Andreas

    
 
 Reply 
 
Cherie
NDT Inspector,
USA, Joined Sep 2013, 15

Cherie

NDT Inspector,
USA,
Joined Sep 2013
15
00:34 Oct-14-2013
Re: OD indication interpretation
In Reply to Andreas at 05:08 Oct-13-2013 .

Thank you all for responding...

I believe it was a midwall close to the surface and I may have been looking at 3rd leg. It happened again on the same string. 1st leg was so close to the IP and I believe I missed it on the one I originally questioned.

    
 
 Reply 
 
Mario Talarico
NDT Inspector,
Italy, Joined May 2010, 411

Mario Talarico

NDT Inspector,
Italy,
Joined May 2010
411
22:48 Oct-14-2013
Re: OD indication interpretation
In Reply to Cherie at 00:34 Oct-14-2013 .

Cherie,
should be possible to establish with reasonable certainty if you are in presence of a reflection midwall deflected by comparing the expected skip distance from a surface reflection with the current carried out.
In your case ( midwall reflection), there should be an important difference between the two measures (despite a similar path).
A figure from you help understand more.
greetings
Mario

    
 
 Reply 
 
Cherie
NDT Inspector,
USA, Joined Sep 2013, 15

Cherie

NDT Inspector,
USA,
Joined Sep 2013
15
03:55 Oct-15-2013
Re: OD indication interpretation
In Reply to Mario Talarico at 22:48 Oct-14-2013 .

Mario,

Thank you. I understand what you're saying, but I can't locate a list of sound path distances specific to the OD and thickness. I've been trying to solve the equation for angle beam circumferential scanning, but have been having trouble. My employer wont get me a IIW block, so I don't know if my equipment is reading true (otherwise, I would have been able to determine if it were a mid wall based on SD). Again, thank you. I sincerely appreciate your advice :)

    
 
 Reply 
 
Andreas
NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh, Germany, Joined Oct 1999, 129

Andreas

NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh,
Germany,
Joined Oct 1999
129
18:43 Oct-15-2013
Re: OD indication interpretation
In Reply to Cherie at 03:55 Oct-15-2013 .

Cherie ,
so you looking for longitudial defects now , so there is a factor to be consider for the skip distance.
The soundpath will be longer , if you inspect in circumference direction of pipe.
For transverse defect on a pipe you can apply the standard laws and formulas,
For longitudinal defects can you can not apply them.
You must have a testpiece with ext and int notches to set up the unit , with the some wallthickness and Outside diameter.
I aking myself you really understand what you are doing.

Regards

Andreas

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1266

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1266
15:25 Oct-16-2013
Re: OD indication interpretation
In Reply to Cherie at 03:55 Oct-15-2013 .

zoom image
Cherie, you have quite a few replies to this posting but all are speculating. Andreas has effectively identified the problem...a lack of information.
You provide no information about the component or the ultrasonic setup until your third posting when we learn that you have been working on a pipe with 11.4mm wall (0.450”) and you seem to have done a confirming inspection to locate an indication using a thickness meter to gauge the distance to the upper tip as 1mm to 3mm from the outer surface. We have no indication of the pipe diameter and no indication of the angle-beam details other than you state “The angle is appropriate for the thickness”. You have indicated that you are using ID and OD gates...but no details on the placement targets (did you use a notch on each surface and then extend the gates a specified distance either side?). How did you calibrate for range using the “appropriate angle” without a calibration block?
When Andreas noted that you are apparently looking at a longitudinally oriented flaw in the cylinder, the issues now make more sense. But it is not clear how you would have calibrated the gate positions unless you had the necessary targets.
I uploaded an image from the new Civa 11 to indicate how significant some of the factors can be on the positioning of a signal in the A-scan. I modelled a 12.5mm diameter 5MHz probe on a 45° refracting wedge. I placed rectangular flaws 1x10mm in plate and pipe sections 11.4mm thick and scanned over the targets with the beam perpendicular to the flaw long axis. The probes are modelled to provide the exact same wedge distance to the exit points but I made the probe for the plate flat and the probe for the pipe contoured to match the 150mm diameter that I decided to make it (you did not provide the pipe diameter either). For this illustration I opted to use the target that I modelled with a 1mm ligament. Such a planar flaw would probably not be detected by AC MPI.
The important item to note is that with all the settings being equal for the probe, the soundpath to the peak signal in the plate is 27.3µs and the same flaw in the pipe is 30.6µs. On the A-scan on the right side of the image I overlaid the indication as it would appear from the pipe on the gated signal in the plate. If you calibrated your A-scan in millimetres this would represent about 5.3mm (or about 0.21 inch) difference. The path back to the probe for the peak signal is not likely to be a simple straight line return from the flaw surface along the incident path. Instead, there will most likely be a tandem effect off the pipe surface due to the subsurface nature of the flaw. Therefore, if you are assuming a soundpath distance to the “OD Gate” based on plate and not on a real calibration block, the potential for error is significant.
    
 
 Reply 
 
CHERIE
NDT Inspector,
USA, Joined Sep 2013, 15

CHERIE

NDT Inspector,
USA,
Joined Sep 2013
15
04:36 Oct-17-2013
Re: OD indication interpretation
In Reply to Ed Ginzel at 15:25 Oct-16-2013 .

I was trying to get a general idea of what to look for....quickly. I don't have the luxury of time nor a supervisor who understands the physics of ultrasonics...much less knows API standards. Had you noted the comment where I stated I have "0" calibration equipment, perhaps you could have assumed I was doing the best I could with limited resources as opposed to assuming I was stupid.

    
 
 Reply 
 
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation, USA, Joined Jun 2012, 140

Albert

Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140
06:57 Oct-17-2013
Re: OD indication interpretation
In Reply to CHERIE at 04:36 Oct-17-2013 .

Cherie,

Lots of the people on here are well respected subject matter experts in their respective fields. Most of them post, share, and help only in the interest of helping others. I doubt Ed made any assumptions about you other than the information you originally provided was a bit unclear as to the exact application, reference being used and with what equipment.

Ed was more considerate and helpful than most of the persons I've dealt with as far as taking the time to give a through response with pictures and what not.

Next time you post try to provide all the info, the who what when where why and with what and I'm sure you will have a totally different experience.


Just keep posting and you'll see that in this forum you have access to an almost infinite amount of knowledge, expertise, and willingness from total strangers to help without any compensation for their efforts.

Best of luck with your current project.

ALM

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1266

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1266
12:55 Oct-17-2013
Re: OD indication interpretation
In Reply to Albert at 06:57 Oct-17-2013 .

Thank you Albert. Indeed this is the case. We have seen posts complaining about the detailed and pedantic replies that some of us provide. Perhaps these lengthy replies are not wanted by those posting the query. But when limited information is available it is very difficult to provide the "quick" answer.

    
 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 180

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
180
14:20 Oct-17-2013
Re: OD indication interpretation
In Reply to Ed Ginzel at 12:55 Oct-17-2013 .

I have been in this business for only 33 years so far. I wish I had the resources avaiable to me from forums such as this throughout my career. Fortunately, I worked with some very knowlegable people and gained alot of valuable experience.

There are no questions that I would consider as too low to warrant a response. We all lack knowledge and experience in some situations. Even as a Level III there are ocassional discussions on these forums that I have to research and keenly think about. Add to this, the fact that these forums are global in reach and language can be diffucult to understand. Take the ENglish language. It is spoken in many places around the world but, all locations have a unique flavor of English. In the USA where I live, we have problems of understanding between different areas of the country because of the way English is used.

Please feel free to ask your questions and if I can provide some valuable input, I will.


Regards,
Gerald

    
 
 Reply 
 
Amy
NDT Inspector, - -
USA, Joined Jan 2009, 87

Amy

NDT Inspector, - -
USA,
Joined Jan 2009
87
14:30 Oct-17-2013
Re: OD indication interpretation
In Reply to Ed Ginzel at 12:55 Oct-17-2013 .

Ed,
I thought your response, as well as many others, were very good and well detailed. Please continue to post the technical and lengthy responses, as it gives those of us looking for other possible variables a fresh eye.


Cherie, I'm glad you found your solution and good luck to you. I would mention that there are many NDT companies out there and if your supervisor/company is not providing the tools and proper equipment to meet procedures and codes you may want to look at other options in the field. This is your name and certification that goes with the exam you are performing.

    
 
 Reply 
 
Andreas
NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh, Germany, Joined Oct 1999, 129

Andreas

NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh,
Germany,
Joined Oct 1999
129
20:11 Oct-17-2013
Re: OD indication interpretation
In Reply to Ed Ginzel at 15:25 Oct-16-2013 .

Hallo Ed ,
nice work to explain.
Cherie is inspecting pipes acc API she tell us later on.There different types of pipes and therefore different standards.
We till now have not the info about OD , the ratio of ID to OD you defined the angle you must used when looking for longitudinal defects.She was trying to solve a formula for circumferential scanning.
We still have not all infos to solve her problem.
i do myself work like that and you need to have test pipe with int/ext notches normally 5% of nominal wall depth , 1/2" long and 4/1000" width , orientation of notches are acc to requirement of the spec.
With the notches you make a DAC curve on your unit and any indication that is higher will be a reject.Before you reject anything you must check the DAC curve.

Regards

Andreas

    
 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
20:47 Oct-17-2013
Re: OD indication interpretation
In Reply to Albert at 06:57 Oct-17-2013 .


I fully endorse your views on Mr. Ed Ginzel. I have great reverence for his expertise and age.

I started doing UT in 1969 and did hundreds of castings, welds and thousands of forgings. I did have many research facilities when I was working with BHEL.

But now that I am on my own I only have the necessary instruments for doing some commercial testing.

I find that Ed has some real good tools for studying the given problem and comes out with focused answers, sometimes they have to be elaborate and lengthy lest the issue is not fully justified.

That is the reason I avidly read Ed's replies, for the rich technical content and clarity they give. I learn something new every time I read his replies.

Wishing everybody well

P V SASTRY

    
 
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