|Rolf Diederichs |
NDT.net, Germany, Joined Nov 1998, 603
Near field operation by use of Hardface probes
Hello Mr. Splitt,
Today is your day!
I hope you will get a lot of questions.
Sound propagation is part of our program, so I have a question about this.
Hardface probes are designed to operate in direct contact method.
The probes doesn't have inside a delay, actually they are immersion
probes providing a wear resistance protection layer.
The physics of sound beam showing that within the near field
many interferences, by means of maxima and minima of the sound preasure.
Because of this interferences I am concerned if this technique could be used.
My further questions are.
1. Can I do a proper flaw detection
2. Need the indications a special interpretation
3. Can I use it for wall thickness measurements with no problem
4. Could you explain something general about the nearfield operation, also with immersion
R & D, -
Private, Germany, Joined Nov 1998, 38
Re: Near field operation by use of Hardface probes Near field operation by use of hardface probes
Hello Mr. Diederichs
Thank you for your first questions in this workshop.
Measuring in the near field zone of probes seems to be a critical task. Fortunately due to the definite bandwidth of the probes the modulation of the field is not so severe as for monofrequent probes. With a broad band probe the maxima and minima are smoothed out.
1. Flaw evaluation
1.1 DGS method
As documented by the DGS curves in the Krautkramer probe data sheets, flaw evaluation in the near field is possible. The shortest distance between probe and flaw is only limited by the ringing of the probe after the transmitter pulse (near resolution).
1.2 Reference reflector method
With this method you can evaluate any flaw in comparison to a reference reflector without knowing details about the sound field structure.
2. Special interpretation
In both cases you have to keep in mind that in the near field range the maximum flaw indication generally is off axis, i.e. you will detect a small reflector two or more times when you scan the probe transverse to the flaw position.
3. Wall thickness measurement
For wall thicknes measurement in the near field range we need high resolution / broad band probes. As the reflector (back wall echo) normally exceeds the sound beam cross section the sound field modulation will be averaged. Therefore, the wall thickness measurement is not influenced by the near field structure.
4. The above explanations are not restricted to hardface probes but are genarally valid for all types of probes.
|Rolf D. |
NDT.net, Germany, Joined Nov 1998, 603
Re: Near field operation - a further discussion Hello Mr. Splitt,
Hello Workshop participants,
thanks for your answer, however I have still some more questions
regarding the near field operation.
"With a broad band probe the maxima and minima are
smoothed out", what will be the dB figure approximately?
Further you said
"...you will detect a small reflector two or more times
when you scan the probe transverse to the flaw position."
That actually means that the sound pressure curve isn't so
much smoothed out as you said it before. Or is there just a minima at the
I remember while adjusting a probe on a pipe I received
at two positions a maxima echo amplitude, if
entry echo or backwall echo I don't remember.
My question is:
In what position should the probe be adjusted?
If I use a maxima the probe will not stand in the 'correct' angle to the
pipe axis. The application is a wall thickness measurement
as well as a flaw detection.
By the way, here a hint for the Germans.
Mein Englisch ist auch nicht vom Besten, ohne ein
Spell check program für meine englischen Texte wäre ich aufgeschmissen
Sehr gut eignet sich der Spell Anywhere von GIR software.
Ich hatte ihn früher mal über CompuServ geladen. Dieses
oder ähnliches ist aber sicherlich auch im Internet zu beziehen.
GEKKO, Standard and Advanced phased-array for Easier inspection
With a 64-channel parallel architecture, GEKKO is a flaw detector
offering at the same time conven
tional UT, standard PAUT, TOFD and
real-time Total Focusing Method (TFM). GEKKO improves the
detection, with better defects characterization
and sizing as well as for misoriented defects.
Some procedures require standard UT, others TOFD or PA. GEKKO
includes all these techniques to offer a versatile and field-ready
- 64:64 parallel channels
- + 4 additional TOFD
- Conventional UT channels
- International code compliance: ASME, AWS, API, ASTM, ISO-EN
Watch the video: https://youtu.be/kuEY_RwWS3Q
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
Ultrasonic tomograph for imaging of concrete structures А1040 MIRA
Applicable for concrete inspection allowing imaging of the internal
structure of objects from conc
rete, reinforced concrete, different
stones. The operation applies pulse-echo technique at one-side access
to the object. The instrument is feasible for concrete inspection for
searching conduct ducts, conduits, detection of foreign inclusions,
holes, honeycombing, cracks and other concrete defects.
Navic - Steerable Modular Automated Scanner
The Navic is a modular, motorized, steerable scanner designed to
carry multiple attachments
in various scanning and inspection applications. The Navic is
capable of weld scanning
(girth welds and long seam welds), automated corrosion mapping,
and tank scanning.