Ethics and Best-Case Analysis
In "Erratic Measure," (Republished in the May issue of NDTnet) Ronald Christensen and I point out that the flaw detection methods of today violate the Unit Measure axiom of probability theory. Ethical questions follow from this, for the violations invalidate value-free methods for estimating the probabilities of error, leaving only value-laden methods.
In designing things, engineers often employ the method of analysis which is worst, from the standpoint of cost but best, from the standpoint of safety. This is called "worst-case analysis." Engineers don't usually employ best-case analysis. However, in estimating the probability of detection (POD), the NDT community employs best-case analysis.
The question of whether to use best-case or worst-case analysis arises when a test is positive for a flaw and the positive relates to more than one flaw. That this relation is one-to-many violates Unit Measure and invalidates probability theory. However, Unit Measure can be preserved and probability theory restored by selecting a flaw and counting it as detected while counting all of the other flaws as not detected. A value judgement is made in selecting the flaw. Thus, this method of analysis is value-laden.
Under best-case analysis, the largest of the flaws is selected. Under worst-case analysis, the smallest of them is selected. Best-case analysis provides an upper bound on the POD of large flaws and a lower bound on the POD of small flaws, while worst-case analysis provides the opposite. Thus, best-case analysis makes NDT look better than it is while worst-case analysis makes it look worse.
The use of best-case analysis without warning is ethically striking under any circumstances but this is particularly true when the organization employing it is a safety regulator. Nonetheless, studies published by the U.S. Nuclear Regulator Commission ("Steam Generator Group Project. Task 13 Final Report: Nondestructive Examination Validation.," NUREG/CR-5185, 1988. U.S. Nuclear Regulatory Commission, Washington, DC.) and the U.S. Federal Aviation Administration ("Reliability Assessment at Airline Inspection Facilities, Violume III: Results of an Eddy Current Inspection Reliability Experiment." DOT/FAA/CT-92/12, III, Federal Aviation Administration, Washington, DC) use best case analysis. Neither agency warns the readers of its report that the POD estimates are the result of best case analysis.
For more than 14 years, I've observed that the NDT community displays no, discernable interest, in modifying its practices to preserve Unit Measure and have always wondered why this is. Here is a theory. If the NDT community were following custom in engineering, by using worst-case analysis in estimating the POD, it could make NDT look better by modifying it to preserve Unit Measure. However, in reality, the NDT community is using best-case analysis and failing to warn people of the departure from custom. It follows that the NDT community would make NDT look worse by modifying it to preserve Unit Measure. Is thiswhy I can't find an interest in preserving Unit Measure?
SONOAIR - air-coupled Phased Array Ultrasonic Inspection System
For highly attenuating materials, the performance of the system is critical. The ultrasonic sensors,
the scanning area and the system settings should be flexibly adapted to the test task and the material.
These high expectations are met with the new and modular testing system SONOAIR. With the world’s first air-coupled phased-array UT inspection system SONOAIR we developed a technology that works with up to 4 transmitter and receiver channels with freely configurable square wave burst transmitters as wells as low noise receiving amplifiers.
Digital Radiography for Concrete Inspection
In the construction industry (buildings, bridges) there is a need for fast non-
most commonly to locate targets (Pipes, Re-bars, Conduit,
Fittings etc.) within concrete structures prior to drilling, cutting or coring.
Measuring reinforcements is also performed for static calculations and to detect
corrosion problems and damages. Cracks and voids can also be visualized. The
examinations are not only restricted to concrete constructions; they can also be
applied to reinforced masonry made of natural stones or bricks.
Next generation for Phased Array UT is here now with FMC/TFM! Have higher
resolution imaging, impr
oved signal to noise ratio, characterize, size and analyze
defects better with access to several wave mode views and save raw FMC data for
higher quality analysis. Some of the benefits are:
- Beautiful Image! Easier to understand what you're looking at
- Completely focused in entire image or volume
- Much easier to define setups before inspection
- Easier to decipher geometry echoes from real defects
- Oriented defects (e.g. cracks) are imaged better
- See image from different wave modes from one FMC inspection
- FMC data can be reprocessed/analyzed without going back to the field
TVC awarded UKAS accreditation
TVC are delighted to finally announce we have been awarded UKAS
accreditation for our calibration
Laboratory accreditation to ISO/IEC 17025:2005 enables us to
conduct the Electrical Verification of Ultrasonic Flaw Detection
Equipment to BS EN 12668-1:2010. It has taken many months of hard
work and we want to thank our staff for all their efforts during
this massive undertaking.