There are real evolutions in the old and proven Non Destructive Testing (NDT) methods such as PT and MT. The most recent of these is certainly the adoption of UV-A light-emitting diode (LED) lamps.
(Public) standards such as EN ISO 3059, ASTM E3022 and (private) specifications such as AIRBUS AITM 6-1001-12 or Rolls Royce RRES 90061 have addressed and dealt with the subject: the framework of new LED lighting tools, their descriptions, definitions, verifications and uses.
Players, users and suppliers, have therefore worked in entities such as AFNOR (French standardisation association), COFREND (French confederation for NDT) and ASTM (American society for testing material) to improve practices, particularly in lighting and in the monitoring of NDT processes by means of artificial defects.
Reminder: what is the difference between a standard and a specification in Non Destructive Testing?
The STANDARDS (e.g. ASTM E3022, EN ISO 3059 on lighting in NDT) are the result of sectoral or multi-sectoral working groups with a diverse representation of stakeholders. The SPECIFICATIONS are most often written by the principals (private entities), such as those published by RollsRoyce RRES 90061 or AIRBUS AITM 6-1001-12, which take up the edicts of the standards and/or replace the standard.
In the field of UV-A NDT penetrant lighting:
The current AIRBUS AITM 6-1001-12 specification incorporates elements of ASTM E3022;
The specification ROLLS ROYCE RRES 90061 replaces ASTM E3022.
1/ Specification RRES 90061
The RRES 90061 specification is a Rolls Royce specification that has been in existence since 2014. It concerns more specifically the control of UV-A LED sources for non-destructive testing. The RRES 90061 takes into account the geometrical and spectral aspect of the UV-A beam.
The advantages of RRES 90061
Thermal management is a parameter taken into account.
The main wavelength of a UV-A LED varies with temperature. A lock stops the UV emission if the temperature is too high.
This electronic lock prevents control with a non-conforming beam. (example centeredleo at 371 nm instead of 365 because of heat).
The geometrical aspect of the beam is imposed
A gradual decrease from the centre to the edge is described.
The controllers get used to a more or less identical beam regardless of the lamp manufacturer (as with the old PAR38 mercury bulb).
The use of a Wood filter is imposed, its characteristics are not given.
Disadvantages of RRES 90061
The human factor and visual ergonomics can be improved because the progressive decrease of the UV-A beam is ‘bordered’ in only one way: the wide beam is privileged, but the wide beam is not…
Very wide beams may be compliant but they are not suitable for small parts being tested on a MT bench.
The brightly lit bench pan turns fluorescent green (magnetic powder deposits) and floods the operator’s vision with green.
The stray violet emission of the UV-A beam is not addressed at all.
The UV-A irradiance at 38 cm has its limits, and this is important at any distance from the lamp to the room.
BABBCO/Spectro-UV Compliant Products RRES 90061
Spectro-UV’s UVISION range is compliant with RRES 90061.
Each of our lamps is delivered with its certificate.
2/ Specification ASTM E3022
ASTM E3022 is a standard for manufacturers. It covers lamp performance testing procedures: to ultraviolet A (UV-A),
light-emitting diode (LED) light sources used in fluorescent penetrant testing and magnetic particle testing.
The first version is ASTM E3022-15, released in 2015, revised in 2018 with ASTM E3022-18. In particular, it takes into account the geometry and spectrum of the beam.
Advantages of ASTM E3022
The “visual ergonomics” aspect is open, and left to the discretion of each manufacturer.
An area of minimum dimension illuminated by the UV-A beam is imposed for hand lamps at 38 cm.
The geometry of the UV-A beam is open: the manufacturer can propose very wide or narrower beams depending on the parts to be inspected (this is the advantage of LEDs that the beam can be shaped according to their position and the arrangement of the lenses).
Consideration of the limitation of violet in the UV-A beam with a standard transmission of the Wood filter.
There is no UV-A irradiance limitation at 38 cm. This allows for a more powerful beam that can be used in high “lamp/part distance” configurations (case of large parts swings / clusters of parts for example).
Disadvantages of ASTM E3022
ASTM E3022 is a manufacturer’s standard: it has no major drawbacks. However, it has been taken over by aircraft manufacturers. AIRBUS partially takes it over in AITM 6-1001-12:
Adoption of the principle of cross-scanning of the UV-A beam by the inspectors (radiometer with measuring aperture less than 0.5 inches according to ASTM E3022 §6.1).
No notion of imposed distance, only the criterion at 5000µw/cm² of UV-A is taken up at the distance lamp/part, which is even more pragmatic than the 38cm and widens the panel of usable lamps.
ASTM E3022 “high intensity” lamps with more than 5000µw/cm² at 38cm can be used at the usage distance which can be more than 38cm and at which there is 5000µw/cm² in UV-A
BABBCO/Spectro-UV products conform to ASTM E3022 (AITM6-1001-12)
Spectro-UV lamps conform to ASTM E3022 and AITM6-1001-12
All Spectro-UV SBLC (Super Black Light Compliant) and HC (High Intensity) versions comply with ASTM E3022, and ASTM E3022-18 Certificates of Conformity are provided with.
Other BABBCO/Spectro-UV products according to ASTM E3022 and AITM6-1001-12
For the radiometer, the modified versions of the Accupro and Accumax in version A are suitable for cross – scanning of the UV-A beam.
Classic / “A” versions (in line with ASTM E3022 with reduced sensor aperture for more accurate beam scanning)
3/ Other standards and specifications
3.1 The EN ISO 3059 Standard “conditions for observation”.
The EN ISO 3059 standard “conditions for observation” applies to inspections by
Magnetic resonance imaging
EN ISO 3059 specifies the minimum requirements for illumination by UV-A sources and measurement. It does not apply to actinic blue sources. EN ISO 3059 is under revision at the time of writing. It will be a standard with an obligation of results (the obligation of means is rather dedicated to specifications) and will take into account :
Visual ergonomics (violet emissions, transverse and longitudinal geometric aspects, in the manner of a scan carried out using an ultrasound beam),
Measurement: definition and characterization of radiometers (and luxmeters), and metrology
UV-A light and in particular the definition of the performance of LED lamps.
The advantages of EN ISO 3059
Simplicity and pragmatism are the key words
The UV-A radiation (the ‘black light’) is evoked, the white light is also treated with the associated qualitative and quantitative indices (colour rendering index, colour temperature, UV spectrum, etc.).
The distance from the lamp to the workpiece does not matter, it is the effective illumination that is important on the inspected surface.
The disadvantages of EN ISO 3059
Too simple in view of the new LED products
The characteristics of the measuring instruments are insufficiently regulated. The revision currently being drafted will fill these gaps.
We discover why and how the beam geometry influences the PODs (probabilities of detection), aspects of light ambient variation due to the age of the controller and some more advanced notions of metrology for the management of the radiometer and luxmeter fleet.
The publication of CEN/TR 17108 is concomitant with that of CEN/TS 17100, both publications being part of the CEN (European Committee for Standardization) documentary base.
An example of ergonomic adaptation in video:
Advantages of CEN TR 17108
simply addresses the subject of vision and ergonomics in NDT.
is the basis for developing the CEN/TS 25107 training programmes and understanding the importance of visual ergonomics in NDT.
3.4 The Technical Specification CEN/TS 17100
CEN/TS 17100 (TS for Technical Specification) describes:
how to make the reference photos required for standard default panels (NiCr Tesco, Penetrant System Monitoring 5*, New-Reference panel NR5*)
what are the tools and means to achieve this.
The process is in 2 steps:
When taking a picture of the panel (the reference photo), a resolution test pattern is used to check that the picture is taken correctly (no moving fluo or focusing error often existing under UV-A),
A resolution pattern on the printout attests to the high-definition quality of the paper output.
Digital image correction processing is allowed for:
removing chromatic aberrations often present in ultraviolet photography,
minimizing geometric aberrations where they exist.
Visualization of the result and use on the screen is also allowed.
The techniques resulting from traditional PT and MT (more than 50% of COFREND certificates and certifications) are highly trusted. However, some criticisms appear to be that the human factor is too important in detection probabilities.
Recently developed and published standards and specifications are the answer for professionals to integrate new tools, especially those related to lighting. They make the measurement reliable, whether it is made by radiometer or luxmeter, or even in metrology.
BABBCO offers you not only its services and products, but also its recognised expertise in Non Destructive Testing. You will thus be able to capitalize on experience and equipment while adopting the most advanced standards and techniques.
Alain CARTAILLAC-Moretti Area Manager France South COFREND Expertise PT AFNOR expertise A09b WG4