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Is increasing UV-A irradiance the right answer to a high luminance in the inspection booth?

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Written by Administrator
Sunday, 12 May 2013 07:44

June 2013

Paper presented at the 2011 COFREND Convention on NDT, May 24-27, 2011, Dunkirk (France).

Available in French on:
• The COFREND Website
• The NDT Website

An abstract of this paper was published in the "Avis d’Experts" (Editor’s note: Experts’advice), pp 71-77, in the N° 41 – December 2012 issue of the quarterly Review Contrôles Essais Mesures, Editocom publishing, 11 Allée Jacques Decour, F-93270 Sevran (France),

This publication is a supplement to, and an update of the original conference.

1- Introduction

In the February 2010 Penetrant Professor issue(1), William E. MOOZ wrote a chapter on "UV and white light" as follows:

"There is little or nothing written from a technical point of view concerning the question of how much white light is acceptable during inspection with fluorescent penetrants.

We are planning to publish a technical discussion on this subject in the near future which will directly address this subject and also the idea that one is able to compensate for excessive white light by increasing the intensity of the UV-A.

We have enlisted the expertise of our good friends Patrick DUBOSC and Pierre CHEMIN to not only give this subject scientific depth but an international flavor.

We will be publishing excerpts from their in-depth paper."


The question asked by a user of fluorescent penetrants comes as follows:

"I use UV-A sources giving a 15 000 µW/cm² irradiance, well above the 1000 µW/cm² minimum required. As an illuminance figure of 20 lx (2 fc) maximum is allowed along this minimum, could I have a 30 lx (3 fc) figure when using 15 000 µW/cm²?"


A very similar question was asked by the German members of the European Technical Committee (TC) 138, Working Groups (WG) 4 and 5, of the CEN, the European Committee for Standardization many years ago, when the ISO 3059:2001 standard "Non-destructive testing -- Penetrant testing and magnetic particle testing - Viewing conditions", was designed as a European standard before becoming an ISO standard.

This paper details some technical reasons that explain why such an idea is wrong.

Penetrant Testing and Magnetic Particle Testing are NDT methods which shall be processed as per specifications, standards, codes, etc.

Nobody can do without!

Measuring visible light in the PT/MT UV-A booths dates back to the late ‘80s(2).

Later large primes and NDT bodies defined tougher specifications for viewing conditions in PT/MT booths. As examples:
• A minimum illuminance figure for inspection using colour contrast products.
• A minimum (and sometimes also maximum) irradiance figure for inspection under UV-A irradiation.
• A maximum acceptable illuminance due to visible light in areas of inspection under UV-A irradiation.
• Acceptance of combined radiometers/luxmeters

Combined digital radiometer/luxmeter simultaneously
displaying illuminance and (UV-A) irradiance figures.

Some clues of the ISO 3059:

• Inspection in white light: 500 lx minimum ON THE SURFACE under inspection. The Americans require at least 1,000 lx.

• Inspection under UV-A irradiation:

> An irradiance higher than 1,000 µW/cm² and a MAXIMUM of 5,000 µW/cm² for PT applications.

> An illuminance (visible light) lower than 20 lx on the surface under inspection, all the UV-A sources switched "ON", at the working distance. The "real working conditions" mean that measurement shall be carried out with the same surface/UV-A source(s) distance/location as those used for inspection, that curtains, if any, shall be as they are when parts are inspected, etc. The visible light may come from the UV-A sources or from other sources ("light leaks" in the roof/curtains, etc.). Measurement done in the real working conditions duplicates the REAL inspection situation! This is simpler, more useful, more reliable than any of the other complex procedures in which the user tries to measure the visible light from UV-A sources in artificial conditions, then, measures the visible light coming from any other point.

> UV-A irradiance on the parts at the washing station (fluorescent penetrant testing) shall be 300 µW/cm² minimum while the visible light illuminance on the parts shall be lower than 150 lx.

2- A manufacturer who wanted the standard to meet his UV-A source technical data

The first UV-A source fitted with a µ-xenon discharge bulb(3) was marketed in Europe in 1998.

The visible light level given by this source was much too high.

The manufacturer, therefore, did his best so that the ISO 3059 standard meets his UV-A source technical data. You are disbelieving? Nevertheless, that’s not a joke!

He used the following reasoning: let us make the ratio: minimum acceptable UV-A irradiance measured at 15’’ (38 cm)/maximum acceptable (visible light) illuminance measured at 15’’ (38 cm).

Using these figures he got a figure: 1,000/20 = 50 µW/(cm² lx) or 50 µW cm-2 lx-1.
[according to the rule of writing unit symbols of the International System of Units (SI).]

(As the ISO 3059 standard states that illuminance shall be less than 20 lx, the maximum acceptable figure is 19.99 lx!)

He went to the conclusion that keeping this same ratio whatever the UV-A irradiance or the visible light illuminance would allow for the right viewing conditions.

Hence, he wrote that a UV-A source giving a 5,000 µW/cm² irradiance could come along a 100 lx illuminance. By the same token, a 1,400 lx illuminance would be acceptable along with a UV-A irradiance of 70,000µW/cm².

This manufacturer was completely unaware of the "saturation effect" or of the fluorescence fading under a high UV-A irradiance(4).

An incredible situation!

As a matter of fact, this ratio based on two physical units has really no meaning at all.

Let us take an example: the ratio of length vs time: speed. This ratio has some meaning, unless …

A sprinter runs 100 meters in ca 10 seconds. Keeping the same value of this ratio, i.e. 10 m/s, it would mean that he could run 10,000 meters in 1,000 seconds, i.e. 16 minutes and 40 seconds. In fact, the world record is currently 26 minutes 17 seconds and 53/100. Don’t you feel as if there is a misconception?

Some ratios have a physical meaning, i.e. are based on physics. Some have not. However, even for this example about speed, a factor has not been put in the equation: the physiological answer of a living body to a long effort. A cheetah may run up to 112 km (69.6 miles)/h but only for very few hundreds of meters/yards. Then, if the prey escapes, the cheetah gives up.

The situation is similar with the irradiance/illuminance ratio: no consideration for the way the human vision works, even if putting aside the saturation effect and the UV-A fading of penetrants !

This point alone makes us understand that this manufacturer was not at all an expert on the topic, or that, at least, he tried to find a selling point for his units, which did not meet the requirements.

At that time, Patrick DUBOSC and Pierre CHEMIN both protested against this manufacturer - successfully.

3- How do human eyes work

3.1- Rods and cones. Adaptation to illuminance changes

The retina comprises three areas: one which is about 10% of the surface, in the center of the retina, is made of cone-shaped cells, hence their name. Almost 90% of the surface of the retina is made of long cells, the rods. And a very small surface has no light sensitive cells at all: the "blind-spot" where all the axons (the "nerve fibers") of all the cells gather and go to the brain. This schematic as described here is very simple; the way the light-sensitive cells are connected to the brain is a bit more complex!

The cones give information about the colour of the light received by the retina. There are three types of cones, one for three different colours, but not the three fundamental ones. Cones need quite a high level of light to give information. When the eyes are in a low-illuminance area, the cones give no information at all.

Physical structure of human retina
Rods, cones and nerve layers in the retina. The front (anterior) part of the eye is on the left. Light (from the left) passes through several transparent nerve layers to reach the rods and cones (far right). A chemical change in the rods and cones send a signal back to the nerves. The signal goes first to the bipolar and horizontal cells (yellow layer), then, to the amacrine cells and ganglion cells (purple layer), then, to the optic nerve fibres. The signals are processed in these layers. First, the signals start as raw outputs of points in the rod and cone cells. Then, the nerve layers identify simple shapes, such as bright points surrounded by dark points, edges, and movement. (Based on a drawing by Ramón y Cajal.)
(Source
Wikipedia)

Then, the rods come into action. Human eyes are among the most sensitive ones in the animal world, though many are those who think the other way! Rods do not give information about colour, only about the "intensity" of light. Rods work perfectly when there is a low level of light, while the cones do not give information. That’s why "all cats are grey in the dark."

When going from a lowly illuminated area to, say, a workshop, or in plain sunlight, suddenly the rods get far too many photons. They are saturated, and can no longer give usable information. The cones need about 30 to 60 seconds to give usable information to the brain: this is the time needed for the cascade of chemical reactions due to the photons to take place creating a depolarization signal (a kind of electrical signal) which goes from the cells to the brain at a speed of 300 m/s. During this adaptation period the eyes are unable to work properly.

In the other way, when going from, say, sunlight or even a workshop to a dimmed-lit area, say, a UV-A inspection booth, suddenly the cones no longer receive enough photons to give usable information to the brain, while the rods stay "saturated" with metabolites (chemicals produced by the degradation of other molecules) for some time, one to five minutes, depending on the difference of light levels, and also on the age and on the medical "history" of the people. During this adaptation period one cannot perform an accurate job, though the eyes’ performance improves within some minutes.

A five-to-ten-minute adaptation time is generally required, but in the ASTM E1417/E1417M, Standard Practice for Liquid Penetrant Testing, paragraph 7.6.1 Type I Processes: "Inspector’s vision shall be dark adapted for a minimum of 1 min prior to examining components."

Though written in the § 8.6.2.1 of the ISO 3452-1:2008 standard, the five minute adaptation time is almost never enforced.

Further, the inspector's age or even diet, which may ease or not the desaturation of the rods, have an influence on his (her) adaptation time.

These adaptation periods are very tiring for the eyes + brain system.

That’s why any NDT method where important changes of illuminance occur requires the inspector to wait for some time: PT, MT, VT but also when reading RT films, etc. Another point to think about: as these adaptations are tiring, MUCH BETTER to have inspectors performing a 2-hour shift in the UV-A inspection booth, then having 10 minutes for a coffee-break, and back to the booth, instead of seeing inspectors who go out of the booth to get parts, then enter the booth, begin immediately their inspection, then five or ten minutes later, go out for a set of other parts, etc.

3.2- Sensitivity to colours

The human eyes have their maximum sensitivity at a wavelength of 550 nm when the cones work. This is a photopic condition. In very low illuminance areas, when only the rods work, the maximum is at 505 nm. This is a scotopic condition. In between, this becomes a mesopic condition.

550 nm is yellow. 505 nm is green. Don’t you see the reason why fluorescent penetrants are green? Why the green ones have generally a higher sensitivity than the yellow ones?
The human eyes are far less sensitive to the blue side (short wavelengths), and still more especially to the red side (long wavelengths) of the visible spectrum. So the question by PT users may be: "But almost all the colour contrast penetrants are red, some orange, some, purple: if the human eyes are so poorly sensitive to the red, then, why colour contrast PT is so good?"

Go to the following paragraph for the answer!

3.3- Sensitivity to contrasts

Our eyes have a very interesting capability: detection of contrasts. For example, a white line is easily seen against a black background - or the other way. However, a green line is not easily seen against a faint green background.

In a very interesting paper(6), Yves MISEREY explains how researchers have understood how eyes see contrasts (the difference between bright areas and dark areas of the visual field). The size of the pupil is of the utmost importance then, but something makes it more complex: pupil’s size for similar conditions varies from one person to the next and, for the same people, depends on illuminance, distance and age.
Further researchers checked how people wearing goggles see contrasts; the target is to design progressive lens adapted for everyone, to be as close as possible to the natural vision. "This task is complex, as the eye scans the entire surface of the lens," underlines Gilles Le Saux, Director of research for Essilor.

How to define the contrast?

To make it very simple: a perfectly white surface would reflect 100% of the incident photons.
A perfectly black surface would absorb 100% of the photons, and reflect 0%.

So if one calculates the white/black ratio, we would have an infinite ratio. In fact, the "whitest" surface which is known reflects about 97% of the photons. The “blackest” one reflects about 3%, though some years ago, in a laboratory, researchers went down to less than 0.1%. However, we are talking here about day-to-day processes.

The ratio comes now to 97/3, very close to 32. In fact, this is the best ratio we could achieve when using colour contrast products. "But Sir, wait for a while: PT uses not black penetrants, but red ones: why, and what about the ratio?"

Good question!

Why? Penetrants designers know well how to design black penetrants. However, in an industrial environment, black, or very dark colours, are quite common, when the red is uncommon. Further, there is a psychological factor: red is the colour of blood and also a distinctive mark for: hazard, risk, fault, error, rejection, etc. Therefore, the inspector’s attention is likely to be more attracted by red than by black.

And what about the ratio? Well, first, very good white developers have a reflecting factor of about 94%. The 97% figure can be achieved only by magnesium oxide, which is not good as a developer - though a small quantity is often put in the formula.

Red dyes may give about 10%. The ratio comes to 94/10: 9.4. By experience, a ratio of 6 at least is necessary when looking for tiny things: sewing, tiny cracks, etc. The lower the contrast ratio, the longer the work, the worst the results: the user gets tired very quickly, his efficiency becomes dubious.

In penetrant testing, if there is a small reddish background, or if the developer used is more grayish than white, the contrast ratio dramatically falls.

What is the situation when using fluorescent materials (penetrants, magnetic particles)?

In fact, the background should be almost invisible. The photons come from the indication: exactly the reverse of the previous paragraphs.

Then the background reflects very few photons. Assume that its figure is 0.1%. Assume that the indication has a factor of 70 (we will not discuss here where it comes from, but it is close to the truth). The ratio is then: 70/0.1, i.e. 700!

When we compare this to the 9.4 almost impossible to get with colour contrast PT, one may begin to understand why using fluorescent indicators leads to far easier inspection, far more reliable, far quicker for a better probability of detection (POD)! And trust us when we say that a ratio of 700 is very easy to get. In fact, in the aerospace industry, on PT lines, we may go up to 5,000 when all the line parameters are rightly set, depending on the surfaces (rough surfaces generally give a lower figure).

If we round up 9.4 to 10 and consider that a 1,000 ratio is common with fluorescent penetrants, we could say that we can detect a quantity of dye about 100 times smaller than with contrast PT in the best conditions!

3.4 Ability to detect aligned indications

Another very interesting ability of the old system: human eyes+ human brain is the detection of aligned indications. Within ¼ of a second, an experienced inspector is able to decide that several small indications, which taken one by one, would be within the acceptance criteria, are in fact only one far longer indication, which overcomes acceptance criteria. This cannot be duplicated by any artificial vision-computer combination, especially if parts are complex, if there is some coloured or fluorescent background on the part.

All of this makes us understand that the millennia-old "obsolete", portable, free of any electrical plug or battery connection, system known as the human visual system is irreplaceable. That’s why it is so important to understand how it works.

4- Fluorescent indications

Fluorescent indications seem to glow intensely. In fact, the number of photons emitted by an indication is quite low and in FINITE quantity. We perceive it as glowing by contrast with the almost invisible background. However, when "ambient" photons of any kind of light arrive on the retina, they dramatically lower the contrast ratio, hence, the seeability of the indication, the capability of the inspector to detect it, especially if it is tiny.

That is a major reason for the standards, specifications, etc., requiring a low level of light in the inspection booth.

We could add that it is not sufficient to measure the "ambient" light, but that a measurement should be done also at the inspector’s eyes' position where they will be placed when inspecting.

5- High intensity UV-A sources vs visible light

5.1- Visible light vs white light

A very common confusion is displayed even in specifications or some standards.

White light is … white.

Visible light is … visible: that means it can be blue, green, orange, whatever, as far as it can be seen by the eyes.

In UV-A inspection booths, there is an unusual amount of visible light, as many sources (except LEDs) emit many radiations in every colour of the visible spectrum. The Wood’s filter blocks many wavelengths, but let quite a fair amount of blue light go through. When the eyes are in scotopic or mesopic conditions (in UV-A inspection booths, they are in mesopic conditions), given that the sensitivity curve goes to the short wavelengths, human eyes become far more sensitive to the blue radiation than in photopic conditions. That’s why it is more than a good idea to wear goggles, which blocks the UV-A radiation but ALSO which blocks the blue wavelengths. Doing so, the eyes are no longer disturbed by the blue photons: contrast ratio is increased, the inspector works in better conditions.

So, what about the "ambient white light measurement?" What about using luxmeters which sometimes are not that sensitive to the blue radiation (they should comply with the CIE standard curve as shown on the following figure, but a lot of them do not).

All the documents should state the visible light, and not the white light. If we were auditors, if we see there is no white light in the booth, we would tick our audit form: "No white light", even if there is a huge amount of blue light in the booth due to high intensity UV-A sources!

This could happen! Very high intensity UV-A sources are used, either as handheld units, or as overhead sources. We talk of something in the 15,000 to 30,000 µW/cm² range on the parts! These sources emit photons at thousands of wavelengths, but do not give a "white light" when a Wood’s filter is used - happily, there is always a filter. So, as a first point, documents should refer to "visible light".

We will see later in this paper other adverse effects of very high intensity UV-A sources.

5.2- UV-A radiation and cataract

Known since decades is the relation between UV-A eyes’ exposure and cataract: lens lose their transparency, and shall be removed and replaced by an artificial lens, or not replaced. The higher the UV-A intensity, the longer the exposure, the quicker the cataract. That is a major reason ALWAYS to wear UV-A blocking goggles when under UV-A: in inspection booths, but also in sunlight, when skiing, at the sea-side even when the sun is diffused by clouds, etc.

5.3- UV-A radiation and blue haze

When UV-A radiation enters the eye (by reading the previous paragraph, this should never occur for our readers!), there is an instant reaction: the aqueous humour, the gel between the lens and the retina, contains many organic molecules, used to feed the eyes' cells or which are metabolites (degraded molecules, "waste" to summarize it in a word). Almost all these molecules fluoresce when exposed to UV-A. That means visible photons of any colour are produced INSIDE the eye. Many of them will go to the retina, giving information to the cones. This information has nothing to do with what is seen. It blurs the useful information and produces what is known as the "blue haze". A very uncomfortable situation indeed, which is prevented when wearing UV-A blocking goggles.

6- Irradiance/illuminance ratio: comparing potatoes and carrots

As seen previously in chapter 2, the irradiance/illuminance ratio has no meaning for our NDT applications. The main point here is that even a small amount of visible photons has an adverse action on the ability of the inspector to detect the indications. To prevent such a detrimental action, the best way is to stay stubborn with the requirements which have proven, along the years, they help users to perform their duty reliably in the right conditions.
Stating that increasing visible light by a parallel increase of the UV-A irradiance would offset any detrimental effect on the inspector’s performance is not in accordance with what we know about the eyes.

The only true ratio to be taken into account is: the ratio of the illuminance emitted by the fluorescent indication/the illuminance emitted by the fluorescent background. This ratio is a dimensionless quantity.

7- High irradiance and dyes

Further, test carried out ca 1986, but not published then, by Patrick DUBOSC, then active in BABBCO, France, showed that when exposed to a UV-A irradiance above 5,000 µW/cm², the fluorescent yellow, green-yellow or green dye used in penetrants saturates while the optical brightener continues to increase its emission. This leads to indications going to a bluish, then bluish-whitish, then whitish aspect as long as the UV-A irradiance increases. These colours give a lower contrast ratio with the background, which becomes more and more visible, due to several factors: the surface reflects more visible photons; the metal shines; the tiniest traces of unremoved penetrant fluoresce as whitish-bluish. Therefore, not only indications are no longer green, or yellow, or yellow-green, but the contrast is impaired.

8- High irradiance and UV-A fading

Another detrimental effect is that some dyes used in "low-cost penetrants" fade when exposed even 15 minutes only to high UV-A irradiance sources. This is just the time for a coffee-break. Parts left exposed on the table will be "accepted" when the inspector is back, even if unacceptable cracks exist. This should not occur with penetrants listed in the Qualified Products List (now the Database) of the SAE-AMS 2644 American specification. However, the tests of ultraviolet stability of the fluorescence have not been performed under very high intensity as those claimed by UV sources manufacturers!

(5) Induced Fade of Penetrant under 10 200 µW/cm² (UV-A) irradiance
Initial appearance            After 15 minutes
100% Brightness               9% brightness
(Photograph published with the kind permission of Richard LOPEZ, Senior Materials Engineer
John Deere – Moline Technology Innovatio
n Center Moline, IL, USA)

(5) UV-A microscope images showing indication luminance as observed before (left) and after (right) a 60 minute exposure to 20,000 μW/cm2; also noted is the amount of time (5.5 minutes) required to effect a 50% reduction in illuminance
(0.040” long lcf crack).
(Photograph published with the kind permission of Richard LOPEZ, Senior Materials Engineer
John Deere – Mol
ine Technology Innovation Center Moline, IL, USA)

9- High irradiance and safety

Another concern is about safety. Patrick DUBOSC made tests with a renowned French dermatologist working as an expert in European groups for standardization on safety of tanning equipment - - finally he disapproved using any tanning equipment.

Everyone has a different phototype: very white (people from Northern Europe), white (a lot of Europeans and North Americans), almost tanned (South Europeans, people from Northern Africa, Middle East), yellow (Asians), black (Africa, Aborigines in Australia, Indians, Sri Lankans), red-haired people. As an average, everyone, due to his (her) day-to-day life, receives 250 MED (minimum erythemal doses) of UV-A from the sun. MED is not a unit as a kilogram, or a meter, or an hour. Everyone has his own susceptibility to UV (A and B). The MED is the dose that induces an erythema on one’s skin, i.e. when the skin becomes reddish when exposed. Therefore, the MED is different for everybody.
These 250 doses come when we are walking to buy bread - or croissants! - in the bakery, when we are walking to the Metro station. Some workers get more than the average 250 doses, those who work mainly outside.

We can get 250 additional MED a year without trouble, as long as they are split almost equally along the months. However, when exposed to the sun during skiing or on the beach at summertime, this averaging no longer exists. Further, it is likely that the 250 MED additional level will be exceeded. This is the first step to malignant melanoma, one of the deadliest cancers.
This dermatologist came with us in plants to measure the doses received by the hands of operators. To summarize, he let us know that an exposure to 5,000 µW/cm², 7 hours a day, 5 days a week, 40 weeks per annum, would lead to the 250 MED.

The fact that this 5,000 µW/cm ² figure is found here and in the introduction (about the ISO 3059 standard) is purely coincidental. Nevertheless, this is an additional reason not to go too high in UV-A irradiance A.

Further, generally, when very high intensity UV-A sources are used, they are put as overhead sources. That means the top of the head is very close to the UV-A source. The UV-A level is very, very high. Many experienced inspectors are men in their 40s or 50s. For hormonal reasons, quite often, these inspectors are bald, or at least their hair is very thin. Thus, their skin has no protection. The scalp skin is very thin. We always recommend, when overhead sources are used, even if not very powerful, that people wear a cap.

This cap is not worn to prevent men to become bald (we have "learned" during our numerous contacts, that "an inspector must wear a cap in a UV-A inspection booth because UV-A make men bald!" A distortion of what they were told!), but to prevent far more serious consequences.

10- So what to do?

Obviously, we recommend:

• Use sources which give 5,000 µW/cm² maximum on the surface under inspection. If you use several sources, this figure must be held when all the sources are in service.

• Add ambient UV-A sources such as luminescent tubes: this to prevent the eyes of the operator continuously going from an area well lighted with UV-A and some visible light to areas much less lighted, when having for instance, to fill in a report.

• Less than 20 lx (2 fc) on the surface under inspection AND ON THE INSPECTOR’S EYES LEVEL. Better to have less.

• Design the PT/MT line so that the inspector is not constantly going into and out of inspection booth.

• The inspector shall wear UV-A and blue-light blocking goggles.

• The inspector shall wear clothes with long sleeves; gloves when possible; a cap when overhead UV-A sources are used.

- Never use photochromic spectacles (which become brown, or even black, when exposed to the sun; in fact, it is not the sun light which makes them darken…it is the UV-A!)

• Do not wear clothes that fluorescence under UV-A (the beautiful white coat lab, the fancy T-shirt, etc.).

Well, now, back to the original question: users would be better checking that working under an illuminance of 32 lx (3 fc) does not jeopardize their inspection under a UV-A irradiance of 15,000 µW/cm². These tests should be carried out not only on reference blocks, referred to as Known Defects Standards (KDS) in many American specifications, but on real parts, with tiny flaws in difficult-to-inspect areas. Nevertheless, we cannot recommend such a way of performing inspection. There are many reasons, which underpin the figures and the technical data stated in the ISO 3059:2001 standard , that a daily experience in thousands of UV-A inspection booths the world over reinforces.

A pretty new, exciting and fascinating work project for Lisa BRASCHE (Airworthiness Assurance Center of Excellence, Institute for Physical Research and Technology), Iowa State University, Ames, IA, USA ... if she gets funds for that!


References

(1) William E. MOOZ: UV and White Light, The February 2010 Penetrant Professor from MET-L-CHEK®: on this Website.

(2) Patrick DUBOSC and Pierre CHEMIN: A reminiscence of ultraviolet radiation and visible light measurement: on our Website.

(3) Pierre CHEMIN and Patrick DUBOSC: Penetrant testing history: on our Website.

(4) Patrick DUBOSC and Pierre CHEMIN: Tomorrow’s penetrants, DPCNewsletter N°019- Décember 2009: on our Website.

(5) Rick LOPEZ: Induced Fade of Penetrant and FPI Indications – CASR - Center for Nondestructive Evaluation Iowa State University, USA: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

(6) Yves MISEREY : Les recherches sur les lunettes de plus en plus poussées (editor’s note : More and more thorough research on goggles), Le Figaro (French daily newspaper), week 11, 2010.


Normative references

• ISO 3059:2001, Non-destructive testing -- Penetrant testing and magnetic particle testing - Viewing conditions, International Organization for Standardization, Geneva, Switzerland, 2001.

• ISO 3059:2012, Non-destructive testing -- Penetrant testing and magnetic particle testing - Viewing conditions, International Organization for Standardization, Geneva, Switzerland, 2012.

• ISO 3452-1:2008, Non-destructive testing -- Penetrant testing -- Part 1: General principles, International Organization for Standardization, Geneva, Switzerland, 2008.

• ASTM E1417/E1417M, Standard Practice for Liquid Penetrant Testing, ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA, 19428-2959, USA, 2011.

• SAE-AMS 2644E, Inspection Material, Penetrant, Society of Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale, Pennsylvania 15096, USA, 2006.

Last Updated ( Sunday, 12 May 2013 10:23 )