Introduction
Penetrant Testing is a widely used method which allows for the detection of open
and surface breaking discontinuities on: all metallic materials, numerous mineral
materials (glass, ceramics) and, after satisfactory compatibility test, some organic
materials.
The main advantage of this non destructive testing method lies in the fact that all
these defects can be detected, with a total reliability, whatever are:
- Their direction.
- Their position on part.
- The size and the complexity of the part under test.
Penetrant Testing can be used almost anywhere, except under water, using few items.
It also allows to carry out the inspection, in automatic process lines controlled
by programmable controllers, of large runs of components such as: blades, suspension
arms, etc. and this at a lower cost.
Few methods offer such a flexibility and such a versatility.
Although ‘’Intellectual Guides’’ were able to announce the death of Penetrant Testing
before the horizon of the year 2000, Penetrant Testing nevertheless stays alive and
is the first method (after Visual Testing, however) which precedes all the other
methods of Non Destructive Testing.
Now, it is not the fact of the fate. Along the years, Penetrant Testing always integrated
the technological developments, both in chemistry and in physics, which came one
after one.
It is interesting to finger out that Penetrant Testing is a global method. It means
that it is possible to inspect a part in a single process with this method, when
that cannot even be thought about with Ultrasonic or Eddy currents Testing.
Some points of thinking:
- Which other Non Destructive Testing method allows to detect, on the leading edge,
on the trailing edge or on the christmas tree foot of tens of thousands of turbine
blades (for aeroengines or gas turbines) checked every day in the world, the discontinuities
of 1 micrometer of opening, 10/15 micrometers deep, 300 micrometers long ?
- Which other method may be used on titanium or ceramic prosthesis as well as on
polyimide (a synthetic material used in some aircraft parts) parts, etc, to detect
open to the surface discontinuities just for 20 to 30 cents per part ( excluding
personnel costs)?
- Nanotechnologies have been a premium for some years. Penetrant Testing is a pioneer
in this domain!! Indeed, a crack of the size mentioned for the turbine blades, is
going to trap at best some tens of nanograms of fluorescent dye, that the "obsolete
detection " system, that is the eye + human brain set (sensor + signal processing
device), is going to detect in a fraction of second and interpret in some seconds.
All this without electronics, without battery, without being connected to a computer!
Regrettably, a lot of people who do not know much about the requirements of Penetrant
Testing, impose requirements which we cannot meet. A very current example: in refineries,
one " forbids using flammable products ", wants "especially no aerosols propelled
with flammable gases ". The Safety Service writes it as an essential requirement.
When we come to carry out a red dye penetrant inspection, a volatile, nonhalogenated
solvent cleaner, thus easily flammable or very flammable, will be needed. A developer
having a volatile carrier, nonhalogenated thus easily flammable, will be needed;
so that the applied coating is in accordance with the Penetrant Testing requirements,
it is necessary to use a LIQUEFIED gas, nonhalogenated for metallurgical reasons;
thus some butane-propane, extremely flammable.
The Penetrant Testing story is not thus ended!
Who, nowadays, knows best the history of Penetrant Testing ?
If this history appears in a certain number of works, it is always in an inaccurate
or indistinct way and, mostly, incomplete.
What is the reason?
First of all, all the precursor developments were not recorded, because, in these
times, means of distribution of knowledge and works were comparable in no way to
today’s.
Many Engineers, who worked on Penetrant Testing, have passed away or left their job
without recording any of these improvements
Pierre CHEMIN and Patrick DUBOSC, two physico-chemist Engineers, actively worked
in Penetrant Testing since the end of the 60s. They noted all the developments until
our days, while participating in it.
Indeed, throughout their professional career, they were in a privileged position,
being at the interface between users and manufacturers of products,equipments and
accessories.and the users.
Actors, Trainers, Authors of numerous publications and Speakers, they were the best
expertised to write the history of Penetrant Testing which you will find displayed,
below, in a synoptic way, in tabular form.
Do not hesitate to contact us to give us of your comments and to ask for additional
information.
