Fluorescent dye penetrant inspection (FPI) - Visual inspection technique - Well established - Covered by several ASTM standards - E1417 - E3022 Some modern videoscopes now include a UV light source to expand how FPI is used in inspecting: - Castings - Aviation engines - Automotive frames - Many others Current standards for FPI - Inspections done at a longer distance - Use a larger light source - Where the human eye is the imaging tool

1. Fluorescent Dye Penetrant Inspections Using Videoscopes
Charles Janecka
RVI Product Applications Specialist
Olympus Corporation of the Americas
ASNT – Houston TX – October 29, 2018

2. Introduction

3. • Current standards for FPI
• Inspections done at a longer distance
• Use a larger light source
• Where the human eye is the imaging tool
Introduction
• Some modern videoscopes now include a UV light source to expand how FPI is
used in inspecting:
• Castings
• Aviation engines
• Automotive frames
• Many others
Introduction
• Fluorescent dye penetrant inspection (FPI)
• Visual inspection technique
• Well established
• Covered by several ASTM standards
• E1417
• E3022

4. A Brief History of Fluorescent
Dye Penetrant Inspection

5. • FPI — Identify very small cracks
• Forged parts after they have cooled
• Regular use (specifically at the intersection of beams and members)
• FPI often used in manufacturing and maintenance settings
A Brief History of Fluorescent Dye Penetrant Inspection

6. FPI is performed in six basic steps:
A Brief History of Fluorescent Dye Penetrant Inspection

7. FPI is performed in six basic steps:
1. Clean the material
a) Surface contaminants can impede the capillary action
A Brief History of Fluorescent Dye Penetrant Inspection

8. FPI is performed in six basic steps:
2. Apply the penetrant
a) Levels from low sensitivity to high: ½, 1, 2, 3, and 4
b) Different types will not be discussed here
c) Let it sit (dwell) for up to 30 minutes
A Brief History of Fluorescent Dye Penetrant Inspection

9. FPI is performed in six basic steps:
3. Remove excess penetrant
a) Only the dye that has crept into the cracks remains
b) Different chemicals are used depending on the type of penetrant
A Brief History of Fluorescent Dye Penetrant Inspection

10. FPI is performed in six basic steps:
4. Apply the developer (not always)
a) The developer “pulls” the penetrant out of the cracks
A Brief History of Fluorescent Dye Penetrant Inspection

11. FPI is performed in six basic steps:
5. Inspect the part
a) Inspector uses UV light
b) Cracks will glow
c) Standards are discussed later in the presentation
A Brief History of Fluorescent Dye Penetrant Inspection

12. FPI is performed in six basic steps:
6. Complete cleaning
a) The part is thoroughly cleaned to remove all penetrant
A Brief History of Fluorescent Dye Penetrant Inspection

13. • Most FPIs involve a large UV light source
• Often, the entire part is covered in penetrant and developer
• A large cone of UV is shone on the part
• Look all around the outside
• Must be in a darkened area
A Brief History of Fluorescent Dye Penetrant Inspection

14. • FPI is very effective
• Uses a large and powerful UV light source
• Covers large portions of the part
• Bright UV light makes the cracks glow at a distance
• Biggest drawback:
• Inspectors cannot see any channels or stress points hidden by the
geometry of the part
A Brief History of Fluorescent Dye Penetrant Inspection

15. Videoscopes with Ultraviolet
Capabilities

16. • Videoscopes — remote visual inspection (RVI) tool
• The ‘remote’ aspect of RVI solves the drawback of not being able to see
completely because of the geometry of the part
• Adding RVI to FPI can make the inspection more complete
Videoscopes with Ultraviolet Capabilities

17. Videoscopes with Ultraviolet Capabilities
• This enables inspection inside of a part
• The insertion tube needs to generally be
4 mm to 6 mm
• This size is the largest technical hurdle
of videoscopes
• Videoscopes use a tiny charge-coupled device (CCD) image sensor
• The CCD is at the end of a long insertion tube
• The image is translated onto a screen for the user

18. • An increase in heat increases the frequency of the electromagnetic radiation
• A human body radiates in the infrared range
• An incandescent bulb radiates in the visible light range
Videoscopes with Ultraviolet Capabilities
• Light can be electrically generated in a variety of ways
• The first light bulbs involved heating a thin material
• They approximate a black body radiator
• Anything hotter than absolute zero radiates energy

19. • We need a good CCD and enough light in a very small space
• Halogen bulbs used to generate light and then transmit it through a light guide
• They were ineffective as they lost a lot of energy to heat
• The greater the light intensity, the greater the heat
• The higher the frequency, the greater the heat
Videoscopes with Ultraviolet Capabilities

20. • Many modern videoscopes use LED lights
• Often transmitted through a light guide
• LEDs generate light through electroluminescence
• Different than black body radiation
• Generate very little heat
Videoscopes with Ultraviolet Capabilities
• Different semiconductor materials
are needed for different
frequencies
• LEDs can now generate true UV
at the intensity needed for small
spaces
https://en.wikipedia.org/wiki/Light-emitting_diode

21. • Handheld UV light sources have been in use for a long time
• Several advantages that handhelds have over videoscopes:
• There is space for a large array of LEDs
• Larger battery to meet larger LED’s power requirements
• Videoscopes do not have this space
• Videoscopes also need power for:
• The screen
• CCU
• Processor
• Memory functions
• Light source
• Articulation motors
• And other components
Videoscopes with Ultraviolet Capabilities

22. • Videoscopes can expand FPI inspections
• Videoscopes with UV lights are used in the same manner as white light
• The end is then articulated to the area of interest
Videoscopes with Ultraviolet Capabilities

23. • The UV light is projected in the same field of view as the lens
• If a crack is present, the UV light causes the crack to fluoresce
• The videoscope picks up the glowing crack
• The image is transmitted to the screen
Videoscopes with Ultraviolet Capabilities

26. Fluorescent Dye Penetrant
ASTM Standards as They Apply
to Videoscope Inspections

27. • This is all basic FPI info
• Rudimentary and academic for RVI
• The situational aspects of the system matter
• They are generally taken for granted and presumed
• RVI in FPI is very different from most historical FPI
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

28. • For most of FPI:
• An inspector uses a large and powerful UV light source
• They use the UV light several inches from the part
• They use their eyes to observe the fluorescing cracks
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

29. • When using FPI with RVI (a videoscope):
• The UV light source is not as powerful
• The insertion tube is inside the part
• The UV light only travels a couple of inches
• Any fluoresced cracks are ‘observed’ by a manufactured lens and CCD chip
assembly
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

30. • One of the biggest differences is between the human eye and the RVI imaging
system
• RVI’s lensing is smaller than the human eye
• The sensor projecting the image is also smaller
• The amount and intensity of light going through each system are different
• The light projection and imaging are directly next to each other in RVI
• The current standards presume using the human eye
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

31. • ASTM E 1417 (-99 current rev) is the standard for the procedures discussed
• It is titled “Standard Practice for Liquid Penetrant Examination”
• Within this standard, there are many sections that will not be listed here
• We will focus on the UV light and how it pertains to videoscope FPI inspections
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

32. • ASTM E1417 Paragraph 6.6.1:
• “For stationary fluorescent dye examination, Type I, the ambient visible
light background shall not exceed 2fc (20 lux) at the examination surface.
The black lights shall provide a minimum of 1000 µW/cm2 at the
examination surface. Black lights shall meet the requirements of 7.8.5.1.”
• Three concerns are noted here, and each will be addressed separately
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

33. • “[T]he ambient visible light background shall not exceed 2fc (20 lux) at the
examination surface.”
• Not an issue with videoscope inspection
• Commonly performed in the interior of a part
• If there is a concern, a simple covering can be placed over the port
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

34. • “The black lights shall provide a minimum of 1000 µW/cm2 at the examination
surface.”
• Previous revisions dictated a specific distance
• Examination distance and light projection distance are the same in RVI
• Was very difficult for videoscopes
• Today, many videoscopes can achieve 1000 µW/cm2 at around an inch
• One inch is an acceptable RVI distance
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

35. • “Black lights shall meet the requirements of 7.8.5.1.”
• Paragraph 7.8.5.1:
• “Blacklights, portable, handheld, permanently mounted, or fixed, which are
used to inspect parts, shall be checked for output at the frequency
specified in Table 1 and after bulb replacement. […] Minimum acceptable
intensity is 1000 µW/cm2 (10 W/m2) at 15 in. (38.1 cm) from the front of
the filter to the face of the sensor.”
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

36. • No industrial videoscope can project such UV power at 15 inches
• However, this is not a concern for RVI
• The first section “portable, handheld, permanently mounted, or fixed” limits the
scope of the standard
• It does not reference videoscopes
• For UV power on RVI, the ASTM E3022 standard needs to be referenced
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

37. • ASTM E3022 — “Standard Practice for Measurement of Emission
Characteristics and Requirements for LED UV-A Lamps Used in Fluorescent
Penetrant and Magnetic Particle Testing.”
• It lists the types of UV light sources and how they are to be measured
• Many different types are referenced
• In section 1 “Scope,” paragraph 1.3:
• “[T]his practice is only applicable for UV-A LED lamps used in the
examination process. This practice is not applicable to mercury vapor,
gas-discharge, arc, or luminescent (fluorescent) lamps or light guides
(for example, borescope light source).”
• RVI is not under the purview of calibration standards
Fluorescent Dye Penetrant Standards as They Apply to Videoscope Inspections

38. Summary and Conclusion

39. • FPI is a well-established method of visually inspecting small cracks
• Most of the history of FPI involves an inspector using a large, handheld UV light
source and directly visually observing any cracks several inches away
• Videoscopes now have UV LEDs of sufficient intensity to supplement common
FPI
• There are many stringent standards for FPI
• Videoscopes being used for FPI meet some of these standards
Summary and Conclusion

40. • Many, if not most, UV lights in RVI meet E1417 Paragraph 6.6.1
• “the ambient visible light background shall not exceed 2fc (20 lux) at the examination
surface. The black lights shall provide a minimum of 1000 µW/cm2 at the examination
surface”
• No UV light in RVI (that I know of) meets E1417 Paragraph 7.8.5.1:
• “Blacklights, portable, handheld, permanently mounted, or fixed, which are used to
inspect parts, shall be checked for output at the frequency specified in Table 1 and
after bulb replacement. […] Minimum acceptable intensity is 1000 µW/cm2 (10 W/m2)
at 15 in.”
• “That I know of”
• This technology is still new and rapidly improving
• Still would be very surprised at this intensity
• No current ASTM standard for these videoscope UV light sources
• We have seen some customers develop their own standards
Summary and Conclusion

41. Thank You