BIRNS Magnetic Particle Inspection-- Frequently Asked Questions
    What is “MPI”?
    What is “Black Light”?
    How does MPI work?
    Why is the UV filter necessary?
    How is Model 7701 packed?
    What are 'fluorescent particles'? Are they the same as "magnetic ink"?


  1. What is “MPI”?

    “MPI” stands for “Magnetic Particle Inspection”. MPI is the NDT (Non-Destructive Testing) technique of establishing a temporary magnetic field in the metal to be tested, to find cracks and weld defects.


  2. What is “Black Light”?

    “Black Light” is     UV (ultraviolet) electromagnetic radiant energy of 50-400nm wavelength. It's called “Black Light” because we can't see it. (By contrast, "White light" is radiant energy of 400-700nm wavelength, which we can see.)
  3. How does MPI work?

    The steps in MPI are:

    1. Magnetize the test metal.
    2. Apply fluorescent particles.
    3. Shine the BIRNS Blackbirn at the test metal.
    4. Record crack indications.

    Cracks interrupt the normal magnetic lines of force in the test metal; the UV-fluorescent particles make it possible to see that interruption.
  4. Why is the UV filter necessary?

    The BIRNS Blackbirn units emit both visible and UV energy. The UV filter is necessary to filter out the visible wavelengths; it permits the UV wavelengths to pass, but absorbs the visible wavelengths.

    The BIRNS Blackbirn UV filter only permits 360+/-30nm wavelengths to pass; the UV filter material is incorporated into the glass of the pressure port (tempered for added strength and domed for extra depth capacity). There are no inefficient and wasteful separate filters or 'baffle' support plates required.
  5. How is Model 7701 packed?

    The Model 7701 is packed and shipped in two packages.

    1. Model 7705 Lighthead and Model 7703 Articuleg are packed into the 13B-001 Case, then boxed in a 84 x 61 x 43 cm (33 x 24 x 17 inch) carton, weighing 35 Kg (76 lbs).

    2. Item 17F-036 cable (150m/500') is installed onto the 13C-002 Reel, then boxed in a 53 x 64 x 56 cm (21 x 25 x 22 inch) carton, weighing 60 Kg (132 lbs).

  6. What are 'fluorescent particles'? Are they the same as "magnetic ink"?

    'Fluorescent particles' are mixtures of iron particles and non-toxic fluorescent chemicals. BIRNS supplies these in powdered form, for use as "ink" for MPI, in two versions:

    "Pink" (fluoresces under both "White Light" and UV) and
    "Gold" (fluoresces only under UV).

    52C-003: 1-lb jar, Fluorescent particles (Pink)
    52C-005: 2-lb jar, Fluorescent particles (Pink)
    52C-004: 1-lb jar, Fluorescent particles (Gold)
    52C-005: 2-lb jar, Fluorescent particles (Gold)

    The "Pink" particles provide a bright fluorescence under visible light wavelengths, and turns 'hot pink' under UV...these are very popular.

    The "Gold" particles provide an amazing, brilliant fluorescence under UV light only (under visible light, these are a dull light-brown color) and thereby prevents visual interference by visible debris, etc. It's really obvious when you get an "indication"-- your clients will love it!