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Liquid Penetrant FAQ
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These specifications are presented in good faith researching information from various sources.   However, no guarantee or warranty is given to the accuracy of the above information.   You are advised to verify the correctness of these specifications prior to using them.  Use of these specifications assumes agreement with the disclaimer below. They are provided as a convenience to fellow enthusiasts and the author makes no expressed warranty to their accuracy, use at your own risk.

    Generally an oil base chemical solution of dye, either visible or fluorescent, capable of migration in surface openings by capillary action used to locate cracks in ferrous or non-ferrous materials, as well as some ceramics and plastics.

What is "capillary action"?

    The tendency of certain liquids to travel or climb into surface openings.
What is Liquid Penetrant Inspection (PT)?
    A nondestructive test method which provides for the detection of surface discontinuities (flaws) in ferrous and non-ferrous test materials.
What are the process steps for liquid penetrant inspection?
  1. Preclean & Dry
  2. Penetrant application (dipping, spraying, brushing)
  3. Penetrant removal (determined by the penetrant method usedówater washable, post emulsified, solvent removable)
  4. Drying
  5. Developer application
  6. Inspection
  7. Post clean
What are the advantages to liquid penetrant inspection?
  1. May be applied to a wide variety of test materials
  2. Simple to use
  3. Has a high sensitivity to very fine or tight surface discontinuities
  4. Indications appear on the actual test part
  5. Readily adapted to high volume production line inspection
  6. PT is a normally fast method of inspection which can be relatively inexpensive to use
What are the limitations of liquid penetrant inspection?
  1. Can only detect surface discontinuities
  2. Test materials should be nonporous
  3. Parts must be free from contaminants and coatings which could block penetrant travel
  4. Some penetrant materials may adversely affect plastic and rubber components
What are the liquid penetrant classifications?
    According to AMS 2644:
    TYPE 1 - Fluorescent
    TYPE 2 - Visible
    METHOD A - Water Washable
    METHOD B - Lipophilic Post Emulsified (oil based)
    METHOD C - Solvent removable
    METHOD D - Hydrophilic Post Emulsified (water based)
What is the recommended dwell time for your penetrant?
    Generally 5-15 minutes minimum (more sensitive applications require more dwell time)
Are there different developer application methods?
    Yes, the methods are:
    1. Wet nonaqueous (usually applied by aerosol spraying)
    2. Dry powder (applied by dipping, spraying/dusting, brushing) and Wet aqueous soluble (applied by dipping, spraying/flowing)
    3. Wet aqueous suspended particle (applied by dipping, spraying/flowing)


Last modified: April 26, 2005

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