Liquid Penetrant Testing & Inspection

Liquid penetrant (PT) also called dye penetrant is an inexpensive Nondestructive testing technique which can be easily performed by qualified certified inspectors. Different NDT Codes, Specifications and Procedures require the inspection to be performed in a particular manner. Each has their own particular requirements to be followed.Depending on the critical nature of the part, an inspector performing Liquid penetrant (PT) should be qualified and certified to a Level 1,2, or 3 per an NDT qualification and certification procedure such as SNT-TC-1A or NAS-410.

Liquid Penetrant PT services are most often used to detect cracks and voids open to the surface of nonporous metallic materials. The sensitivity rating of penetrants allow them to be used on casting and machined surfaces by using lower sensitivity level ½ on castings and level III on machined surfaces. Specially formulated liquid penetrant chemicals may be used for high temp applications for the inspection of tubes and Hot in service pressurized pipe. Liquid Penetrant may be performed before and after Hot taps. Liquid penetrant is often called a Magnaflux check. Magnaflux is a name brand known for specializing in liquid penetrant and magnetic particle which could lead to a misunderstanding of the inspection actually required. Other common names are FPI, Red dye, fluorescent check, black light check or what is that that check they do under a black tarp with black lights. Basic things to consider when performing liquid penetrant are.

  1. Is visible or fluorescent penetrant being required
  2. What is the sensitivity requirement
  3. How clean is the part or component and is pre cleaning going to be required.
  4. How accessible is the inspection area
  5. Is the requirement to use Method A Water Washable, Method B Post Emulsifiable Lipophilic, Method C Solvent Removable, or Method D Post Emulsifiable Hydrophilic.
  6. Is there a dark room available to achieve the 2fc light requirement.
  7. Will power be available.