Liquid Penetrant Testing & Inspection
Liquid penetrant (PT), also called Dye Penetrant, is an inexpensive non-destructive testing technique which can be easily performed by a certified inspector. Different NDT codes, specifications and procedures require the inspection to be performed in a particular manner. NDT inspectors performing Liquid penetrant (PT), should be certified to a Level 1, 2, or 3. Procedures such as SNT-TC-1A or NAS-410 are examples of the requirements NDT inspectors must follow.
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. Testing of high temperature applications such as hot-in-service pressurized pipes, must use a specially formulated penetrant chemical.
Liquid penetrant is often called FPI, Red dye, fluorescent check, black light check, and Magnaflux check. Magnaflux is actually a name brand known for specializing in both, liquid penetrant and magnetic particle which are two different testing methods. This unfortunately creates confusion on which method to use when a Liquid Penetrant test is referred to as a Magnaflux test.
Some basic things to consider when performing a liquid penetrant test are:
- Whether a visible or fluorescent penetrant is required
- The sensitivity requirements
- Whether pre-cleaning of the part or component is needed
- How accessible is the inspection area
- Is the dark room to be used capable of the 2fc lighting requirements