What is Radiation

What is Radiation :

X and Gamma Rays are a family of waves that are called electromagnetic waves. X-rays and gamma rays differ only in their source of origin.  X-rays are produced by an x-ray generator and gamma radiation is the product of radioactive atoms.  They are both part of the electromagnetic spectrum. They are wave forms, as are light rays, microwaves, and radio waves. X-rays and gamma rays cannot been seen, felt, or heard. They possess no charge and no mass and, therefore, are not influenced by electrical and magnetic fields and will generally travel in straight lines. However, they can be diffracted (bent) in a manner similar to light.

Introduction of the Magnetic Field

The required magnetic field can be introduced into a component in a number of different ways.

1.Using a permanent magnet or an electromagnet that contacts the test piece

2.Flowing an electrical current through the specimen

3.Flowing an electrical current through a coil of wire around the part or through a central conductor running near the part.

Magnetic Particle Testing

  • When a ferromagnetic material is magnetised the flux lines flow inside the component

  • When there is a discontinuity in the material there is flux leakage

  • The leaking flux attracts a magnetic medium resulting in an indication.

Post Emulsifiable Penetration System

Post emulsifiable Penetration System:

Post emulsifiable lipophilic/ hydrophilic   methods  are  formulated  to  maximize   penetrating  and  visibility characteristics.    They  do  not  contain  any  emulsifying  agent in penetrant   and  cannot  be  completely  removed  with  plain  water.

Post emulsifiable lipophilic: Removal  is  made  possible  by  applying  an  emulsifier  in  a  separate  process  step after dwell time for penetrant.    This  converts  the  excess  surface penetrant into an water washable penetrant . This emulsifier uses diffusion method to convert penetrant in to water washable.

Post Emulsifiable Hydrophilic Method: The  hydrophilic postemulsifiable, method also uses penetrants requiring a separate emulsifier.  The penetrants are the same  as  those  used  in  the  lipophilic  method.    The  difference  between  hydrophilic  and  lipophilic  methods  is  in  the emulsifiers.    Hydrophilic  emulsifiers  are  water  soluble  emulsifiers  and  actually  remove  excess  surface  penetrant  by means of a scrubbing  action rather than diffusion action.

Water washable Penetration method

Water-Washable, is the most economical method & it has not replaceable for rough casting surface, threaded & key surfaces.


  1.  Water-washable or self-emulsifiable penetrants contain an emulsifier as an integral part of the formulation.
  2. The excess penetrant is  removed from the object surface with a simple water rinse.
  3. Penetrant materials have the property of forming relatively viscous gels upon contact with water, which results in the formation of gel-like plugs in surface openings.
  4. While they are completely soluble in water, given enough contact time, the plugs offer a brief period of protection against rapid wash removal. Thus, water-washable penetrant systems provide ease of use and a high level of sensitivity.

Step in Solvent removable method.

5. Inspection:

Inspection  with visible dye penetrant  with minimum whate light intensity 100 foot-candles or 1100 lux  shall follow. Ultraviolet (UV-A) radiation of minimum intensity 1,000 micro-watts per centimeter squared is common, along with low ambient light levels (less than 2 foot-candles) for fluorescent penetrant examinations. Inspection of the test surface should take place after 10- to 30-minute development time, and is dependent on the penetrant and developer used. This time delay allows the blotting action to occur. The inspector may observe the sample for indication formation when using visible dye. It is also good practice to observe indications as they form because the characteristics of the bleed out are a significant part of interpretation characterization of flaws.

6. Post Cleaning:

The test surface is often cleaned after inspection and recording of defects, especially if post-inspection coating processes are recommended as per PT procedure.

Penetrant test method

Penetrant Classification System
Penetrants Type:
Type 1 Fluorescent Dye
Type 2 Visible (Red) Dye

Removal Method:
Method A Water Washable
Method B Post Emulsifiable, lipophilic (oil base)
Method C Solvent
Method D Post Emulsifiable, hydrophilic (water base)

Class 1 Halogenated (non-flammable)
Class 2 Nonhalogenated (flammable)
Class 3 Special Application

Developers Form:
Form a Dry Powder
Form b Water Soluble
Form c Water Suspendable
Form d Nonaqueous Type 1 Fluorescent (solvent based)
Form e Nonaqueous Type 2 Visible (solvent based)
Form f Special Application
Fluorescent Sensitivity*
Level 1/2 Ultra Low
Level 1 Low
Level 2 Medium
Level 3 High
Level 4 Ultra High