Liquid Penetrant Inspection:

This method is used to detect surface breaking discontinuities, which are free from  debris that can limit the entrance of the dye.  

This method is carried out on both ferromagnetic and non-ferromagnetic materials. But its commonly used in non-ferromagnetic materials in carrying out this method, the surface of internal is first cleaned and test area is applied with dye solution, either visible or florescent.  After a required dwell time the dye is removed and a thin coating of developer is sprayed over the test area. 

For florescent dyes, an ultraviolet lamp is needed to allow the indicator show well.


  • Magnetic Particle Inspection (MT)
  • Liquid Penetrant Inspection (LT)
  • Ultrasonic Testing (UT) – Wall Thickness Measurement (UTM) and
  • Flaw Detection
  • Eddy Current

Magnetic Particle Inspection:

This method is used to detect the presence of surface braking discontinuities (cracks).  It’s   carried out on ferromagnetic materials only. 

The application is done either dry or wet form.  The test is carried out with an AC Yoke or DC Yoke (magnet) with application of either florescent or contrast medium and black magnetic.

 Ultrasonic Testing (Wall Thickness Measurement & Flaw Detection)

This is an acceptable method for checking wall thickness of materials i.e. pipes and   plates. Commonly used for areas suspected to the corroded or where access is limited to the other side of the material. 

Also it is used to detect flaws in a material i.e. lamination in plating, cracks, welding defects, porosity, lack of fusion etc. It’s now a common method used as an alternative for Radiographic inspection.

Visual Inspection:

This method involves comprehensive visual examination according to training and standards.

Radiographic Inspection & Interpretation:

This method involves the use of X-rays or gamma rays to produce image of an object on film.  On passing an X-ray source on a side of a specimen and photographic film at the other side, an image is obtained on the film of the thickness variations in the specimen, whether surface or internal.    This technique is widely used to detect internal flaws in weldments and castings, also to check for mis-constructions in assemblies.