Ndt visual inspection

Non destructive test and types

1. Visual Inspection (NDT) B y - P A W A N K U M A R P G W L F 2 1 5 5 6

2. Visual Inspection (NDT) Visual Inspection of Weld Joints Visual examination of weld joint is an important activity, carried out to check the integrity and soundness of the weldment . It is an economical activity, as it doesn’t require any costly equipment. It must be carried out by a well experienced inspector. Main responsibilities of a welding inspector are : Code compliance Workmanship control Documentation Control

3. R equirements for visual examination The requirements of visual examination are : Illumination should be at least 350 Lux (minimum) but it is recommended to carry out visual inspection at an illumination of more than 500 Lux . The inspectors eye should be within the radii of 600 mm of the surface of item being inspected and the viewing angle must not be less than 30 degrees . Welding gauges, m agnifying glasses and boroscope or fibre optic viewing system (when access is restricted ) can also be used.

4. Requirements for visual examination Figure 1 – A typical direct view borescope

5. S tages of visual inspection Before Welding:  The inspector shall be familiarized with the applicable codes and standards /drawings /welding procedures (WPS and PQR). Welder qualification shall be carried out before production welding. The inspector shall confirm the material and welding consumables before welding .  Joint preparation and alignment shall also to be checked prior to welding. After confirmation of all the parameters , the welding inspector can permit the welder to start the production welding. If preheat is applicable, then the preheat temperature shall be confirmed before starting the weld.

6. Stages of visual inspection During Welding:  The inspector shall check the welding process and welding parameters with respect to the welding procedure specification (WPS) at any time during welding. Root run and root run dressing, inter pass temperature shall be witnessed by the inspector.

7. Stages of visual inspection After welding:  After complete welding, identification number is punched near joint. Complete visual inspection is done and any surface breaking or defect shall be repaired as per approved procedure. Following defects (or discontinuity) can be revealed by visual inspection: Crack Underfill Undercut Surface porosity Overlap Lack of side wall fusion Arc strike Spatters Excessive Penetration Unacceptable weld profiles

8. Advantages of V isual I nspection Inexpensive (usually only labor expense) Low cost equipment No power requirement Quick identification of defects and downstream repair costs due to issues that weren’t caught early

9. Disadvantages of Visual Inspection Inspector training, knowledge and skills are necessary Good eyesight required Can miss internal defects Report must be recorded by inspector Possibility of human error