Every small sector are not affordable to have all type of NDT techniques in their own company. So they will approach to the near by company to make the result in quality. This is a cost us well us time consuming procedure. So some of the inspections other than LPT, RT, UT, MPT are carried out in their own limits by integrating some visual testing procedures. Small firms often uses some type of gauges, visually aided equipments, scales etc for visual testing to meet their demands within their limits.
Visual Testing is an evaluation of components by means of human sensory organs only by the aid of mechanical enhancement devices such as magnifiers, lenses, stethoscopes etc. The inspection process may be done using such behaviors as looking, listening, feeling, smelling, shaking, and twisting.
Importance among other NDT technique
All the other testing in NDT comes under Visual Testing. Not only in NDT, about the entire inspection, checking and analysis is done by visual inspection. The basic factor need to conduct an accurate visual Testing is inspector’s vision. Even Though the testing is carried out by other means like UT,LPT,MPT,RT, we use VT for the final validation of the result.
Requirements of VT
The requirements for visual testing:
- The inspector should have a proper vision.
- Amount of light falling on the specimen should be properly checked using a light meter and maintain accordingly.
- No obstruction of views should be their at the inspected area.
Note: Illumination and cleanliness of the specimen is an important factor that should be maintained during Testing.
Mchanical and Optical Aids Used in VT
Boroscopes are used to inspect the area where accessibility is difficult and expensive dismounting activities are involved.
- Magnifying glass
A magnifying glass is a convex lens that is used to produce a magnified view of an object.
Micrometer is used to measure the length or thickness of a material.
- UV Lights
Ultraviolet light makes fluorescent material to glow and is used in liquid penetrate and magnetic particle testing for detecting discontinuities.
Visual inspection of weld defects
The major defects that can inspected visually are Incomplete and excess Penetration, incomplete fusion, undercutting, slag and flux inclusion, porosity, spatter, sparks, lamellar tearing, overlapping, excess welding etc. All these defects can either identified by direct Visual Inspection or by other NDT techniques preceded by Visual inspection.