Visual Testing

Visual Testing

NDT process – nondestructive testing is the original term used to identify a method of inspection that does not destroy product usefulness. Current terms include nondestructive inspection (NDI) or nondestructive evaluation or examination (NDE)

Examination with the eye, therefore you are only able to detect surface discontinuities. Most important and most extensively used NDE/NDI/NDT method.

Visual Inspection or Visual Testing (VT) requires line-of- sight contact with the portion of the specimen to be inspected, adequate illumination of the test specimen, a thorough understanding of the nature and origin of discontinuities and potential defects within the test object, and familiarity with the specifications controlling theinspection process. Unless the specimen cannot be examined visually, visual testing should be the first part of any NDT examination.

Visual testing presents several real advantages: simplicity, rapidity, low cost, minimal training and equipment requirements, and the ability to be performed while the specimen is being used or processed.

Mechanical or optical aids may be necessary to perform visual testing. Before any mechanical or optical aids are used, the specimen should be well illuminated and its surface cleaned. Often the inspection locates areas where other NDT techniques need to be applied, or areas where the mechanical and optical aids may provide superior inspection. Often visual inspection eliminates the need for further testing and the associated costs. This method is used to inspect a variety of product forms including castings, forgings, machined components and weldments.

The structural steel, automotive, petrochemical, power generation, and aerospace industries are a few of the many types of end users utilizing visual.

The Level I and II visual testing course requires no prior training or experience by the student, and indeed could be a great foundational starting place for all inspectors. Training material is presented in a manner that promotes understanding and the ability to make immediate application. Basic courses are ideal for NDT trainees who must have Level I and II training in order to qualify for certification as well as facility personnel who are responsible for or oversee the application of testing or Quality Control/Quality Assurance.

Visual inspection is a non-destructive testing (NDT) weld quality testing process where a weld is examined with the eye to determine surface discontinuities. It is the most common method of weld quality testing.

Visual testing can be classified as :

  • Direct visual testing
  • Remote visual testing
  • Translucent visual testing.

The most common NDT methods MT and PT are indeed simply scientific ways of enhancing the indication to make it more visible.

Visual Weld Equipment :

  • Fillet Weld Gauge
  • Magnifying glasses
  • Microscopes (optical and electron)
  • Optical comparators
  • Mirror on stem
  • Illuminated magnifier
  • Inspection glass,
  • Bore scope

Visual Weld Quality Testing Steps :

  • Practice and develop procedures for consistent application of approach
  • Inspect materials before welding
  • Weld quality testing when welding
  • Inspection when weld is complete
  • Mark problems and repair the weld
Visual Weld Equipment

Advantages of nondestructive weld quality testing :

  • 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

Disadvantages :

  • Inspector training necessary
  • Good eyesight required or eyesight corrected to 20/40
  • Can miss internal defects
  • Report must be recorded by inspector
  • Open to human error

The applications of visual testing include:

  • Checking of the surface condition of the test specimen.
  • Checking of alignment of mating surfaces.
  • Checking of shape of the component.
  • Checking for evidence of leaking.
  • Checking for internal side defects.

Responsibilities of ASNT Level II Visual Testing (VT) Personnel

  • A certified ASNT Level II Visual Testing (VT) personnel is qualified to identify various weld discontinuities.
  • A certified ASNT Level II Visual Testing (VT) personnel is qualified to understand the relevant welding Process related to visual inspection.
  • A certified ASNT Level II Visual Testing (VT) personnel is qualified to understand the need for documentation in welding.
  • A certified ASNT Level II Visual Testing (VT) personnel is qualified to carrying out the Visual Testing (VT) on parent materials and consumables.
  • A certified ASNT Level II Visual Testing (VT) personnel is qualified to perform Visual Testing (VT) of welds, report on them and assess their siviority with specified acceptance criteria.