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What is NDT?

NDT is a single Dimensional measurement.

What is the purpose of doing NDT?

For any material products the premature failures are due to corrosion, erosion and fatigue failure. In all these process material eating away will takes place that results in reduction of material thickness finally premature failure will occur in addition to that failure in load carrying capacity. Mostly the shape of defects are linear in nature. Linear type are having sharp edges and they acts has a "stress riser" upon the pressure and tend to propagate. That's why linear defects are detrimental to the product than rounded defects.

So, finally in all NDT methods we measure the length of the defects only.

Expansion of Single Dimensional "measurement"

For any measurement, two basic components are very essential.

  • Person to measure
  • Equipment to measure

The document that deals with the measuring persons, here the NDT personnel is termed as written practice and administration of NDT personnel.

Then, the document that deals with the measurement equipment is written procedure.

Qualifying NDT personnel

There are basically two types of NDT personnel qualification

  • Company requirement based on SNT-TC-IA.
  • Specific requirement based on CP-189.

ASNT's SNT-TC-IA is serving as a guide to prepare a written practice. According to SNT-TC-IA, the NDT personnels are qualified based on.

Physical Examination Comprises
  • Vision Acuity
  • Near Vision (Jaeger Chart)
  • Color Vision (Ishihara Chart)
  • 18% gray chart

A person capable of reading J1 letter size of 1.5mm height at a distance 12 inch with corrected or uncorrected at least one eye enable to detect 2mm defect size. As per SNT-TC-IA NDT personnel qualification comprises in two parts.

Written Examination Comprises
  • General 40 Questions
  • Specific 20 Questions
  • Practical 10 Questions
There are three levels of qualification.
  • NDT Level I
  • NTT Level II
  • NDT Level III
Duties of NDT Level I, II, III – in short
  • Level I records the test results.
  • Level II Set up and Calibrate the equipment and report preparation.
  • Level III qualifies Level I of Level II.

Overall NDT Methods are categorized into Basic NDT and advanced NDT Methods. Also, they are classified into surface NDT Methods (test result found on the test surface itself) and subsurface NDT Methods (needs seperate recording medium).

Five Building Blocks of NDT
  1. Basic Principle
  2. Artificial Defect
  3. Probing Media
  4. Testing Media
  5. Recording Media

NDT defects are expected defects. One from the known artificial defect(s) to defect unknown natural defects in the part under test.

Again defects are categorized into rounded indication ( Length is less than 3 times width) and linear indication ( Length is greater than 3 time Width).

Test Parts and Documents

The overall NDT Methods rely on two things -the test part ( Interpretation) and the document ( Evaluation). Interpretation determine the cause and nature of defects and Evaluation is determine the Severiety of defects. Test results from the test parts have been compared with the documented acceptable standard. Deviation of test results with the observed test results cause for rejection.

We, the SQS Institute of NDT regularly conducting NDT Level I of II training and certification programme in MT, PT, RT, UT and VT both it in – house and at customer premises.

Over 5000 persons have been effectively trained and certified by SQS Institute of NDT in the past two decades.

NDT Level III conslutant and Preparatory classes also carried out regularly in MT, PT, RT, UT and VT.

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