Each non-destructive tests are unique assessment techniques that help an industrial asset restrict undue flaws that hamper the churning of machinery. It is also crucial that these tests are carried out precisely for accurate and unbiased results that cater to the industry’s betterment. For a successful NDT services, engineers should keep four integral concepts in mind.
Both the NDT services taker and service provider need to know the limitations and advantages of NDT methods. The NDT testing and techniques used to find flaws should be precisely selected. The common test methods are Visual Inspection, Ultrasonic Testing, Magnetic Particle Testing, Dye Penetration Testing and Radiography testing. The selection of test methods and techniques depends upon the purpose of inspection, finding discontinuity/ abnormality, or monitoring identified flaws. It is essential to select a specific NDT method before testing to get the best results.
To facilitate a better understanding, several examples can be quoted –
- Consider a Forged shaft: Before proceeding with the machining, NDT is more or less sine-qua-non to ensure freedom from defects. One can perform Ultrasonic testing using normal beam technique to detect any internal/planar or volumetric defects and Magnetic particle testing for surface defects like forging laps which would normally escape in normal beam ultrasonic testing. If any unacceptable flaw is observed, the raw material is rejected, and the processing cost can be saved.
- Once the raw material is satisfactory with respect to all the tests carried out, it can be processed. In the event of any heat treatment done, it becomes necessary to check for heat treatment cracks. At this stage, Ultrasonic will be seldom helpful, and Magnetic particle testing must be carried out to detect heat treatment cracks.
- Another example of the selection of technique when inspecting ferrous material during the in-service inspection, it is much necessary to anticipate a damage mechanism of the component. WFMPI (Wet fluorescent magnetic particle inspection) is the best option for damages like fatigue. Since fatigue is a surface phenomenon, WFMPI is the most sensitive technique (in comparison to PT and visible MPI) for detecting surface cracks in ferromagnetic materials.
A testing method should not be selected because it is new and advantageous. For instance, an inspection of tubes of coolers where the damages anticipated are pitting, erosion etc., from inside, techniques like IRIS and Eddy current are used, as well as APR. While the damages from OD are expected, APR would be the least helpful, and eddy current testing would be the best.
Perseverance of NDT personnel
Probability of detection of defect decreases as the quantum of testing increases. NDT personnel must be mentally and physically fit to carry out the testing. To refresh oneself, it is advised to carry out the testing intermittently and take a break for 5-10 minutes after every hour of testing.
The integrity of NDT personnel
Integrity is a part of the culture of the company providing NDT services. The Remuneration of NDT personnel should not be concomitant with the performance of an individual. For instance, the Remuneration of personnel should not be based on the number of samples tested, accepted or rejected.
Efforts made by NDT services taker
One needs to make the necessary efforts to get the best of NDT. Surface preparation is one of the major areas wherein the efforts of NDT service takers are involved. If the service provider is responsible for surface preparation, his energy will be wasted in preparing the surface required for NDT. Service takers should take the initiative in arranging for the best surface preparation and congenial environment for NDT to get the best results. Inspection time should be sufficient to complete the inspection.
Precautionary innuendoes –
In the first case cited in point 1, it will require proof machining on the forged samples before carrying out UT and MT. It will be required to remove scaling after shaft heat treatment before carrying MT. For the 2nd example cited in point 2, it is necessary to carry out buffing/grinding to remove any oxide scales before conducting WFMPI for in-service inspection.
TCR Advanced Engineering incorporates all these above qualities, leading it to be one of India’s Top NDT service providers in 2021. Increase the efficiency of your industrial assets and regale safer programs for prosperous industrial productivity with TCR Advanced – the Best asset integrity and optimizing services providers.