Non-destructive Examination, also known as non-destructive testing, includes methods to test or evaluate the structural condition or defects of a container without damaging it. Worldwide inspection services companies make use of several NDE methods to analyze welding defects or other structural or system damage caused to tanks, containers, or water towers.
Here, we have listed some of the widely used methods to conduct Non-destructive Examination.
- Acoustic Emission Testing (AE)
Acoustic Emission Testing is a passive testing technique. In this method, the API inspection companies look for short bursts of ultrasound that are emitted by cracks under the loads. The sensors are disseminated over the surface of the containers to check for acoustic emission. In highly stressed areas, one can detect AE from plasticization. The AE testing is used while conducting proof tests of a pressure vessel or structural health monitoring for bridges.
- Electromagnetic Testing (ET)
As the name suggests, in Electromagnetic testing, an electric current is passed through a conductor. The ET consists of three types; they are, eddy current testing, remote field testing, and alternating current field measurement.
- Ground Penetrating Radar (GPR)
Ground Penetration Radar is a geophysical method of NDE. In this testing technique, radar pulses are sent through the surface of the container or the structure. When the radar hits or encounters an object of different electromagnetic characteristics, the waves reflect or refracted.
- Laser Testing Methods (LM)
Laser testing consists of three types of techniques, which are laser shearography, laser profilometry, and holographic testing.
In the laser shearography technique, the laser light is used to create before and after images of a stressed surface. Both models are compared to detect any deviation.
In laser profilometry, a high speed rotating laser light source and a miniature optics are used to analyze erosion and cracks, pitting, or corrosion. The faults are detected by tracking the changes in the surface of the container via a 3D image produced from the above.
In holographic testing, laser light is used to detect changes in the surface of the container that has been stressed due to pressure, heat, or vibration. The finding is compared with samples of the undamaged surface.
- Leak Testing (LT)
Leak testing is divided into four methods. They are pressure change testing, bubble leak testing, mass spectrometer testing, and halogen diode testing.
The pressure change testing technique is only used to detect faults in closed systems. The testing is done either through pressure or vacuum to monitor the testing tank. If there is a leak in the tank or system, the loss of pressure over a set time will indicate it.
In bubble leak testing, a soap solution or liquid tank is used to detect air or gas leakage from the pipes. If there is any air leakage happening, bubbles will form around it.
In mass spectrometer testing, the leak is detected using helium gas and a sniffer.
Like the pressure testing method, halogen diode also used pressure to detect leaks. However, in this particular method, a mixture of air and halogen-based tracer gas, and halogen diode detection unit or sniffer is used to find out the leakage.