What are some widely used Methods of Non-destructive Tank Inspection?

Storage tanks and containers are widely used across various industries. Since storage tanks play a crucial role in keeping the stored product away from contamination, one must ensure the tanks are functioning optimally. There are different tank testing methods used by professionals from API inspection companies.
Non-destructive testing or NDT is a commonly used technique to inspect the tanks’ structural condition and detect any signs of contamination. In the NDT method, the tank and its components are inspected without causing damage to the tank. One can use the NDT method to look for structural damage, corrosion, leakage, blockage, or contamination.

In this blog, we will look into some commonly used.
1. Acoustic Emission Testing (AE)
Acoustic Emission, or AE, is a type of passive non-destruction testing method used to look for defects in a tank. The tank inspectors from API inspection services companies look for signs of short ultrasound bursts that are caused due to cracks in the tank. The sensors are placed on the surface of the tanks. Inspectors can detect areas with high-stress points through plasticization.
2. Electromagnetic Testing (ET)
In electromagnetic tank testing, an electric current is passed through conductors. Eddy current testing, remote field testing, and alternating current field measurements are common types of electromagnetic testing.
3. Ground Penetrating Radar (GPR)
Ground-penetrating radar or GPR is a type of geophysical testing method. Radar pulses are sent across the surface of the tank to detect any damage or defects. In case of any abnormalities in the tank or its content, the radar waves refract or reflect. This allows one to identify where the leakage or contamination is present.
4. Laser Testing Methods (LM)
There are three types of laser testing. They are laser shearography, laser profilometry, and holographic testing.
Laser Shearography Testing: In this particular type of laser testing, laser light is used to create the stressed surface images. One can capture the before and after pictures of the tank surface and use them to study the tank’s condition. Any defect or deviation in the tank surface can be easily identified through shearography.
Laser Profilometry Testing: In this test, a rapidly rotating laser light source and small optics are used to look for corrosion, cracks, or leakage. The 3D image produced via the apparatus allows one to identify changes in the tank surface.
Holographic Testing: Holographic testing is done on the stressed tank surface. The test allows one to detect any changes resulting from pressure, vibration, or heat.
5. Leak Testing (LT)
Pressure change testing, bubble leak testing, mass spectrometer testing, and halogen diode testing are some commonly used leak testing methods.
In the Pressure Change Testing method, closed tank systems are inspected to detect any possible leakage or faults. Pressure or vacuum are used to test the tanks. In case of any leakage present in the tank, the loss of pressure will indicate it.
Bubble leak testing is conducted with the help of a soap solution. The bubble leakage testing method is used to detect any sign of leakage in gas lines or tanks. Upon applying the soap solution on the tank surface or pipeline, air bubbles will appear around it, indicating any leakage.
In halogen diode testing, the pressure is used to inspect the tanks. To conduct halogen diode test, air mixture, halogen-based tracer gas, and sniffer are used.