Concrete Coating Pipe

Radiographic testing

Radiographic testing is performed by recording degrees of absorption of penetrating radiation throughout the pipe wall. This results in generating a latent image of the object being under consideration or examined on a film that is later on chemically treated to transform the latent image into a permanent shadow image of internal and external defects in the pipeline. High intensity of radiation passes through the defected area when compared to regions without defects. Finally, these radiographer images can be evaluated by either professionals or automated computer vision systems.

Low-frequency electromagnetic testing (LFET)

In this process, the inspection process is accomplished by placing two ends of the electromagnetic driver on the metal surface, and a sensor is placed in between the two ends of the driver. The driver is a source of emitting low frequency (3-40Hz) alternating current signal and the sensors detect the magnetic field develops between the two poles of the driver. The principle of this testing is, “flaws in the steel structure alter the magnetic field”, this alteration is recorded by the sensors in the form of amplitudes and variation in phase. If more flaws are found, the deviation in the magnetic signal will become wider and the sensors will record more shifts in the magnetic signal. Finally, the recorded signals transformed into a percentage of material loss by using numerical calculations.

Balanced field electromagnetic testing

This process the inspection of cylindrical storage tanks can be consummated by placing an electromagnetic probe near a metallic body. The divergence in the magnetic field is recorded; the vertical and horizontal sections of the signal are phase-shifted to reduce the noise in determining the magnetic field.

Longitudinal ultrasonic testing

In ultrasonic testing, a transducer emits high-frequency ultrasonic waves and propagates them across the material under investigation. Further, the transducers record the time lapse between the waves released and when the waves’ echoes are received back to the transducers. In case of any flaws the time duration between the released and echoed waves condensed (comparing the absence of any flaws in the material). In ultrasonic testing, the particles in the material under consideration oscillate in response to the energy present in the ultrasonic waves propagated through it. The direction of the oscillation of particles is in the longitudinal direction.

Shear wave ultrasonic testing

The working principle of shear wave ultrasonic testing is the same to that of longitudinal ultrasonic testing. The only difference is the movement of particles is perpendicular to the direction of sound/ultrasonic waves. SWUT is also called angle beam testing, as it is employed to find out the flaws’ dimensions and their depth in the material under consideration.