Advanced Ultrasonic Testing

Advanced Ultrasonic Testing

PHASED ARRAY ULTRASONIC TESTING (PAUT)

Principle.
Ultrasonic Phased Array is used to detect component failures such as cracks and flaws and can be applied for inspection of welds, thickness measurements, corrosion inspection and flaw detection.
Phased array ultrasonic systems utilize multi-element probes which are individually excited under electronic control. The PAUT probe consists of many small ultrasonic transducers, each of which can be pulsed independently and by exciting each element in a controlled manner, a focused beam of ultrasound can be generated.
The beam of ultrasound can be steered electronically and can be swept like a searchlight through the metal or object being examined. In this way two- and three-dimensional views can be generated showing the sizes and locations of any flaws detected in a "slice" view through the object.
Because the beam angle and focus can be controlled and manipulated, this method is very efficient in terms of speed and flaw detection.
Phased array provides; high speed electronic scanning without moving parts, improved inspection capabilities through software control of beam characteristics and inspection with multiple angles with a single electronically controlled probe.

Time of Flight Diffraction (TOFD)


Principle
TOFD inspection employs two longitudinal wave (L- wave) angle beam transducers arranged symmetrically opposite facing each other, dependable the weld or base material under test. One probe act like a transmitter of ultrasonic energy while the other probe receives the ultrasound energy. Time of Flight Diffraction is now routinely used in a wide range of applications such as inspection of piping and pressure vessels.


Long Range Ultrasonic Testing

Principle
Low frequency ultrasound is transmitted and received from a single location. The guided waves used travel long distances, even in entombed, submerged or insulated pipe, Response from flaws is a function of their depth and circumferential extent Focusing allows ultrasound energy to be concentrated into a small region of pipe for detailed localized inspection.

Application
Long Range Ultrasonic Testing is an advanced technology for detecting and analyzing corrosion where access is difficult.

Advantages

  • Low cost screening with 100% coverage
  • Focusing capability to evaluate corrosion distribution around pipe circumference Typical test range 60m from single location, ideal conditions can achieve longer distance.
  • Testing of pipes up to 48” diameter
  • Proven capability on pipe in service up to 125 Co
  • Detection of metal loss > 3%
  • Ideal where conventional testing is impossible or very costly

Short Range Ultrasonic testing (SRUT).


Short Range Ultrasonic testing also commonly known as SRUT is one of the Ultrasonic test methods where in the ultrasonic waves are transmitted in the form of pulsed guided laminar waves using special purpose ultrasonic probes. When laminar waves hit discontinuities, they are mode converted and the reflection of the waves are detected by the transducer.
Although Short Range Ultrasonic testing – SRUT is a screening technique used on wall thickness range of 6 to 25mm, this test method can locate the discontinuity location and size to an accuracy of ±10%. SRUT can detect discontinuities such as corrosion, pitting & erosion.

Internal Rotating Inspection System (IRIS Inspection)



IRIS is a technique that can be applied on both ferrous and non-ferrous materials and even on non-conductive materials like plastics. With IRIS the remaining wall thickness of tubes can be accurately measured. IRIS inspection is more accurate than other tube inspection techniques and has the advantages of presenting information about the geometry of defects. Local defects and wall-loss on both sides of the tube can be accurately measured. Defects under support plates can be measured without any limitations. 


The probe used in IRIS examination is made up of a centring device, an ultrasound transducer and a rotating mirror. Knowing the sound velocity in the material under test enables accompanying wall thickness to be calculated. Water is then used to rotate the probe mirror and is also needed as a couplant between the transducer and the tube wall. A calibration standard of the same material and dimensions as the tubes to be examined is used to check the IRIS system response in preparation for the inspection and the tubes should be cleaned to an acceptable standard.