Pipeline Inspection Using Non-destructive Testing Methods


Pipelines are susceptible to many different types of damage resulting from manufacturing flaws, cracking, internal and external corrosion, etc. There are millions of miles of pipelines that run across the nation, carrying water, industrial chemicals, crude oil, gas, and much more. Naturally, any leakage or other structural damage to these pipelines can have disastrous consequences. This is where non-destructive testing of pipelines comes in.

Non-destructive testing (NDT) refers to a series of testing and analysis techniques for the purpose of testing, inspecting, or evaluating materials, assemblies or components for differences in characteristics or discontinuities. Most importantly, these methods cause no harm to the serviceability of the system or part. Tools used for non-destructive pipe testing often utilise ultrasonic sound waves, magnetic particles, x-rays, etc. Compared to destructive tests, NDT is more preferred simply because they do not damage the equipment being tested.

Discussed below are some of the most commonly used non-destructive tests for pipeline inspection.

  • Dye Penetration Inspection or DPI: Also known as Penetrant Testing (PT) or Liquid Penetrant Inspection (LPI), this is the simplest and oldest of all NDT methods. This NDT technique is used for the detection of surface-connected discontinuities such as fractures, cracks, porosity, joint flaws, and incomplete fusion. This method operates around the principles of capillary action, and involves the penetration of low surface tension fluid into surface-breaking discontinuities.
  • Magnetic Particle Testing: Magnetic particle inspection or MPI or MT is used for the detection of linear flaws near ferromagnetic material surfaces. This method is particularly effective for locating surface-breaking defects such as pores, cracks, lack of sidewall fusion in welds, cold lap, etc in magnetic materials.  The most versatile MPI technique involves the use of a white strippable paint as the background, a hand-held electromagnetic yoke magnet, and a magnetic ink. MPI provides excellent defect resolution, and is extensively used in locating fatigue cracks in materials that are prone to cyclical stress.
  • Ultrasonic Testing: Ultrasonic non-destructive testing utilises high frequency sound waves to characterise the thickness or internal structure of the tested material. The pitch or frequencies used for ultrasonic testing are way beyond the limit of human hearing. This testing methodology has numerous industrial applications on plastics, ceramics, composites, and metals. As a result of the directional nature of high frequency sound waves, they tend to travel continuously through a medium until they encounter another medium’s boundary. When this happens, the waves are reflected back to reflect back to their source. Analysis of these reflections helps us find evidence of cracks and other internal faults or measure the thickness of the test piece.
  • Radiography Testing: X-rays and gamma-rays are used in radiographic testing to produce a radiograph displaying any defects, assembly details, and changes in thickness of a specimen. The working principle of this method is exactly the same as medical radiography used in different medical facilities. A permanent record is created by radiographic testing in the form of a radiograph, providing a highly sensitive image of a material’s internal structure. Although this method is expensive and relatively slower, it is a reliable technique for detecting cracks, inclusions, porosity, and voids in weld interiors.

At Austeck, we have been offering an exquisite range of advanced pipeline inspection and rehabilitation equipment since 1992. Please contact us to find out more about non-destructive testing and its benefits.