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Pipelines are susceptible to different kinds of damage from internal and external corrosion, cracking, manufacturing flaws and other third party damage. The leakage of contents into the pipelines could be harmful to the environment, especially if the pipes are carrying gas or chemicals1.
Therefore, there is a need for the millions of miles of pipelines that run across the United States underground and above the ground that carry everything from water to crude oil to be inspected periodically for any signs of damage to prevent any environmental disasters1.
This inspection of pipelines could range from visual inspection to non-destructive testing. Non-destructive testing (NDT) includes a variety of analysis techniques to assess the properties of the materials without causing any damage to the material in the process1. Some of the tools used in performing NDT of pipelines utilize X-rays, magnetic particles and ultrasonic sound waves1.
While visual inspections or use of X-rays can be used to inspect pipelines above the ground, pipelines that are buried under ground or are hard to access require the use of devices known as “pigs” to perform the inspections1.
Available in various sizes, pigs have about the same diameter as the inside of the pipeline and are carried out by the flow of air or liquid. These devices are put into one of the pipelines and allowed to travel towards the other end of the pipeline to record valuable data that will be transmitted for further analysis of any flaws in the pipeline1. These pigs have the potential to travel several hundred kilometers in a single run1.
Pigs that use the magnetic flux leakage method use a strong magnetic field that is established in pipelines by magnets, or by using an electrical current to detect damage1. The array of sensors housed in the pigs detect the magnetic flux leakage at the damaged areas and provide details about the area of damage, which can then be taken care of by the Engineers.
While most of the pigs use magnetic flux, some utilize ultrasound technology to detect damage present within the pipelines. Pigs that use ultrasound technology have an array of transducers that emit high frequency ultrasound perpendicular to the pipe wall and record the time interval between the reflected sound (echo) from the inner surface and the outer surface to calculate the wall thickness, thereby identifying areas of damage in the pipeline1.
Companies such as Baker testing services and TELEDYNE ICM provide various NDT services for petroleum, gas and other pipelines. Baker testing services carries out a variety of NDT testing including Ultrasound Thickness Testing (UTT), Ultrasound-Phased Array (PA UT), Ultrasound-Time of Flight Diffraction (TOFD), Ultrasound shearwave, Radiography (RT, X-ray), Magnetic particles (MT, MPI), Liquid penetrant (PT, FPI, LPI), etc2. Phased Array ultrasound testing (PA UT) is used to identify geometry, anomalies and flaws in the pipelines using highly accurate images created by combining ultrasound waves produced by high speed electronics and composite multi element array probes2.
Magnetic particle testing could be used to test carbon steel and other ferromagnetic pipelines for surface cracks and other flaws2.
Remote visual inspection equipment is also used in some pipelines to inspect their condition1. Robotic crawlers of various shapes and sizes have been developed to navigate across the pipe by an operator in the control room1,3. The video signal from the crawler is usually fed by a truck where an operator can review the images and navigate the robot1. TELEDYNE ICM is the first portable X-ray Manufacturer to develop a dedicated generator for crawler inspections.3
These battery-powered, remotely controlled crawlers carry a panoramic generator into the pipe, thereby producing a single image that radiographs the entire weld in a single shot, which plays an important role in helping Engineers locate the area of concern easily. ICM recently launched two new constant potential generators for crawlers, CP160CR and CP180CR, that can fit into a 6” pipe, and are lighter, more powerful, energy efficient, while also allowing a duty cycle of 100%3.
Thanks to current technology, a variety of such NDT testing tools help us collect valuable information and locate the flaws in the pipelines thereby preventing leakages in pipelines that could be catastrophic.
Image Credit:
Kodda/ Shutterstock.com
References:
- “Pipeline Inspection” – NDT Resource Center
- “Independent Inspection” – Baker Testing Services
- “Pipeline Inspection” – Teledyne ICM
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