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In the mining industry, the reliability of mining equipment and the safety of personnel working with it is of paramount importance. Equipment can be placed under enormous strain due to the harsh working environments present in mines and quarries, such as highly variable rock types, which can lead to catastrophic failures, resulting in injury and potential death, as well as lost productivity and time for the mining project. Therefore, monitoring the equipment for damage and potential flaws is vital for the industry.
Non-destructive testing (NDT) is an umbrella term for a range of techniques that can be incredibly useful for testing the integrity and proper function of mining equipment. NDT methods can evaluate a material or component’s properties without causing undue damage or altering it, saving time and money.
NDT methods rely on the use of electromagnetic radiation, sound or other types of signal conversion to inspect the material in question. Multiple NDT methods exist which have been developed since the early 20th Century and have been utilized in several different industries, including medicine, art, electrical engineering, civil engineering, and systems engineering, in addition to the mining industry. NDT is one of the most widely-used analysis methods in modern scientific research and quality assurance, as it is particularly suited to a wide array of applications and industries.
The Needs of the Mining Industry
As has been mentioned, the mining industry faces several issues that can severely affect the profitability and sustainability of mining projects worldwide. As the equipment is integral to any ongoing project, regular testing is of central concern for project managers and companies. There are internationally agreed sets of regulations and standards that mining companies must adhere to.
Components that can fail and therefore need to be tested for flaws include wiring, hydraulic cylinders, drills, bearings, circulating pumps, and motors. As mining equipment can be complex, a seemingly small flaw in any one of these components can lead to a larger system-wide problem further down the line.
The same asset can even demonstrate different failure behavior in different environmental conditions. For example, an asset may appear fully functional in a highly silicified gold mine but not when compared to its function in a bituminous coal mine. Evaluation of the material used in the mining equipment’s components can lead to choices of suitable materials for the task in hand.
NDT Methods Suitable for the Needs of the Mining Industry
Mining brings its own set of particular needs, which can affect the suitability of NDT methods employed for the analysis of machinery. Two commonly used NDT methods and their application to mining equipment analysis and quality control are Magnetic Particle Testing and Ultrasonic Testing.
Magnetic Particle Testing (MPT)
Sometimes also referred to as Magnetic Particle Inspection (MPI) this process is used to detect surface cracks and anomalies in ferromagnetic materials and electrically conductive materials.
As the name suggests, the process uses a magnetic field to test for discontinuities near the surface of said materials. In this technique, the magnetic field can be induced either directly or indirectly, and any surface or subsurface discontinuities cause leakage in the magnetic flux, which can reveal their presence. After cleaning the subject component of impurities, ferrous particles, either dry or in suspension, are applied to the subject. These are attracted to an area of flux leakage. This forms what is known as an indication, which is then detected by specialized equipment and informs decisions on the quality of the material in question and whether it should be used or rejected.
Ultrasonic testing (UT)
Ultrasonic testing methods are some of the most widely used and indispensable methods in the mining industry.
The process uses short pulse-waves of ultrasonic (sound) energy to detect flaws and irregularities in equipment and materials. Sound waves travel at different velocities in different materials, and a change in velocity can be indicative of a flaw or discontinuity. Once this change in velocity detects a flaw, the sound waves are reflected back to the transducer, and by comparing them, the location of the flaw and its size can be determined.
UT has many benefits for the mining industry. These include:
- It can be used for analyzing complex and unique shaft geometries
- Minimizing downtime: UT is a fast method compared to other NDT techniques
- UT has a high probability of critical defect detection
- UT is a reliable and dependable method
Ability to penetrate internal structures: No disassembly needed of equipment such as pressure vessels and pipelines, which means that cost and time is significantly reduced
MPT and UT can be used in a complementary manner for testing a wide range of mining equipment and materials during development and operational phases. Other testing methods, including Visual and Optical Testing (VT), Penetrant Testing (PT), and Leak Testing (LT), can be utilized for different purposes due to their unique suitability for various tasks.
NDT is extremely valuable and can vastly improve the efficiency of mining projects. Even though these techniques require operators to be highly trained specialists, automated processes have been developed over the years, and databases have been utilized extensively to aid the process significantly. Knowledge of the materials and stress factors that are of particular interest to the mining industry that has been acquired through the application of NDT will serve the industry well as it faces new challenges in the future.
References and Further Reading
Ultrasonic testing – an essential NDT technique for the mining industry – Mining.com
Sutcliffe, D.A and Cottier, J.A (1978) Successful applications of NDT techniques to mining equipment maintenance NDT International Vol. 11 Issue 3. Pgs. 135-137
Everything You Need to Know About Non-Destructive Testing (NDT) – Nexxis.com.au