Evaluating Pipeline Inspection Technologies for Enhanced Corrosion Detection in Mining Water Transport Systems

Abstract

Water transport pipelines in the mining industry face significant corrosion challenges due to extreme environmental conditions, such as arid climates, temperature fluctuations, and abrasive soils. This study evaluates the effectiveness of three advanced inspection technologies—Guided Wave Ultrasonic Testing (GWUT), Metal Magnetic Memory (MMM), and In-Line Inspection (ILI)—in maintaining pipeline integrity under such conditions. A structured methodology combining diagnostic assessment, technology research, and comparative evaluation was applied, using key performance indicators like detection capability, operational impact, and feasibility. The results show that GWUT effectively identifies surface anomalies and wall thinning over long pipeline sections but faces depth and diameter limitations. MMM excels at detecting early-stage stress and corrosion in inaccessible locations, benefiting from minimal preparation and strong market availability. ILI provides comprehensive internal and external assessments but requires piggable pipelines and operational adjustments, limiting its use in certain systems. A case study of critical aqueducts of mining site water supply illustrates real-world technology selection challenges. The findings underscore the importance of an integrated inspection approach, leveraging the complementary strengths of these technologies to ensure reliable pipeline integrity management. Future research should focus on quantitative performance metrics and cost-effectiveness analyses to optimize inspection strategies for mining infrastructure.

1. Introduction

Water scarcity is a critical global issue, recognized by the World Economic Forum as one of the top three global risks [1,2,3]. Effective water resource management is essential to addressing this challenge. Pipelines play a crucial role in transporting essential resources, such as water, oil, and chemicals, especially in the mining sector [4,5,6]. Given the potential environmental and economic consequences of pipeline failures [3,7], maintaining pipeline integrity is crucial [8,9].

The mining industry presents particularly complex pipeline integrity challenges [5,8,10,11,12,13]. Mining pipelines transport water and other resources over vast distances through rugged terrain and are subject to a variety of stressors—abrasive particles, chemical interactions, high pressure, and environmental fluctuations. These factors accelerate corrosion and material degradation, increasing the risk of structural failure. Such failures can have severe environmental and operational consequences. Pipeline failures that contaminate water are particularly harmful, especially in mining operations where pipelines carry mine water potentially containing heavy metals, acidic compounds, or other hazardous substances. For example, Bebbington and Bury [13] highlight how failures in Peru’s mining infrastructure have caused significant water pollution, impacting ecosystems and communities dependent on clean water. Similarly, Hamilton [12] emphasizes that inadequate water management in mining can contaminate water bodies, posing long-term risks to both environmental sustainability and human health. Thus, ensuring the durability and reliability of these pipelines is critical for both sustainability and operational efficiency [12,13].

In Chile, a leading mining country with 13.6% to the national GDP [14] and 55.3% share of total exports in 2022 [15], pipelines are especially important due to the region’s arid conditions, where water resources are already limited. Although the mining industry accounts for only 3% of Chile’s water usage [16], most operations are situated in the driest regions, underscoring the need for sustainable water use and efficient pipeline management [17,18]. Consequently, robust pipeline integrity management strategies are essential for the industry, requiring reliable inspection and maintenance methods tailored to the mining sector’s challenging environments [6,19,20,21].

Traditional inspection techniques, such as visual inspections and radiography, are often inadequate for the demands of mining pipelines. Visual inspection, the most commonly used non-destructive testing (NDT) method due to its simplicity and cost-effectiveness, is clearly limited by its inability to detect internal or early-stage defects without supplementary methods [22]. Radiography, although more comprehensive, requires significant expertise, is costly, and may not detect all types of anomalies, especially in inaccessible locations [20]. These limitations emphasize the need for advanced, non-disruptive inspection technologies that can address the remote, large-scale, and rugged pipeline conditions of the mining sector [6,8,23].

To overcome these limitations, recent advancements in NDT offer more promising approaches for mining pipeline inspection, including Guided Wave (GW), Metal Magnetic Memory (MMM), and In-Line Inspection (ILI) technologies. Each of these methods has unique capabilities and limitations. Guided Wave (GW) technology uses ultrasonic waves that propagate along the pipeline to detect surface-level anomalies over moderate distances without the need for full pipeline access. This technology is especially useful for identifying corrosion and structural flaws in above-ground pipelines. However, GW is limited by signal attenuation over long distances, reducing its effectiveness in large pipeline networks typical in mining [24,25,26]. GW excels at long-range detection of large-scale structural defects like wall thinning, cracks, and weld anomalies, but its lower resolution limits its sensitivity to smaller, localized defects, such as pitting corrosion and micro-cracks [27]. Metal Magnetic Memory (MMM) detects early-stage stress and strain in ferromagnetic materials by identifying magnetic field distortions caused by structural anomalies. MMM is advantageous for inspecting buried pipelines and inaccessible locations but is restricted to ferromagnetic materials and is vulnerable to interference from external magnetic fields, which can be common in mining environments [28,29,30]. The maximum effective depth depends on factors such as the pipe’s material and diameter, the magnetometer’s sensitivity. Generally, MMM is most effective for shallowly buried pipelines (typically less than a few meters). Soil composition, moisture, and the presence of magnetic minerals can create background noise and distort the magnetic field, making it difficult to isolate signals from the pipeline. Magnetic field scattering at the interface between the pipe and the soil, as well as the presence of rocks or other nearby metallic debris, can also interfere with measurements.

In-Line Inspection (ILI), or “pigging”, involves devices that travel through pipelines, providing high-resolution data on internal corrosion, cracks, and deformations. ILI offers comprehensive data [31] and requires pipelines to be compatible with pigging devices, which can limit its use in pipelines with non-standard structures [8]. ILI may also require temporary flow adjustments [23,32,33], while modern ILI systems equipped with speed control units can operate without significant disruption to pipeline operations.

Current advances in ILI pipeline inspection and corrosion detection technologies highlighting diverse non-destructive testing (NDT) methods and multi-sensor systems tailored for complex infrastructure. The work by Guan et al. [23] reviews intelligent pipeline inspection gauges (PIGs) that utilize sensor fusion technologies, including micro-inertial measurement units (MIMUs), to improve the accuracy and efficiency of pipeline surveying. This approach integrates multiple sensors for a comprehensive assessment of pipeline integrity, which is critical for detecting and localizing defects in buried pipelines that are often missed by conventional methods.

Novel nondestructive techniques, such as remote field eddy current [34], ground-penetrating radar [7,9], and advanced acoustic emission methods [20], offer significant advantages for pipeline health monitoring and corrosion detection. These technologies, as demonstrated by recent studies, enable high-accuracy defect identification and real-time pipeline condition assessments, particularly in environments where traditional methods fall short due to accessibility constraints [20,34]. Prediction capabilities in multi-regional water networks demonstrated importance of integrating machine learning with conventional inspection methods to address complex and large-scale pipeline systems effectively [6,35,36].

Furthermore, knowledge graphs and neural networks have demonstrated efficacy in predicting corrosion rates within oil and gas pipelines [37]. A review by Azmi et al. [38] underscores the importance of accurate predictive analytics within the oil and gas sector, highlighting the application of machine learning for this purpose. This review provides an overview of recent research, detailing various methodologies, their advantages, and disadvantages, while also suggesting future research directions to enhance predictive analytics in the sector. However, the current literature offers limited guidance on technology selection for water systems, particularly within the mining industry.

Although each pipeline inspection technology offers distinct advantages, selecting the most appropriate method for the diverse challenges of mining environments remains a complex task. Guided Wave technology faces limitations over long distances, Metal Magnetic Memory is restricted to ferromagnetic materials and susceptible to magnetic interference, and In-Line Inspection requires specific pipeline configurations, potentially disrupting operations [8,19,21,23,39,40]. Given these limitations, coupled with the scarcity of research focused on pipeline inspection for water supply systems in mining or rural settings, a comprehensive assessment of suitable inspection techniques is needed.

This study addresses this research gap by evaluating and comparing the performance, detection range, and operational suitability of GW, MMM, and ILI for detecting leaks and defects in mining water supply pipelines. This study facilitates more effective technology selection, contributing to long-term pipeline reliability, safety, and integrity management in mining systems. By demonstrating the benefits of a tailored technology approach for the unique operational challenges of mining environments, this research provides practical guidance for technology selection and supports the industry’s sustainability and efficiency goals.

2. Methodology

This study examines five primary aqueducts, named with terms derived from a blend of their geographical origins and local Quechua and Atacameño languages—Colaniqui, Inacatac, Salamari, Santaruna, and Tocontai—, each designed to meet different operational requirements in terms of length, diameter, and flow rate. These aqueducts form the backbone of the water transport systems that support mining operations in northern Chile at an altitude of 2870 m. The region’s harsh environmental conditions significantly impact pipeline operations [41,42]. Characterized by an arid climate, the area receives as little as 15 mm of rainfall annually, making it one of the driest places in the world. Diurnal temperature fluctuations are extreme, often ranging from −5 °C at night to 30 °C during the day, accelerating thermal stress on the pipelines. The area also experiences high winds, frequently exceeding 20–30 km/h. These winds carry abrasive sand particles that contribute to erosion and external corrosion of pipeline surfaces. Additionally, elevations across the region vary, reaching up to 3000 m above sea level. The harsh weather and lower atmospheric pressure at these higher elevations further complicate pipeline inspection and maintenance. These combined factors exacerbate pipeline corrosion risks and underscore the critical need for robust, complementary inspection and maintenance strategies to ensure operational reliability under such extreme conditions. To address these challenges, this study uses a systematic framework to compare and rank the effectiveness of various corrosion inspection technologies. This evaluation considers the unique needs of the mining sector, enabling the selection of methods capable of accurately assessing pipeline integrity under extreme environmental and operational conditions.

2.1. Integrated Methodology for Pipeline Inspection Technology Selection and Evaluation

The methodology includes three structured stages to identify suitable inspection technologies for a comprehensive pipeline integrity program in the mining industry. These stages include an initial diagnostic assessment of pipeline conditions, a literature-based selection of advanced inspection methods, and a feasibility analysis aligned with mining industry standards. Each technology is thoroughly evaluated to ensure compatibility with the specific requirements of large-scale water transport infrastructure in mining environments.

Figure 1 presents a flowchart for selecting and evaluating pipeline inspection technologies in this study. It includes three phases, namely diagnostic assessment, investigation and selection of technologies, and analysis of their applicability.

In the initial stage, a diagnostic evaluation of the current conditions and prevalent corrosion mechanisms in the water transport systems was conducted. This assessment aimed to establish baseline conditions and requirements for selecting suitable inspection technologies. Historical data and the current state of the water transport systems were analyzed to identify existing damage or deterioration mechanisms affecting pipeline integrity. This foundational analysis helped set the criteria for the next stage in the selection of technologies.

During the second stage, a literature review was conducted to identify and evaluate various pipeline inspection technologies that could address the identified corrosion mechanisms. This review encompassed scholarly publications and studies from databases such as Web of Science (WoS), Scopus, and Google Scholar, as well as technical documentation from service companies specializing in pipeline integrity and industrial inspection technologies. Both local and international sources were considered. The potential inspection technologies were selected based on their relevance to the specific operational demands of the pipeline systems under study.

In the final stage, the feasibility of each selected technology was analyzed. This involved detailing the characteristics of each technology, including the technology purpose, status, information sources, benefits, limitations, and scope of application. Key performance indicators were identified to facilitate a comparative evaluation, with these indicators being established based on the specific needs of the mining industry. The parameters were quantified using a two- and three-level scale rating system. Finally, the study assessed the applicability of each inspection technology to the water transport systems, considering whether each technique was disruptive or non-disruptive and the extent to which it could meet inspection requirements under the identified mining conditions.

Detailed information about each technology’s capabilities and limitations was gathered from research literature, case studies, and applications. The technologies were scored for each criterion based on their documented or anticipated performance. If certain criteria were more critical than others (for example, detection accuracy or reliability in high-risk environments), a weighted scoring system could be applied. This ensured that higher-priority aspects had a proportionate influence on the final assessment. The outcome of this framework is a ranked list of inspection technologies, where each technology is assessed in terms of its overall suitability for mining pipeline inspection. Based on the final scores and ranks, recommendations are made on which technologies, alone or in combination, are best suited to build a robust pipeline integrity management program for mining applications. This approach considers both the individual strengths of each technology and the potential benefits of combining multiple inspection methods for comprehensive coverage.

Each technology is rated on a scale that varies based on the nature of the criterion. Two-Level vs. Three-Level Scales: Some criteria (e.g., Analysis Method and Inspection Procedure) have two levels because their nature inherently involves binary distinctions (quantitative vs. qualitative, disruptive vs. non-disruptive). Others (e.g., Inspection Range, Market Accessibility, Inspection Preparation) have three levels, reflecting gradations of performance. This structured approach ensures accurate and tailored evaluation across diverse aspects of inspection technologies. (

Table 1. Rating Scale for Technology Performance Evaluation.

Criterion	Level	Score	Description
Aboveground Section Range	Low	2	Covers small areas or discrete sections (<10 m).
	Medium	4	Covers sections between 10 m and 1000 m.
	High	6	Covers extensive sections (>1000 m).
Buried Section Range	Low	2	Covers small or discrete buried sections (<10 m).
	Medium	4	Covers buried sections between 10 m and 1000 m.
	High	6	Covers buried sections extensively (>1000 m).
Market Accessibility	Low	2	Very limited availability, with minimal global presence.
	Medium	4	Moderately available, with limited competition.
	High	6	Widely available globally, with strong service support.
Analysis Method	Qualitative	3	Provides location data but lacks precision in damage severity quantification.
	Quantitative	6	Offers precise data, including severity assessment for informed decision-making.
Inspection Procedure	Disruptive	3	Requires operational interruption or physical access adjustments.
	Non-disruptive	6	Can be performed without disrupting pipeline operations.
Inspection Preparation	Minimal	2	Basic preparation such as calibration, with no additional steps.
	Moderate	4	Includes preparatory activities like cleaning or partial site modification.
	Extensive	6	Requires significant preparatory actions, including infrastructure adjustments or site changes.

).

Each technology receives a score in each category, allowing for a straightforward comparison and highlighting strengths and weaknesses across technologies using the summed scored.

This comparison framework provides a structured, quantitative approach to evaluating inspection technologies, allowing decision-makers to select methods that align with operational needs, industry standards, and budgetary constraints specific to the mining industry.

2.2. Operational Parameters for Each Inspection Technology

For Guided Wave Ultrasonic Testing (GWUT), low-frequency guided waves (20–100 kHz) are employed for long-range inspections, enabling the detection of large-volume defects such as wall thinning, uniform corrosion, and weld anomalies. GWUT’s effectiveness diminishes for small, localized defects (e.g., pitting corrosion), particularly at extended ranges or in pipelines with coatings and buried segments deeper than 1.5 m, where signal attenuation occurs. Soil factors, such as high moisture content, resistivity (<1000 Ω-cm), and low pH (<6.0), exacerbate attenuation, reducing detection reliability.

For Magnetic Metal Memory (MMM), variations in residual magnetic fields indicate stress concentration zones, which can signal early-stage cracks and localized corrosion. MMM’s sensitivity is influenced by soil properties, particularly resistivity and moisture content, which can distort magnetic field signals in semi-buried or buried pipelines. The method is particularly effective in detecting stress concentrations caused by soil-induced load conditions, such as differential settlement or pressure points near joints and soil interfaces.

In In-Line Inspection (ILI), Magnetic Flux Leakage (MFL) tools detect medium to large anomalies such as wall thinning, general corrosion, and mechanical damage with a sensor spacing of 2–3 mm. Ultrasonic Testing (UT) ILI tools achieve higher resolution with sensor spacing of 0.5–1 mm, enabling precise detection of pitting corrosion and stress-induced cracks. Soil-related factors, such as density, pH, and chemical composition (e.g., sulfates and chlorides), indirectly affect ILI performance by contributing to pipeline corrosion rates, which influence defect growth. To ensure optimal results, parameters such as flow rate, pipeline configuration (e.g., consistent diameter), and piggability must be carefully specified.

3. Water Transport Systems of Mining Industry: Evaluating Advanced Inspection Technologies

3.1. Characterizing Water Transport Systems

The case study investigates the mining industry’s water supply systems primarily source water from nearby mountain ranges and, to a lesser extent, the recovery of industrial wastewater from tailings ponds. These water sources are transported through various aqueducts constructed primarily from carbon steel (API 5L), which is commonly used for oil, gas, and liquid transportation such as steam, water, or slurry. Although some pipeline segments have been replaced over the years, the primary material has remained carbon steel with a thickness categorized as STD to align with industry standards.

The five main aqueducts, namely Colaniqui, Inacatac, Salamari, Santaruna, and Tocontai, have varying lengths, diameters, and flow rates, reflective of each aqueduct’s unique requirements.

• Colaniqui Aqueduct: Transports 50 L/s over 104 km with an elevation drop of 1350 m from the high Andes to mining site. This system has been operational since 1978 with an initial diameter of 16 inches, reducing to 12.7 inches toward the final section. Thickness ranges from 6.35 mm to 4.78 mm.
• Inacatac Aqueduct: Primarily supplies drinking water to the mining plant, carrying 155 L/s over 114 km from an elevation of 4041 m. Operational since 1956, the pipeline begins with a 20-inch diameter, reducing to 12 inches with thicknesses ranging from 7.92 mm to 6.35 mm.
• Salamari Aqueduct: This 73 km long system transports 470 L/s to mining facilities and features reinforced sections. Pipeline diameters vary between 22.0 and 35.8 inches, with thicknesses between 6.35 and 7.94 mm, indicative of the high-pressure requirements along its route.
• Santaruna Aqueduct: With the largest flow rate, the Santaruna aqueduct carries 950 L/s over 64 km. It has diameters ranging from 30.0 to 50.8 inches and thicknesses between 8.89 and 11.11 mm, meeting the heavy-duty needs of mining operations.
• Tocontai Aqueduct: The oldest, operating since 1919, this aqueduct spans 91 km, transporting 50 L/s with diameters ranging from 10.0 to 14.0 inches and thicknesses between 4.78 and 6.35 mm.

In the mining industry, water transportation pipelines and aqueducts face various environmental and operational challenges that can lead to different types of defects and corrosion mechanisms. The analysis of corrosion potential in water transport pipelines is focused on the internal and external mechanisms affecting five key aqueducts, namely Tocontai, Inacatac, Santaruna, Colaniqui, and Salamari. The assessment incorporates water chemistry indices (Langelier and Ryznar) and external soil aggressiveness parameters, identifying the main factors influencing the durability of steel pipes in these systems.

Internal Analysis of Water Corrosion and Scaling Using LSI and RSI Indices:

The Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI) were applied to evaluate the corrosive or scaling tendencies of the water transported through the aqueducts. The LSI provides a measure of water’s chemical balance, while the RSI incorporates empirical data to better estimate corrosion rates and film formation tendencies. The following insights emerged from the analysis.

The Tocontai aqueduct exhibited an LSI average of −0.7 (corrosive) and an RSI average of 9.3 (highly corrosive), with no formation of protective carbonate layers and pH values (7.4–8.6), indicating localized corrosion risks due to oxidizing agents and passive layer deterioration. The Inacatac aqueduct showed an LSI average of 0.2 (neutral to slightly scaling) and an RSI average of 7.7 (corrosive), where high dissolved oxygen levels and pH variability (7.4–8.7) promoted corrosion despite neutral LSI. In the Santaruna aqueduct, an LSI average of 1.0 (slightly scaling) and an RSI average of 6.3 (near equilibrium) indicated minimal carbonate formation, though localized corrosion remained a concern, particularly with fluctuating pH levels (7.5–8.6). The Colaniqui aqueduct, with an LSI average of 0.2 (neutral to slightly scaling) and an RSI average of 7.7 (near equilibrium but leaning corrosive), displayed higher susceptibility to corrosion in lower-speed sections (0.39–1.34 m/s) and pH values ranging from 7.2 to 8.7. Finally, the Salamari aqueduct had an LSI average of 0.8 (slightly scaling) and an RSI average of 6.6 (near equilibrium), where slight scaling tendencies were observed, but oxygen levels and pH (7.7–8.4) posed risks of localized corrosion.

Four aqueducts displayed significant corrosive potential according to RSI, underscoring localized corrosion risks from dissolved oxygen and pH fluctuations. The Tocontai and Inacatac aqueducts were the most vulnerable to internal corrosion due to high RSI scores and unfavorable water chemistry.

Soil Aggressiveness and corrosion impact:

The external corrosion analysis of the aqueducts, conducted using the DVGW GW9 standard, revealed varying levels of soil aggressiveness that significantly impact pipeline integrity.

The Tocontai aqueduct exhibited highly aggressive soil conditions with low resistivity values (<1000 Ω-cm), and elevated chloride and sulfate concentrations, leading to external corrosion rates exceeding 1.5 mm/year in critical zones. Buried segments at a depth of 1.2–1.5 m were particularly affected due to increased soil moisture and localized acidic pH values ranging between 5.8 and 6.2. The Inacatac aqueduct also experienced highly aggressive soil with 18 out of 20 analyzed samples showing low resistivity values. Corrosion hotspots were identified along deeper buried sections (up to 1.8 m), where external corrosion rates reached 1.2–1.4 mm/year. The primary contributing factors were chloride content and fluctuating soil moisture.

The Santaruna aqueduct presented similar challenges with aggressive soil conditions in approximately 70% of the analyzed locations. Low resistivity combined with elevated sulfate levels caused an estimated 1.0–1.3 mm/year material loss, particularly in buried segments prone to soil-water interface corrosion.

The Salamari aqueduct showed moderate-to-high aggressiveness, driven by localized chloride and sulfate concentrations. External corrosion rates of 0.8–1.1 mm/year were observed, predominantly at depths of 1.0–1.5 m, where soil pH remained acidic (around 6.0).

While most regions demonstrated weakly aggressive soil in the Colaniqui aqueduct, isolated highly corrosive zones were detected, particularly where soil moisture was highest. External corrosion rates were comparatively lower at 0.6–0.8 mm/year, but pipeline sections at shallow burial depths (<1 m) exhibited higher vulnerability to rapid material degradation.

Analysis of Corrosion Mechanism in mining water pipelines:

Corrosion in mine water pipelines and aqueducts is a multifaceted challenge driven by mechanisms such as uniform corrosion (Figure 2a), galvanic corrosion (Figure 2b), pitting corrosion (Figure 2c), and erosion corrosion (Figure 2d). Uniform corrosion is the most prevalent form and affects the entire pipe surface uniformly due to exposure to environmental factors, high mineral content, and fluctuating pH levels. For example, in the Santaruna aqueduct, slightly scaling water, indicated by its LSI values, combined with pH levels ranging from 7.5 to 8.6, promotes the development of uniform corrosion, particularly in externally exposed sections. Similarly, the Colaniqui aqueduct, with moderate flow velocities between 0.39 and 1.34 m/s, shows vulnerability in lower velocity areas prone to uniform corrosion.

Galvanic corrosion (Figure 2b) occurs when dissimilar metals in contact are exposed to an electrolyte such as water or wet soil. This mechanism is prevalent in mining pipelines where material diversity is common. Soil aggressiveness plays a critical role in external galvanic corrosion, as evidenced by the Tocontai and Inacatac aqueducts, which had highly aggressive soil samples in 14 and 18 cases, respectively. Low resistivity (<1000 Ω-cm), coupled with high chloride and sulfate content, enhances the electrochemical environment that accelerates corrosion.

Pitting corrosion (Figure 2c), characterized by localized, deep pits or holes, is a significant problem in water with high chloride concentrations or low pH [43]. This form of corrosion results from the breakdown of the protective passive oxide layer by oxidizing agents [44]. For example, the Tocontai aqueduct has high RSI values (average 9.3), confirming the corrosiveness of the water, with pH values between 7.4 and 8.6 exacerbating localized corrosion risks. The Inacatac aqueduct, although neutral on the LSI scale (average 0.2), experiences pitting due to high velocities (0.76–2.12 m/s) and variable pH (7.4–8.7). These conditions increase the risk of pitting and material degradation, especially in critical areas.

Erosion corrosion is primarily caused by the relative movement of the transported fluid against the inner surface of the pipe. Fluid turbulence can cause a rapid increase in the erosion rate, and if the fluid also contains suspended solid particles, the erosive effect tends to be further accelerated due to the deterioration of the metal. This type of corrosion is detected in the Tocontai aqueduct, as shown in Figure 2d.

To effectively address these challenges, inspection technologies are essential in identifying early signs of corrosion and structural weaknesses. Additionally, preventive measures such as using protective coatings, implementing cathodic protection, and selecting materials with high corrosion resistance in design stage can help mitigate these risks. For operating system investigated, integrating advanced inspection technologies with preventive strategies, the mining industry can improve the durability, reliability, and safety of its water transport infrastructure.

3.2. Preliminary Selection of Potential Pipeline Inspection Technologies

The evaluation identified primary inspection technologies suitable for water pipelines in the mining industry, namely Guided Wave Ultrasonic Testing (GWUT), Remote Field Eddy Current (RFEC), Magnetic Flux Leakage (MFL), Metal Magnetic Memory (MMM), and In-Line Inspection (ILI).

Guided Wave Ultrasonic Testing (GWUT) is a non-disruptive technique that utilizes ultrasonic waves to inspect pipeline conditions from a single access point. This method allows for comprehensive 360-degree coverage and is effective in detecting corrosion, wall thinning, and other structural anomalies, even in pipelines with insulation or coatings. GWUT’s non-intrusive nature minimizes operational disruptions, making it particularly advantageous in mining environments where halting operations can be costly. However, GWUT has limitations, particularly in buried pipelines where signal attenuation can hinder its effectiveness over long distances, typically beyond 30 m. Additionally, it is less effective at distinguishing between internal and external corrosion and is limited in pipelines with bell-and-spigot joints or extensive coatings that impede signal transmission.

Remote Field Eddy Current (RFEC) technology leverages electromagnetic induction to detect corrosion and structural defects within the pipeline material, proving highly effective for in-line inspections. RFEC excels in generating high-resolution imaging over long distances, allowing for comprehensive structural assessments. This technology is also non-intrusive and capable of detecting both internal and external corrosion simultaneously, providing critical insights into pipeline integrity and material composition. Despite these advantages, RFEC requires accessible pipeline segments compatible with inline inspection devices and works best with pipelines that maintain consistent diameter and wall thickness. These requirements can restrict its application in certain mining pipeline segments that may not conform to such specifications.

Magnetic Flux Leakage (MFL) uses magnetic fields to detect structural anomalies in ferromagnetic pipelines by identifying distortions caused by metal loss or damage. MFL provides high-resolution imaging that supports thorough structural assessments and is effective for surface and subsurface inspection in ferromagnetic materials. Additionally, MFL quantifies the severity of detected damage, improving the accuracy of risk assessments and enabling proactive maintenance. However, its application is limited to ferromagnetic pipelines, excluding its use in non-metallic or non-ferromagnetic materials. Moreover, MFL’s implementation can be costly due to the need for specialized equipment and skilled operators, which may increase operational expenses.

Metal Magnetic Memory (MMM) focuses on early-stage failure detection by identifying stress concentration zones and fatigue damage. While MMM shows promise for mining pipeline conditions, especially in detecting early-stage corrosion and fatigue, its use is restricted to ferromagnetic materials and may be impacted by magnetic interference from nearby pipelines, limiting its utility in some mining environments. Together, these technologies offer a range of inspection capabilities that, when chosen and applied strategically, can significantly enhance pipeline integrity management in the mining sector.

In-Line Inspection (ILI) technology employs advanced multi-sensor robotic platforms that incorporate various sensing mechanisms, such as Magnetic Flux Leakage (MFL) and Ultrasonic Testing (UT), to detect corrosion and structural defects within the pipeline material, proving highly effective for internal inspections. These robotic ILI tools excel in generating high-resolution imaging over long distances, allowing for comprehensive structural assessments. The technology is non-intrusive and capable of detecting both internal and external corrosion simultaneously, providing critical insights into pipeline integrity and material composition. Despite these advantages, ILI requires accessible pipeline segments compatible with in-line inspection devices and is most effective with pipelines that maintain consistent diameter and wall thickness. These requirements, along with the need for specific pipeline geometries to accommodate the robotic platform, can restrict ILI’s application in certain mining pipeline segments that may not conform to such specifications.

Advanced inspection technologies are critical for detecting early signs of corrosion and structural weakness in mine water pipelines. Non-disruptive methods such as Guided Wave Ultrasonic Testing and Magnetic Flux Leakage are highly effective in detecting uniform corrosion. These technologies provide comprehensive coverage of large sections of pipeline and allow consistent assessment of wall thickness without disrupting operations. For example, Figure 3a shows GWUT being applied to an above-ground pipeline, where transmitted and reflected waves enable the identification of uniform corrosion and wall thinning, even in inaccessible sections.

Galvanic corrosion, which typically results from contact between dissimilar metals, can be effectively monitored using electrical continuity testing, potential difference measurements, and targeted visual inspections of high-risk joints and soil interfaces. For stress-related weaknesses, Figure 3b depicts the Magnetic Metal Memory technique, where a specialized device attached to the pipeline surface detects stress concentration zones that could lead to early failures, particularly in harsh mine water environments.

Following a detailed analysis of the mine water pipeline requirements and a thorough evaluation of advanced inspection methods, three technologies were selected for suitability, namely Guided Wave Ultrasonic Testing, Magnetic Metal Memory, and In-Line Inspection. Figure 3c presents the smart ball technology, which uses integrated acoustic and magnetometer sensors to detect leaks in submerged or semi-buried pipelines.

To detect pitting corrosion, which is more localized, techniques such as eddy current testing or high-resolution ultrasonic scanning offer precise detection of small, deep defects. Figure 3d highlights multiple ultrasonic transducers integrated into a robotic tool, enabling high-resolution scanning of localized pitting corrosion inside semi-buried or buried pipelines.

Additionally, Figure 3e showcase robotic ILI tools with MFL spiral and axial sensors, combined with electromagnetic acoustic transducers, which address the challenges of detecting corrosion in buried and semi-buried pipelines while maintaining accuracy and reliability in harsh conditions.

3.3. Qualitative Evaluation of Inspection Techniques

Each technology’s effectiveness was rated based on parameters critical to the mining sector.

Table 2. Effectiveness Ratings of Pipeline Inspection Technologies.

Aspect	GWUT	MMM	ILI
Aboveground Section Range	4	6	6
Buried Section Range	4	6	6
Market Accessibility	6	4	6
Analysis Method	3	3	6
Inspection Procedure	6	6	3
Inspection Preparation	4	4	2
Total Score	27	29	29

presents the scores for above-ground and buried inspection ranges, market accessibility, analysis method, and inspection procedure for each technique.

Figure 4 presents a radar chart comparing the suitability of different technologies for the case study mining site. In-Line Inspection (ILI) technology achieved high scores (29 out of 36) in the evaluation due to its exceptional capacity for providing extensive, high-resolution data on pipeline integrity. ILI’s ability to inspect both aboveground and buried pipeline segments over long distances offers substantial advantages, especially for pipelines extending across vast areas typical in mining operations. Unlike methods limited to specific pipeline sections, ILI tools can continuously inspect both exposed and buried sections as they traverse the pipeline, allowing for seamless data collection across various terrains. This capability ensures consistent, high-quality data over the entire length of the pipeline, facilitating a comprehensive integrity assessment with minimal manual intervention. ILI’s long-range inspection and self-contained operation make it particularly suitable for mining pipelines that may traverse inaccessible or challenging terrains. Additionally, ILI’s market accessibility is high, as it is a well-established technology in the oil and gas sectors, supported by a wide array of vendors and service providers. This widespread adoption ensures that mining operations can easily source the necessary tools, expertise, and support for ILI deployment, enhancing its overall attractiveness for industrial applications.

Our analysis of the strengths and limitations of ILI technology is supported by previous research [31], which emphasizes ILI’s robust data collection and high-resolution imaging capabilities. Further contributing to ILI’s strong evaluation is its quantitative and highly detailed data collection, scoring it high in analysis capability. ILI technology provides precise measurements on internal and external pipeline conditions, covering factors such as wall thickness, corrosion depth, and structural deformations. Its sophisticated sensors offer high-resolution imaging, enabling the detection and quantification of minor flaws that may indicate potential failure points. This precision is crucial in assessing pipeline structural health and enables data-driven maintenance decisions. However, ILI technology scored lower on inspection procedure (3 out of 6) due to its disruptive requirements, as it often necessitates operational adjustments, including controlled flow rates and the installation of launching and receiving stations, which can add logistical complexity. Additionally, pipelines must meet specific “piggable” criteria, such as consistent diameter and minimal bends, which may require modifications—particularly challenging in older mining pipelines.

Guided wave ultrasonic testing (GWUT) received low scores (4/6) in several areas due to its inspection limitations and practical constraints, especially in the mining industry. Guided wave technology uses ultrasonic waves that weaken over long distances and in buried pipelines, limiting their effective range to about 30 m or less. This requires multiple access points and inspections in large pipeline networks. In addition, in buried sections, the technology requires periodic excavations to access and reapply the probe, making it less suitable for long, continuous pipelines in mining. In addition, the GWUT cannot differentiate between internal and external corrosion, making it difficult to make specific maintenance decisions. These limitations affect the overall feasibility and effectiveness of the technology. Our findings align with reported research on recent advances in ultrasonic guided wave technology, which have progressed with potential for detecting corrosion defects in pipelines in long range coverage and high sensitivity by employing Lamb and shear horizontal waves, while some limitations to detect local small defects still exist [21].

Magnetic metal memory (MMM) techniques score lower in accessibility due to several factors. First, specialized equipment and expertise are required to use this technology, which may limit its availability compared to other inspection techniques. In addition, MMM relies on specialized operators to interpret magnetic field data, which may limit the number of available providers. There is also a limited presence of MMM service providers compared to more established technologies, which restricts its accessibility in international markets. MMM is also less deployed in mining applications compared to other technologies, which further reduces the number of companies offering specialized services in mining pipelines. In addition, there are regional and environmental constraints that may affect the use of MMM in certain locations. In summary, the accessibility of MMM is affected by the availability of specialized equipment and operators, as well as the lack of suppliers and low usage in mining applications. Analysis of the accessibility limitations of Magnetic Metal Memory (MMM) techniques is consistent with findings by Villegas-Saucillo et al. [45], who emphasize that although MMM can provide critical real-time defect monitoring, it is hindered by specialized equipment and expertise requirements. This reliance on high-resolution sensors and skilled operators limits MMM’s deployment in broader industries, especially mining. Its accessibility is further restricted by limited service providers and regional constraints, reducing its utility in pipeline inspection.

In conclusion, adopting a multi-technology inspection approach is determined as the key factor to ensure the long-term reliability and sustainability of critical water transport infrastructure in the mining sector.

4. Limitations and Recommendations

This study is primarily qualitative and exploratory. Due to its preliminary nature, a comprehensive quantitative analysis of detection accuracy and method comparison was not feasible. However, the evaluation of different technologies’ applicability provides crucial guidance for future research.

Future research will quantify the cost-effectiveness and performance limitations of advanced inspection methods in the mining industry. This will involve collecting data on detection probability, sizing accuracy, and false positive/negative rates for Magnetic Flux Leakage and Ultrasonic Guided Wave of In-Line Inspection technologies. A robust comparison of these methods will inform best practices for pipeline integrity management. Each technique has limitations: Guided Wave Ultrasonic Testing is less effective over long distances in buried sections due to signal decay; Metal Magnetic Memory is limited to ferromagnetic materials; and ILI is generally infeasible for low-pressure or irregularly constructed pipelines. In addition, other parameters for performance evaluation could include the operation risk, the accuracy or the reliable of the inspection data [46].

This study focused on specific water supply pipelines in the mining sector. Future research should expand this scope to include cost–benefit analyses, other pipeline types (e.g., slurry transport), collaborative frameworks and partnerships to develop innovative solutions, and asset management systems integrating inspection data for informed decision-making. Further research could also enhance corrosion mapping capabilities in geodynamically active regions, examine the economic impact of advanced techniques on pipeline longevity, and assess the suitability of specific commercial ILI technologies (e.g., SmartBall^® [47]) and robotic solutions integrating UT, MFL, and Electromagnetic Acoustic Transducer sensors (e.g., UT-CS HAWK^® [48], as well as SpirALL^® MFL/EMAT [49]) for mining operations.

5. Concluding Remarks and Future Research

This study provided a qualitative and exploratory evaluation of pipeline inspection technologies tailored to the specific demands of the mining industry’s water transportation infrastructure. While a comprehensive quantitative analysis of detection accuracy and cross-method comparison was beyond the scope of this stage of research, the study establishes a foundational understanding of the applicability of various technologies under specific operational conditions, providing valuable direction for future research.

The findings highlight that each technology presents unique strengths under particular operational conditions: Metal Magnetic Memory (MMM) proves highly effective for early corrosion detection in remote and hard-to-reach locations, while Guided Wave Testing (GW) excels in identifying surface anomalies with efficiency. In contrast, In-Line Inspection (ILI) offers the most comprehensive structural assessment but is best suited to pipelines with compatible infrastructure and stable operational conditions, as it presents challenges in high-pressure segments and short pipeline sections.

The selection of inspection technology should align closely with the specific attributes of the pipeline system, environmental conditions and budgetary constraints. In particular, Magnetic Flux Leakage and Ultrasonic Guided Wave technologies hold promise for the mining sector due to their capacity to assess both internal and external conditions, including buried and coated sections, without operational disruptions. GW and MMM are non-disruptive but limited by constraints on pipeline depth and diameter, while ILI, which is capable of detailed analysis, requires “piggable” pipeline conditions, excluding up to 50% of pipelines globally that lack such compatibility.

Considering the case study, prioritization of high-criticality aqueducts results in the selection of the Salamari, Santaruna, and Inacatac aqueducts for inspection, as these account for 84.8% of total water transport, while lower-criticality aqueducts (Colaniqui and Tocontai, collectively transporting 5.8%) are less suited to ILI due to operational restrictions. Furthermore, MMM scored a “high” rating overall (29/36), exceeding GW’s score (27/36) because of its superior market availability and ease of preparation, while ILI, despite its high total score (29/36), scored lower in inspection preparation due to logistical complexities.

Future research should prioritize quantifying the cost-effectiveness and performance limitations of advanced pipeline inspection methods within the mining industry. This involves gathering data on key performance indicators, such as probability of detection, sizing accuracy, and false positive/negative rates for technologies like Magnetic Flux Leakage, Ultrasonic Guided Wave, and In-Line Inspection. It should also incorporate additional performance parameters such as operation risk, data reliability, and accuracy across different pipeline conditions. A robust comparison of these methods will inform best practices for pipeline integrity management in mining applications.

An integrated inspection strategy combining the strengths of these technologies is recommended for effective and sustainable pipeline management. Further research should also focus on enhancing corrosion detection precision in geologically active regions, particularly for semi-buried pipelines in variable soil conditions. Additional research areas include the following topics: quantifying the cost-effectiveness and operational limitations of advanced methods in mining; optimizing inspection technologies for non-standard pipeline configurations (e.g., high-pressure, short segments); developing data integration frameworks to consolidate insights from multiple inspection tools; and exploring innovative sensing and robotics-enabled solutions for improved inspection access in remote mining settings. Collaboration with research institutions and technology providers is essential to advancing these capabilities and building safer, more sustainable, and efficient water transportation infrastructure for the mining industry.