Published on 10-Oct-2020

Corrosion Detection in Large Ferrous Pipes - Remote Field Array Technology

Corrosion Detection in Large Ferrous Pipes - Remote Field Array Technology

Sources - Eddyfi Technologies

Table of Content

Large ferrous pipes present unique challenges in terms of size and structural complexity. Traditional inspection methods often struggle to adequately penetrate and assess these materials, particularly in areas with bends, varying thicknesses, or extensive lengths. Corrosion, a pervasive threat in industrial settings, can compromise pipeline integrity and necessitate costly repairs if not detected early and accurately.

Remote Field Array (RFA) technology represents a pivotal advancement in addressing these challenges. By leveraging arrays of sensors and advanced electromagnetic techniques, RFA probes can achieve unprecedented sensitivity and coverage during inspections. This capability allows for comprehensive assessments of internal pipe conditions, identifying minute defects and corrosion patterns that might remain undetected.

Remote Field Array Technology: An Overview

RFA technology represents a significant advancement in Non-destructive Testing, specifically tailored to address challenges in inspecting large ferrous pipes for corrosion and defects. 

This technique builds upon the foundational Principles of Remote Field Testing, a form of electromagnetic inspection known for its ability to penetrate deep into conductive materials like steel.

The roots of remote field electromagnetic testing can be traced back to early efforts in electromagnetic inspection methods detecting flaws beyond the surface of metallic structures. 

RFT techniques have evolved to encompass more sophisticated approaches, culminating in the development of RFA probes.

Principles of Remote Field Technology

Principles of Remote Field Technology

The principles of Remote Field Array Technology are as follows:

  • Remote Field Testing operates on the principle that alternating magnetic fields induced externally can penetrate deep into conductive materials, such as ferrous metals.
  • Unlike surface inspection methods, RFT probes can detect defects and corrosion beyond the immediate surface, providing comprehensive structural integrity assessment.

Electromagnetic Principles:

  • RFT relies on the interaction between external alternating magnetic fields and the conductive material of the pipe wall.
  • When an alternating current passes through a coil in the probe, it generates a changing magnetic field around it.
  • This alternating magnetic field induces eddy currents in the conductive pipe wall, according to Faraday's Law of Electromagnetic Induction.
  • The interaction between these induced currents and the magnetic field produces secondary magnetic fields within the pipe wall.
  • These secondary fields vary based on the material's conductivity and anomalies like corrosion or defects.
  • By measuring changes in the induced secondary fields, RFT probes can identify and characterise internal anomalies, including corrosion and wall thickness variations.

Application in Corrosion Detection:

  • Remote Field Testing is particularly effective for detecting corrosion in ferrous materials.
  • Corrosion often alters the conductivity and thickness of the pipe wall, affecting the induced eddy currents and secondary magnetic fields.
  • Variations in these fields, detected by the RFT probe, indicate the presence and severity of corrosion, even in areas inaccessible to direct inspection.
  • This capability allows early detection and assessment of corrosion-related risks, supporting proactive maintenance and Integrity Management Strategies.

Remote field testing leverages electromagnetic principles to penetrate ferrous materials and detect internal anomalies such as corrosion and defects. Its ability to assess structural integrity beyond surface-level inspections makes it a valuable tool in industrial settings, contributing to efficient maintenance and safety management practices.

Sensitivity and Detection Capabilities

Sensitivity and Detection Capabilities

The sensitivity and detection capabilities of Remote Field Array Technology include:

1. Enhanced Penetration Depth:

  • RFA offers enhanced penetration depth compared to conventional surface inspection methods.
  • Utilising alternating magnetic fields, RFA probes can detect defects and corrosion deep within ferrous materials, beyond surface layers.

2. Detection of Internal Anomalies:

  • The technology can detect internal anomalies such as corrosion, erosion, and pitting within pipes and tubes.
  • By inducing eddy currents in the conductive material, RFA probes measure changes in electromagnetic responses indicative of structural abnormalities.

3. Accurate Measurement of Wall Thickness:

  • RFA probes accurately measure wall thickness variations due to corrosion or material degradation.
  • This capability supports the assessment of remaining wall thickness, for determining structural integrity and operational safety.

4. Quantitative Assessment of Defect Severity:

  • RFA technology provides quantitative data on defect severity and extent, aiding in prioritising maintenance and repair interventions.
  • By analysing variations in electromagnetic signals, engineers can assess the risk of failure and plan remedial actions accordingly.

5. Suitability for Complex Geometries:

  • RFA probes are suitable for inspecting complex geometries and areas inaccessible to traditional inspection methods.
  • This versatility enables comprehensive evaluation of pipelines, bends, and joints without compromising inspection accuracy.

6. Integration with Data Analysis Tools:

  • Remote Field Array Technology integrates with advanced data analysis tools to enhance defect characterisation and reporting.
  • Software algorithms analyse electromagnetic signals to generate detailed reports, supporting informed decision-making in asset management.

Remote Field Array Technology excels in detecting internal anomalies and measuring wall thickness variations in ferrous materials. Its enhanced sensitivity and capability to penetrate deep into structures make it an invaluable tool for corrosion detection and structural integrity assessment in industrial applications.

Inspection Range and Pipe Characteristics

RFA Inspection Range

The inspection range and pipe characteristics of RFT are as follows:

1. Versatile Application Range:

  • RFA is applicable across a wide range of pipe diameters, from small bore tubes to large diameter pipelines exceeding 150m.
  • This versatility ensures comprehensive coverage for various industrial applications requiring corrosion detection and structural integrity assessment.

2. Effectiveness in Different Pipe Materials:

  • RFA probes help inspect ferrous materials, including carbon steel, stainless steel, and other alloys.
  • The technology adapts to different material compositions and pipe wall thicknesses, providing reliable inspection outcomes irrespective of material variations.

3. Accommodation of Pipe Characteristics:

RFA technology accommodates pipes with multiple bends, elbows, and varying wall thicknesses without compromising inspection accuracy.

  • The probes maintain consistent sensitivity across complex geometries, ensuring thorough evaluation of critical pipeline sections.

4. Optimal Performance in Challenging Environments:

  • RFA probes perform reliably in harsh and challenging environments, such as offshore installations and industrial plants.
  • They withstand operational conditions involving high temperatures, pressures, and corrosive substances, supporting continuous monitoring and maintenance planning.

5. Precision in Wall Thickness Measurement:

  • The technology offers precise measurement of wall thickness variations along the entire length of the pipe.
  • This capability facilitates a detailed assessment of corrosion levels and remaining wall thickness, essential for integrity management and risk mitigation strategies.

6. Integration with Pipeline Management Systems:

  • RFA inspections integrate seamlessly with Pipeline Management Systems, enhancing data interoperability and workflow efficiency.
  • Real-time data acquisition and analysis support proactive decision-making in maintenance and repair activities, ensuring asset reliability and operational safety.

Remote field array technology excels in inspecting pipes of varying diameters and characteristics, providing accurate corrosion detection and structural assessment across diverse industrial settings. Its adaptability and reliability make it a preferred choice for ensuring pipeline integrity and operational continuity.

Data Acquisition and Storage

The data acquisition and storage in the RFT process include:

1. Real-time Data Collection:

  • Remote Field Array Technology utilises advanced sensors to collect real-time data during inspections of tubes and pipelines.
  • Sensors embedded in the probes detect electromagnetic responses induced in the pipe walls, providing immediate feedback on structural integrity and corrosion presence.

2. Electromagnetic Response Analysis:

  • During inspections, alternating magnetic fields generated by the RFA probes induce currents in the ferrous material of the pipes.
  • Variations in these induced currents are meticulously measured and analysed to identify corrosion spots, wall thinning, and other defects.

3. Onboard Data Processing:

  • Probes are equipped with data acquisition systems, capable of processing electromagnetic signals in real-time.
  • This onboard processing optimises data accuracy and reliability, supporting prompt maintenance and operational planning.

4. Storage in Solid-State Drives (SSD):

  • Captured inspection data is stored in onboard Solid-State Drives (SSDs) within the RFA probes.
  • SSDs offer high-speed data transfer capabilities and robust storage capacity, ensuring secure retention of inspection records for subsequent analysis.

5. Transfer to External Devices:

  • Post-inspection, data stored in SSDs is transferred to external devices, such as computers or data servers, for detailed analysis and reporting.
  • This transfer process facilitates a comprehensive assessment of corrosion levels, defect types, and pipeline conditions, for maintenance strategies.

6. Integration with Data Management Systems:

  • RFA technology integrates seamlessly with enterprise-level data management systems, enhancing data interoperability and accessibility.
  • Integration allows for centralised storage, retrieval, and archival of inspection data, supporting long-term asset management and regulatory compliance.

7. Enhanced Reporting Capabilities:

  • Inspection data processed and stored by RFA systems enables the generation of comprehensive inspection reports.
  • Reports include detailed findings, graphical representations of corrosion profiles, and recommendations for corrective actions, ensuring informed decision-making by stakeholders.

Remote Field Array Technology employs sophisticated data acquisition and storage mechanisms to conduct precise and efficient inspections of tubes and pipelines. By leveraging electromagnetic techniques, RFA ensures thorough corrosion detection and structural assessment, contributing to the reliability and longevity of industrial assets.

Data Transfer and Analysis

Data Transfer and Analysis

The data transfer and analysis of RFT involves the following:

1. Secure Data Transfer Protocols:

  • Remote Field Array Technology employs secure protocols for transferring inspection data from onboard storage to external analysis systems.
  • Data integrity and confidentiality are prioritised during transfer to prevent unauthorised access and ensure compliance with data protection regulations.

2. Integration with Analysis Software:

  • Inspection data acquired through RFA systems is integrated with advanced analysis software designed for Remote Field Electromagnetic Testing (RFET).
  • Analysis software processes electromagnetic responses induced in tube walls to identify corrosion, wall thinning, and other structural anomalies.

3. Quantitative Assessment of Defects:

  • Analysis software provides quantitative measurements of corrosion depths, defect sizes, and spatial distributions within inspected tubes.
  • This quantitative data facilitates precise Assessment of Pipeline Conditions, supporting informed decisions on maintenance and repair strategies.

4. Visualisation Tools for Interpretation:

  • Graphical visualisation tools embedded in analysis software display corrosion profiles and defect maps derived from RFA inspections.
  • Visual representations aid engineers and inspectors in interpreting inspection results and identifying critical areas requiring attention.

5. Statistical Analysis and Trend Monitoring:

  • Analysis software performs statistical analysis on inspection data to identify trends in corrosion rates and defect propagation over time.
  • Trend monitoring enables proactive maintenance planning and prediction of pipeline integrity based on historical data trends.

6. Reporting and Documentation:

  • Comprehensive inspection reports are generated by analysis software, summarising findings from RFA inspections.
  • Reports include detailed descriptions of detected defects, analysis methodologies, and recommendations for mitigation actions to maintain pipeline integrity.

7. Integration with Asset Management Systems:

  • Data transfer protocols facilitate seamless integration of inspection results with enterprise asset management systems (EAMs).
  • Integration supports the lifecycle management of industrial assets by aligning inspection data with maintenance schedules and regulatory compliance requirements.

8. Collaborative Analysis and Decision Support:

  • Analysis software enables collaborative analysis among multidisciplinary teams, including engineers, technicians, and regulatory authorities.
  • Collaborative platforms facilitate consensus building on maintenance priorities and operational decisions based on comprehensive inspection data.

Remote Field Array Technology enhances data transfer and analysis capabilities in Remote Field Testing, leveraging advanced software tools for accurate corrosion detection and structural assessment in tubes and pipelines. 

By integrating secure data protocols and analysis software, RFA systems support informed decision-making and proactive maintenance strategies to ensure the reliability and longevity of industrial assets.

Design and Engineering of RFT Array Probes

The design considerations behind RFT Array probes include:

1. Material Selection: RFT Array probes are typically constructed from materials that offer durability and electrical conductivity, such as stainless steel or non-magnetic alloys. These materials ensure minimal interference with the electromagnetic fields used in remote field electromagnetic testing.

2. Sensor Placement: The placement of sensors in RFT Array probes is critical for achieving accurate and comprehensive inspection results. Sensors are strategically positioned to maximise coverage of the pipe surface and to optimise the detection of corrosion and defects in remote field testing of tubes.

3. Electronics Integration: RFT Array probes integrate advanced electronics, including PCBs (Printed Circuit Boards) and signal processing units. These components facilitate real-time data acquisition, processing, and transmission during inspections. The electronics integration ensures the probe can handle the complex electromagnetic signals generated and received during remote field electromagnetic testing.

4. Remote Field Technique: RFT Array probes leverage the remote field technique, which involves inducing alternating magnetic fields in the pipe wall. These fields generate eddy currents that penetrate through the material, allowing detection of corrosion and defects beyond the surface. This technique is crucial for achieving accurate and reliable results in remote field electromagnetic testing applications.

5. Corrosion Detection: The primary objective of RFT Array probes is corrosion detection in tubes and other ferrous materials. By utilising remote field electromagnetic testing, these probes can identify corrosion, pitting, wall thinning, and other forms of degradation that may compromise the structural integrity of pipes.

6. Remote Field Array Technology: RFT Array probes have multiple sensors arranged in an array configuration. This technology enables comprehensive coverage of large pipe sections, including those with bends and complex geometries. The array design ensures thorough inspection and enhances the effectiveness of corrosion detection efforts.

These design considerations ensure they can deliver accurate, efficient, and reliable results in remote field electromagnetic testing applications for corrosion detection in industrial settings.

SG NDT has developed a series of autonomous RFT Array probes with increased sensitivity for the detection of small defects for the inspection of pipes over 150m with several bends. The probe contains a series of housing units in which all the required electronics (PCBs, batteries, etc.) perform data acquisition. As the probe is pulled in the pipe section, all data is recorded by an onboard SSD storage. Once the inspection is complete, the probe is connected to the computer for data transfer and analysis.

Future Trends and Innovations

RFT Future Trends

Innovations in remote field electromagnetic technique focus on enhancing RFT Array technology's sensitivity, sensor efficiency, signal processing, and material integration for improved remote field electromagnetic testing. 

  • Advancements will include AI and Machine Learning for Automated Defect Recognition, reducing human error, and speeding up remote field testing of tubes. 
  • Real-time monitoring capabilities will detect corrosion and defects immediately, enhancing safety and reliability using the remote field technique. 
  • Predictive maintenance will leverage data analytics and predictive modelling to forecast potential failures, aligning with remote field electromagnetic testing principles for proactive infrastructure maintenance. 
  • Innovations will also focus on advanced data acquisition and high-speed processing, ensuring detailed inspection results and comprehensive corrosion detection in remote field-testing applications. 
  • Miniaturisation of RFT Array probes will improve portability and deployment in confined spaces, broadening the applicability of remote field electromagnetic testing. 

Additionally, future developments will integrate RFT Array technology with other NDT methods, such as Ultrasonic Testing, for comprehensive material integrity assessment. Lastly, innovations will enhance environmental safety and operator protection, ensuring remote field electromagnetic testing remains a safe and eco-friendly inspection method.

Key Takeaways

  • Remote Field Array Technology provides deep penetration and high sensitivity for detecting internal anomalies and corrosion in large ferrous pipes.
  • Integration of advanced data acquisition, storage, and analysis techniques ensures precise and reliable inspection results, supporting proactive maintenance strategies.
  • Ongoing advancements, including AI and real-time monitoring, will further enhance the capabilities and applications of Remote Field Array Technology in industrial settings.


1. What is Remote Field Array Technology?

A: Remote Field Array Technology is an advanced NDT method that uses electromagnetic techniques to detect corrosion and defects deep within ferrous materials, providing comprehensive structural assessments.

2. How does Remote Field Array Technology enhance corrosion detection in large ferrous pipes?

A: By employing arrays of sensors and sophisticated electromagnetic methods, Remote Field Array Technology achieves high sensitivity and deep penetration, enabling the detection of minute defects and corrosion patterns that traditional inspection methods might miss.


1. Materials Performance

2. Kanwade Group


4. CMS Eddy Scan

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