Alternating Current Field Measurement (ACFM)

The Amigo by TSC provides operators with all the functionality and advantages of TS’s Alternating Current Field Measurement (ACFM) technology in a convenient portable package. With its reliable crack detection capabilities and accurate sizing using a rapid scanning technique with a handheld probe, the Amigo streamlines inspection campaigns while reducing cleaning requirements, as there is no need to clean to bare metal. Moreover, the Amigo boasts a long battery life and is a rugged site unit, rated to IP54.

Key Features of The Amigo:

  • Rapid scanning using a handheld probe
  • Reliable crack detection with accurate sizing (length and depth)
  • Reduced cleaning requirements, no need to clean to bare metal
  • At least 5 hours of operation on one fully charged battery pack, with easy battery pack exchange in the field
  • Main-powered battery charger for use with 110 to 240V AC (50 or 60 Hz)
  • Assist software (Microsoft Windows) for ease of operation and compatibility with other Windows applications
  • Full data storage for backup, offline view, and audit purposes
  • On-board buttons for RUN/STOP and MARKERS, as well as larger probes to allow one-man operation in difficult access areas

ACFM Tank Floor Weld Inspection

Petrochemical storage tanks are intricately constructed using rectangular steel plates overlapped and lap-welded to form the main tank floor. Surrounding the tank's perimeter, petal-shaped plates are arranged in a circular fashion and butt-welded together. The tank wall plates are then affixed using fillet welds to the outer floor plates. These construction methods pose unique challenges for defect inspection, prompting TSC to develop specialized solutions.

TSC’s ACFM® solutions offer reliable and swift inspection of tank floor welds without the need for extensive cleaning or coating removal. By providing valuable insights into crack depth, our solutions enable prioritized repairs and ensure comprehensive recording and reporting of data for audit purposes.

Inspection Challenge: The primary failure point in storage tanks often stems from corrosion in the floor plates, whether originating from the top surface or the underside. While well-established methods like magnetic flux leakage, low-frequency eddy currents, or ultrasonic inspections can detect plate thickness, they are unable to inspect welds for defects. Traditional technologies such as magnetic particle inspection (MPI) necessitate extensive surface cleaning and offer limited insight into defect depth.

The ACFM® technique was specifically engineered to detect and size surface-breaking defects at welds, capable of penetrating several millimeters of non-conductive coating. Unlike MPI, ACFM's signal strength correlates with defect size, enhancing the detection probability for significant defects.


ACFM® Array Probe Inspection

If inspection of all welds on the tank floor is required, the speed of the process can be increased using TSC’s adjustable array probe. With eight sets of sensors and housed in an independently sprung module, the probe can be “set” to match any weld profile and cap width. The adjustable array probe also has an onboard position encoder to automatically record defect locations and to regulate data collection. Novel Array Probes have also been specifically designed for inspecting the fillet weld at the wall-to-floor joint. A more “Compact Design” has been developed for inspecting a narrow range of cap widths. This model has one fixed sensor module for inspecting the floor toe and the heat-affected zone (HAZ); and one adjustable module for the wall toe and adjacent HAZ. Compliant modules are also available for weld cap inspection. The compact design keeps all sensors sited in one line across the cap, which means data can be aligned without using an encoder and scans can be made close to obstructions. The flexible, larger probe design enables the inspection of fillet welds of any size between 10mm and 25mm wide; using two separate modules offset from one another along the weld. The probe sensors are housed in a wheel-mounted support frame, with an encoder. Handle attachments are also available to aid the “walking” operator to push the probe along the weld.


The ACFM® technique has received approvals from various organizations, including DNV, Bureau Veritas, Lloyds Register, and ABS. Standard practice documents covering ACFM® have been issued by ASTM (E2261-03), ASME V, and COFREND. Training schemes are available under CSWIP, PCN, and ASNT.

ACFM Bridges Inspection

Bridges are a key feature of any country’s infrastructure with many being designed with a minimum life span of 50 years. The “life of a bridge” can be extended past it’s intended lifespan using inspection, maintenance and preservation measures. A large portion of bridge structures, particularly older ones and those carrying railway lines, are often constructed from steel I-beams or box section girders which are bolted or welded together. Such steelwork is then generally painted to help prevent corrosion. The presence of paint or rust, together with difficult access, often present challenging scenarios making inspection very difficult or time-consuming for conventional NDT techniques.

ACFM® is an NDT method developed for the detection and sizing of surface breaking defects and is particularly suited for fatigue cracks in and around welds on painted, coated or corroded surfaces because it does not require removal of the coating.

Using ACFM® as an inspection method can greatly speed up inspection, reduce waste and save time compared to other NDT techniques such as Magnetic Particle inspection. When using ACFM® it is possible to separate the roles of a local probe operator and NDT inspector; allowing use of rope access technicians to deploy probes in areas of difficult access. As a result this can avoid the need for scaffolding or other support structure, which in turn can cause closures of roads or railways under and around the bridge.

In terms of “defect data”, ACFM® provides accurate length and depth information on the size of any defect found, allowing repair efforts to be concentrated on the most serious defects, without wasting time on insignificant ones.

Portable ACFM® Inspection Technology

TSC’s portable ACFM® solution, PACE™, delivers all the functionality and benefits of Alternating Current Field Measurement (ACFM®) NDT inspection technology in a lightweight, handheld, and rugged instrument, complemented by the innovative probe design - SENSU™. Engineered to provide operators with a robust, single-user ACFM® instrument, PACE™ boasts ergonomic design features for effortless operation, catering to both left and right-handed users. The device features a large, high-contrast, strengthened LCD screen ideal for sunlight viewing and is sealed to IP65 standards, ensuring durability in harsh environments. With extended battery life, PACE™ serves as the go-to on-site inspection solution for topside crack detection. Enhanced software facilitates the creation and delivery of detailed inspection reports, including defect sizes, locations, and scans. The onboard camera enhances reports by offering detailed imagery from the inspection site, while comprehensive records of all scan data are stored for audit tracking. ACFM® desktop software supports further analysis of scan and inspection data, enabling bespoke report generation. USB 3.0 connections, along with standard VGA output, ensure simple and flexible data communication.

  • Reliable and repeatable crack detection using ACFM®.
  • Accurate defect sizing, including length and depth.
  • Capability for inspection through coatings.
  • No cleaning required; eliminates the need for in-situ calibration.
  • Integrated, portable, and robust unit with IP65 rating.
  • Long battery life of 8+ hours.
  • Toughened, high-contrast LCD screen for optimal visibility.
  • Desktop & in-car charger.
  • Built-in camera, for on-site images.
  • 4 secure corner harness points.
  • Glove accessible features.
  • Interface design enables single-handed operation during inspection (left or right).

SENSU™ Probes TSC’s functional design philosophy continues in the new and innovative probe range SENSU™. These pencil style ACFM probes, with a straight nose and right angle nose, have been designed to perform easy, continuous scanning whilst being able to gain access to challenging tight angle inspection areas. As“intelligent” probes, the SENSU™ range stores configuration information and provides instant feedback of scanning status whilst in use.

Ready to streamline your inspection process? Contact us now to learn more about our ACFM® inspection solutions, schedule a demonstration, and experience the difference in inspection efficiency and accuracy firsthand.

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