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SLOFEC – Tank Inspection Services

SLOFEC – Tank Inspection Services

Reliable SLOFEC Inspection Method for Your Tank

Corrosion can cause severe damage to tanks, pipes and boiler tubes, have costly consequences for plant owners, render risks of pollution for the environment and presents safety hazards for operators. Because of all the risks involved, corrosion damage must be prevented or detected at early stages in order to avoid halt of production or unforseen incidents.

SLOFEC is a reliable non-destructive testing method for tank inspection as well as tank floor, roof, wall, boiler tube and pipe inspection. SLOFEC tank inspection is a trademark acronymn for “saturated low frequency eddy current”. In contrast to ultrasonic inspection SLOFEC does not require liquid coupling and coatings of up to 9mm thickness must not be removed for the inspection. SLOFEC is one of the most reliable ways to detect small cracks and pitting and general corrosion on a material flat or curved surfaces, while distinguishing where that anomaly (inner diameter or outer diameter) really is.

Numerous years of extensive experience in conventional and advanced non-destructive testing methods and the exclusive training of our experts in the SLOFEC tank inspection technique enable TÜV Rheinland to help you localize corrosion in your tanks fast and reliably and to support you in finding solid solutions. Our SLOFEC tank inspection services are provided through a cooperation agreement with KontrollTechnik GmbH, a German company ( ), specialized in eddy-current inspection services. A licensed partner using KontrollTechnik GmbH’s technology, TÜV Rheinland experts have received specific training to conduct SLOFEC tank inspection services. All to provide you with the most reliable and precise inspection services for your vessels.

Benefits of Our SLOFEC Tank Inspection Services at aGlance

The SLOFEC tank inspection services can offer you:

  • A reliable inspection and corrosion monitoring method for thick-walled storage tanks.
  • High detection capacity for small defects and local top- and bottom-side corrosion.
  • A clear,colored corrosion mapping report of the detected damages.
  • Fast inspection times and high-speed results.
  • The exclusive SLOFEC c-scan reporting software.
  • A method applicable to ferromagnetic as well as non-ferromagnetic materials.
  • Possible testing through non-conductive coatings.
  • Comprehensive advanced NDT services from a single source.

Please feel free to contact us at TÜV Rheinlandto learn more about how our SLOFEC tank inspection services can benefit your company.

Our SLOFEC Tank Inspection Approach

The SLOFEC tank inspection technique has proven its reputation in the field of advanced non-destructive testing, as a high-speed and reliable method to detect local corrosion in storage tanks.It is recognized as one of the leading technologies to deliver high quality defect and corrosion mapping reports upon inspection of diverse vessels such as pipelines, boiler tubes or tanks. The SLOFEC approach is a valued NDT technique within the oil and gas industry, as it presents the advantage of the capability to conduct testing and inspection on both ferromagnetic and non-ferromagnetic materials.

Our saturated low frequency eddy current (SLOFEC) inspection services are conducted with pipe scanners as well as flat scanners and enable examination of both internal and external tank surfaces. The scanner has the capacity to conduct inspections on a wide range of thick-walled and/or coated storage tanks, be it floors, walls or roofs. The modular design of the scanner allows SLOEC scanning equipment to quickly adapt to any surface being inspected. During tank inspection, a TÜV Rheinland testing operator manually moves the scanning device over the tested equipment’s surface and signal data are directly recorded in the reporting and analysis computed system, permitting defects and corrosion spaces to be displayed and analyzed online.

The SLOFEC tank and pipe inspection technique combines the eddy-current principle and a magnetic field, increasing the testable penetration depth of wall thickness. Because it is possible to adapt the eddy-current frequency to each tested material, our experts can use the SLOFEC method to inspect a wide range of vessels of different wall thicknesses as well as coated equipments.

Upon completion of the tank assessment or tank floor inspection, eddy-current signals are color coded to provide you a clear and user-friendly defects and corrosion mapping. The color system not only offers a clear overview of the defects, but also provides detailed information on the condition and severity status of every single growing fault within the equipment. This report enables our TÜV Rheinland experts to advise clients on corrective actions and targeted maintenance for the inspected material.

SLOFEC Application Range

Our saturated low frequency eddy current inspection services can be applied to:

  • Pipe inspection
  • Boiler tube testing
  • Tank roof, wall and floor corrosion mapping
  • Spheres and cisterns
  • Thick-walled tanks up to 22 mm
  • Top-side and bottom-side corrosion
  • Steel, carbon steel and non-ferromagnetic materials
  • Corrosion detection in walls and coatings

SLOFEC Inspection vs Magnetic Flux Leakage (MFL) Technique

Because the SLOFEC method has an electromagnetic technical background, it is often compared to the Magnetic Flux Leakage (MFL)technique.

The MFL technique is a non-destructive testing method for corrosion detection and surface discontinuities in storage tanks, pipelines and other ferrous materials. MFL magnetizes steel with a strong magnet and corrosion or defects are detected through areas of magnetic leakage within the tested steel.

But, the SLOFEC inspection technique presents numerous advantages over MFL:

  • SLOFEC can be applied to thicker walls and surfaces with coatings.
  • It has a higher and more precise detection capacity.
  • It can be used for both top- and bottom-side surfaces.
  • It can be applied to non-ferromagnetic materials.

However, SLOFEC tank inspection, an electromagnetic-based testing method, is not used for absolute wall thickness measurement, but rather as a comparison technique. This implies that tested material properties need to be determined before conducting a SLOFEC inspection.


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