Remote Field Eddy Current Testing (RFT) Technology

PICA offers a wide range of Remote Field Eddy Current Testing (RFT) tools to inspect metallic pipes for corrosion through internal liners and scale in its Advanced NDT Service Solutions offering. The technique is ideally suited to inspect pipes with internal liners (such as cement mortar, HDPE, coal tar epoxy, and other liners), but it can also be deployed on unlined pipes. Properly implemented RFT employs many detectors (sometimes hundreds) around the circumference to create detailed corrosion maps of the metal cylinder. The technique is well suited for cast iron pipe, ductile iron pipe, steel pipe, concrete cylinder (bar-wrapped) pipe, reinforced concrete cylinder pipe, and prestressed concrete cylinder pipe (PCCP).  Detailed mapping of the cylinder also provides insight on the construction style (e.g., spiral welded vs. seam welded) and cylinder stresses, in addition to both internal and external localized corrosion.  It is called “remote field” because the exciter and detectors are spaced at least 2.5 pipe diameters apart. PICA’s remote field tool models have various names pending their application – SeeSnake, HydraSnake, Chimera, EMIT & RAFT


  • RFT is used in all industries served by PICA (water, wastewater, power, industrial, mining, and oil & gas).
  • RFT is designed to be used on all metallic pipes, including nodular materials such as cast and ductile iron.
  • RFT is also successfully used to inspect concrete pressure pipes containing a steel cylinder, such as C303 bar-wrapped (concrete cylinder) pipe, PCCP, and reinforce concrete cylinder pipe.
  • Free-swimming RFT tools can be launched in fully operational pipes up to 42-inch diameter.
  • RFT tools for dewatered applications in pipe sizes from 36-inch to 84-inch are winched between access openings.

Large Diameter (36-inch to 84-inch)

RFT 36 inch to 84 inch 1 scaled 1
RFT 36 inch to 84 inch 2 scaled 1


  • PICA’s RFT tools effectively locate and quantify cylinder corrosion in metallic pipe (cast iron, ductile iron, steel) and concrete pressure pipes containing a steel cylinder (PCCP, bar-wrapped pipe, and reinforced concrete cylinder pipe).
  • PICA’s RFT is a non-contact non-destructive testing method; internal liners, scale, mud, or sand will not interfere significantly with the operation of the tool or inspection results.
  • High-resolution wall loss measurements are collected every 0.1-inch axially and up to 2-inches circumferentially, allowing both axial and circumferential location reporting.
  • Minimum volume of reported wall loss = 1.4-inch x 1.4-inch x 30% deep wall loss (or equivalent volume) in the metallic cylinder.
  • RFT has equal sensitivity to external and internal wall loss and will detect metal wall loss even when it is located on the far side of the cylinder.
  • PICA’s RFT tools do not cling to the pipe wall and are suspended on smooth-rolling soft urethane wheels; therefore, the tool will not damage internal liners.
  • Although the RFT tool is not calibrated to measure corrosion at double joints, additional data points at the joints help accurately flag joints that are different from most of the joint population.
  • For PCCP and bar-wrapped pipe, RFT provides information on the compressive force on the steel cylinder exerted by the prestressing wires or post-tension bars.
  • RFT can be used to detect broken wires in embedded cylinder PCCP along with “loss of preload,” if present.
  • For PCCP with hydrogen embrittled wires, RFT helps identify if the embrittlement breaks are affecting the pressure capacity of the pipe.
  • Tool components are modular and can fit through 18-inch access manway openings.
    RFT 36 inch to 84 inch 2 scaled 1
    RFT Mid Size 30 inch 2 scaled 1

    Mid-Size (16-inch to 36-inch)


    • Articulated mechanical design provides flexibility to navigate elbows.
    • The diameter of each tool is slightly smaller than the internal diameter of the pipe to allow for protrusions, lining, and scale.  Centralizers maintain a uniform annulus between the tool and the pipe.
    • Size-on-size access is required for tool insertion and retrieval.
    • Depending on tool size and access availability, the tools can be directly loaded into the pipeline through a manhole, through a removed section of pipe, or through a launch barrel.
    • If a tool can be deployed in free-swimming mode, it can travel long distances between access points.
    • In dewatered pipe, tools can be tethered on both ends and winched through pipeline sections up to 6,000 feet.
    RFT Small Diameter 12 inch 2 scaled

    Small Diameter (2-inch to 16-inch)


        • Capable of providing high-resolution pipe wall thickness measurements.
        • Detects internal and external areas of wall loss, graphitic corrosion, cracks, or local stress concentrations (e.g., dents) in metallic pipes.
        • Can scan through liners without damaging them.
        • Can be deployed in either free-swimming or tethered mode.
        • Battery life is 100 hours, so free-swimming inspections can be long-range, e.g., over 30 miles in length.
    RFT Small Diameter 12 inch 2 scaled