RFT inspection tools provide an improved probability of detection (P.O.D.) and exceptional accuracy for sizing of corrosion pits and internal and external damage for pipelines lined with cement, epoxy or polyethylene. Tools that use Magnetic Flux Leakage (MFL) require intimate contact with the pipe wall in order to achieve acceptable flaw sizing and are not compatible for use with lined pipelines.

Dacon’s RFT Pipeline Inspection tools requires no contact with the pipe wall, and can measure through scale, wax and non-magnetic liners such as concrete, epoxy or polyethylene. Dacon’s RFT Pigging tools have a minimum clearance of 0.250″ (6.3mm) to allow passage of the tool past weld roots, dents and internal deposits and are very well suited for testing of concrete lined pipelines. Using Remote Field Test principles the tool is able to detect internal and external defects.

RFT technology works by detecting changes in an AC electromagnetic field generated by the tool. As the field passes through the pipe wall it is attenuated and delayed (it becomes stronger in areas of metal loss and the time delay is less). The field interactions are measured by on board detectors, and subsequently processed on the tool itself using A/D converters and DSPs. Once all the data is acquired, sophisticated analysis software is applied to generate accurate information on the wall thickness of the line. Figure 1 (below) schematically shows the magnetic coupling path between the exciter section of the tool and the detector array.

Advantages of RFT Technology for In-Line Inspection Tools:

  • Equal sensitivity to ID and OD pits, erosion and cracks
  • Minimal pre-cleaning required: works through liners, scale and other deposits
  • Needs no couplant, can be pushed with any medium (water is preferred for good speed control)
  • No magnetic attraction to pipe, so very little differential pressure needed for propulsion
  • Does not have sensors in contact with the pipe, so no damage to epoxy or cement liners
  • Plenty of clearance (up to 2″, 50mm) for good cornering ability
  • Low flow and other un-piggable lines are our specialty