Rotating Probe

A rotating probe (also called RPC or motorized rotating pancake coil) is an eddy current probe with one or more pancake coils mounted on a rotating head, used inside tubes to detect circumferentially-localized defects that bobbin probes cannot characterize.

Definition

RPCs spin at 600–3000 rpm while being pulled axially, mapping the tube ID like a C-scan. They detect axially-oriented cracks, pitting at U-bends, and tube-to-tubesheet weld defects that escape bobbin inspection.

Related terms

  • Bobbin Coil — A bobbin coil is a differential or absolute eddy current probe that travels axially inside a tube, inspecting the entire tube circumference simultaneously for wall loss, pitting, and through-wall defects.
  • Multi-Frequency Eddy Current — Multi-frequency eddy current testing uses two or more simultaneous frequencies whose responses are mixed in software to suppress unwanted variables (support-plate signals, tube-end effects) and isolate the defect signal of interest.
  • Internal Rotary Inspection System (IRIS) — IRIS is an ultrasonic tube-inspection technique in which a water-driven rotating mirror inside the tube directs an ultrasonic beam radially outward, producing a high-resolution image of wall thickness and ID/OD pitting.

Further reading

heat exchanger tube inspection methods procedures

More equipment terms

Calibration Block · Transducer · Dual-Element Probe · Angle-Beam Probe · Normal-Beam Probe · Couplant · Reference Reflector · Side-Drilled Hole · Flat-Bottom Hole · Notch Reference

Where this comes up in practice

Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.

Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.