TechCorr utilizes five techniques to perform tubular testing on heat exchangers, air coolers, boilers, and other tubular devices. Four of the techniques are Electromagnetic based techniques (ET), andthe last technique is IRIS an Ultrasonic Technique (UT). We also use Long Range Ultrasonic Technique (LRUT) for heater tube inspection. Having all five techniques at our disposal makes our Tubular Division a diversified inspection group. Being this diversified can help meet the needs of our customers and enables each crew with the capability to perform the correct inspections providing the most comprehensive services possible.
IRIS is one of the most recognizable inspection methods. It was originally developed for Air Cooler inspections. The method operates by utilizing a unique water driven rotating mirror to direct an ultrasonic beam, which is reflected 90 degrees to the internal tube wall. The ultrasonic transducer is mounted axially in the tube and the ultrasonic beam is directed toward the mirror, which is placed at a 45-degree angle to the transducer. Using special ultrasonic electronics and computer a B-scan and/or C-scan image is presented.IRIS is an extremely accurate (plus or minus 3%) examination but is limited in the size of the discontinuity it can detect. Cracks are normall€y not found during the examination while pitting, general wall thinning and fretting are normally identified and measured.
Eddy Current Testing is the most commonly used method, but is limited to non-ferromagnetic and slightly magnetic alloys. The Eddy Current technique is based on the induction of an electromagnetic field in the component being examined and can detect various forms of internal and external damage. The inspection consists of a full-length examination performed on the inside of the tube with equal inner and outer surface discontinuity detection and sizing. The purpose of this application is to detect I.D. and O.D. degradation such as cracking, corrosion, erosion, pitting, fretting and gradual wall loss generally found in non-ferromagnetic tubing.
The Remote Field Technique is an electromagnetic examination, which utilizes a through-transmission process. The resultant field is affected by either ID or OD tube wall anomalies. RFT signal measurements are made a few tube diameters away from the AC excitation coil without any attempt at tube wall magnetization or saturation.
The Near Field Testing (NFT) is intended specifically for fin fan carbon steel tubing inspection without the requirement for externally referenced coils. This technology relies on a simple driver-pickup eddy current probe designed to provide very simple signals for analysis.
NFT probes are specifically designed to detect internal corrosion, erosion, or pitting on the ID of carbon steel tubing. These probes actually measure the lift-off or “fill factor” and convert it to amplitude-based signals.