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EMT

Tube Testing

TÜV AUSTRIA Belgium offers a complete range of state-of-the-art tube testing technologies to asses the integrity of installed heat exchangers, steam generators, boilers, air conditioners, coolers and condensers. Inspection and upgrading of new tubes can also be considered, and this according international standards as ASME and ISO. Most of the technologies are based on electromagnetic principles for fast and precise inspection, and some of them use ultrasonic and acoustic waves for quantitative measurements.

Next tube testing technologies are standardly proposed:

Following technologies can be proposed on special demand:

  • Eddy Current Array (ECA)
  • Near Field Array (NFA)
  • Acoustic Pulse Reflectometry (APR)

Choice of technology will depend on the heat exchangers configuration and expected degradation phenomena. See Table 1 for suitability according to tube material and characteristics. See also Table 2 for a summary of each technology’s capabilities and main characteristics.

ECTT (Eddy Current Tube Testing)

ECTT using bobbin probes is commonly used for inspection of condensers, coolers, steam generators and heat exchanger tubes. It is a very fast and sensitive electromagnetic testing technique for inspection of non-ferromagnetic materials. Eddy Current are induced in the tubes by an alternating magnetic field generated from de probe. Flaws will interact with the induced current and returning a different magnetic field to the probe. This variation is translated to changes in impedances measured by an instrument.

TÜV AUSTRIA proposes in-situ examination and inspection of new tubes according ISO and ASME standards. Our inspection procedures use multifrequency technology with mixing channels to surpass all inspection standards. Approximately 400 to 600 tubes (6m long) can be inspected in one normal working day. All data is saved, and a report is generated the same day.

FSEC (Full Saturation Eddy Current)

FSEC Tube Testing is used for inspection of low ferromagnetic tubes such as Duplex steel. The technique is identical to ECTT using bobbin probes. Whit the difference, that probes are mounted with permanent magnets to saturate tube wall to bring back the relative permeability close to that of a non-ferromagnetic tube material. FSEC is a very fast and sensitive electromagnetic testing technique with the same detection and sizing capabilities as ECTT.

TÜV AUSTRIA proposes in-situ examination and inspection of new tubes according ISO and ASME standards. Our inspection procedures use multifrequency technology with mixing channels to surpass all inspection standards. Approximately 350 tubes (6m long) can be inspected in one normal working day. All data is saved, and a report is generated the same day.

IRIS (Internal Rotating Inspection System)

IRIS tube testing is a well-known wall thickness measurement technique for heat exchanger tubes. IRIS is basically an Ultrasonic Testing (UT) technique for thickness measurements under immersion. Ultrasonic beams are reflected against a rotating mirror to measure remaining tube thickness. To do so, tubes must be filled with water for UT transmission. Continuous water supply is needed to flood the tubes and to rotate the mirror mounted on the IRIS probe. This way it is possible to measure wall thickness of a tube for over all its length and circumference.

TÜV AUSTRIA is using the state-of-the-art IRIS inspection solution from EddyFi. Each tube data is saved and can be displayed as C-Scan (a 2D deployed view of the tubes) for precise wall loss localization. IRIS can be used on ferro-and non-ferromagnetic materials and is often used as a secondary tube testing technique or back-up to the much faster electromagnetic inspection techniques such as ECTT, RFT, NFT and MFL.

MFL (Magnetic Flux Leakage)

MFL is a tube testing technique for inspection of finned ferromagnetic tubes where internal pitting is expected. It is very fast and has a good circular crack detection capability. MFL is an electromagnetic testing technique that magnetizes tube wall using permanent magnets installed in the probe. When a flaw is present, a magnetic flux leaks out the saturated wall thickness and is sensed the probe.

TÜV AUSTRIA proposes in-situ examination. Approximately 350, 6-meter-long tubes can be inspected in one normal working day. As secondary technique, IRIS or endoscopy are mostly proposed. All data is saved, and a report is generated the same day. An alternative technique for inspection of finned tubes is NFT. Less sensitive to external defects, but better in flaw depth evaluation.

NFT (Near Field Testing)

NFT is a tube testing technique for inspection of finned ferromagnetic tubes where internal pitting corrosion and erosion are expected. NFT is an electromagnetic through transmission technique like RFT. With the advantage that it isn’t affected by baffle plates now the sensing coils are put in the near field of the transmitting coil of the probe.

TÜV AUSTRIA proposes in-situ examination according ASME standards. Approximately 250, 6-meter-long tubes can be inspected in one normal working day. As secondary technique, IRIS or endoscopy are mostly proposed. All data is saved, and a report is generated the same day. An alternative technique for inspection of finned ferromagnetic tubes is MFL. MFL is less accurate in flaw depth evaluation, but a little more sensitive.

PSEC (Partial Saturation Eddy Current)

PSEC or magnetic bias eddy current tube testing is like RFT used for inspection of ferromagnetic heat exchanger and boiler tubes. The technology is based on ECTT. Whit the difference that PSEC probes are mounted with electromagnets powered by a DC generator to saturate tube wall. This brings back the relative permeability close to that of a non-ferromagnetic tube material. PSEC is a very fast and sensitive electromagnetic testing technique with detection capabilities close to ECTT. It is more sensitive to small pitting than RFT, but less appropriate for general wall loss detection and depth evaluation.

TÜV AUSTRIA proposes in-situ examination according ISO and ASME standards. Approximately 350, 6-meter-long tubes can be inspected in one normal working day. As secondary technique, IRIS or endoscopy are mostly proposed. All data is saved, and a report is generated the same day.

RFT (Remote Field Testing)

RFT is a useful tube testing technique for inspection of ferromagnetic heat exchanger and boiler tubes. It has excellent sizing capabilities and perfectly applicable for erosion and corrosion examination. RFT is an electromagnetic through transmission technique, where sensors are detecting variations of the eddy currents induced in the far field of the transmitting coil of the probe.

It is slightly less sensitive than ECTT and can’t differentiate in- and outside defects. As alternative PSEC can be proposed when small pitting indications are expected or when baffle erosion is expected. Although it is the most appropriate electromagnetic testing solution for wall loss evaluation of thick carbon steel tubes.

 

TÜV AUSTRIA proposes in-situ examination according ASME standards. Approximately 250, 6-meter-long tubes can be inspected in one normal working day. As secondary technique, IRIS or endoscopy are mostly proposed. All data is saved, and a report is generated the same day.

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