Modernizing Subsea ACFM


  • Bringing high-quality True ACFM inspection data to the surface

  • Accurate crack detection and sizing technology

    Owner of previous version? Read this important EOL notice

    Watch the Webinar

    The webinar features a demonstration where Dr. Michael Smith shows you how the U41 true ACFM subsea inspection system delivers accurate subsea crack detection and sizing, better data quality with new electronics, faster inspection with easier deployment, array probes and reporting.

    The webinar will include:

    • An introduction to the U41
    • An overview of the main features and applications
    • A demonstration of system
    • Q&A


    Dr Smith U41 Webinar

    Dr Michael Smith

    Watch Webinar Now

    A diver or ROV deployable ACFM® subsea inspection system for the detection and sizing of surface-breaking cracks.

    For the last 30 years, ACFM® technology has been used globally as the method of choice for the detection and sizing of subsea surface-breaking cracks. Recognized and approved by many certification bodies, including DNV, ABS and Lloyds, the technique has been used successfully against traditional uncomputerized and more user dependent methods, such as MPI.

    As today’s industry is looking to scale the use of auditable NDT methods to all their assets, faster, more flexible, easier to deploy inspections and better reporting capabilities are required. Who else but Eddyfi Technologies to redefine and modernize subsea surface crack inspection with its new TSC U41.

    The TSC U41 is supported by a global network of calibration and training centres, located in Milton Keynes (UK), Québec (Canada), Houston (USA) and Dubai (UAE).


    • Structural node welds on jackets
    • Caisson inspection
    • Pipeline damage
    • Spudcans
    • Welded plate structures
    • Mooring systems including chains

    U41 Features and Benefits

    Faster inspections

    • Connect 3 probes simultaneously to avoid frequent returns to the surface, thus saving time.
    • 10 x faster acquisition electronics, improving scanning capabilities and inspection integrity.
    • Diver mini-array probe and ROV full-array probes reduces the number of scans and allows for faster recognition and characterization of defects.
    • Reduced cleaning requirements, no need to clean to bare metal.

    Improved data quality

    • Increased ACFM signal quality with 14x increase in data resolution, improving the accuracy of data acquisition with the better ability to zoom on acquired signals.
    • Probe calibration files are saved on the probe instead of a remote PC. This removes the potential for incorrect probe calibration being used.
    • Lower noise increases the signal-to-noise ratio, inspect through coatings twice as thick compared to previous model
    • Capable of inspecting corroded surfaces or through non-conducting coatings several millimeters thick.

    Easier to use

    • New Assist3 reporting software version, with a simpler and more modern interface, and with continuous evolution.
    • Umbilical reel dramatically reduced in size: 1/3 less weight and 1/3 less storage. Up to 3 umbilicals can be connected for a total length of 450 m.
    • Easy to configure communications with support for multiple protocols to ROVs (Ethernet, Extended Ethernet, RS232, RS485).
    • Global network of service centers
    ACFM ASSIST Software



    Deployment Methods

    The following are ways that ACFM is envisaged to be deployed subsea:

    Diver from fixed platform, vessel or from saturation bell (U41D / U41DA)

    The subsea bottle is lowered to the diver and the diver uses probes connected to the bottle through a 5m cable. There is an umbilical cable from the bottle to a topside unit that provides power and communication to the bottle. The umbilical is 150m standard with subsea connectors at both ends. Three umbilicals may be connected together for a total length of 450m. A 15m whip is provided between the top umbilical and the topside unit so that this can be temporarily fixed-routed to the dive shack (normal ACFM operator location). The diver uses simple Bx/Bz pair probes or the mini (8 channel) array (requires the DA version).

    U41 Diver deployment
    U41 MagCrawler deployment

    Crawler deployed from basket (U41R)

    A remote crawler is used to inspect a weld or section of parent plate using a swept array probe. The crawler is placed in a basket with the bottle and joined via a long probe cable (up to 50m may be required). This is lowered over the side of a vessel or platform.

    The crawler is taken out of the basket by an ROV which then places it near the work zone. The bottle is connected to the surface by its own umbilical (similar to the diver situation) and there is no electrical interface between the bottle and ROV.

    Scanner used with ROV (U41R / U41RDW)

    A scanned array probe is fitted to a custom scanner which is itself deployed to the inspection site by a ROV. The bottle is integrated onto the ROV skid with a long umbilical to the probe (up to 50m required). A short whip is used to wire the bottle to the ROV electrical system through which the bottle receives power and comms. The ROV can have various comms protocols depending on the age and type of ROV. This can be RS232, RS485 (2-wire), RS485 (4-wire) or Ethernet. Whilst there is a move towards newer ROVs supporting Ethernet, there are still many ROVs that only have the older serial protocol facilities.

    ACFM ROV Crawler
    ACFM Subsea ROV deployment

    Pick-and-place array deployed directly from ROV manipulator (U41R / U41RDW)

    The connections are the same as the above however the probe is placed directly on a weld by the manipulator and held in place briefly while a short linear array of coils is read. The probe is then moved along the weld to a new place (ensuring some overlap with the previous placement) and another set of readings taken. The weld is therefore inspected in short sections that may be joined together.



    Find out more about TSC U41 , book a demo or simply stay up-to-date.

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    3 x SENSU2 UW

    Max umbilical length

    • U41D \ DA: 450 m (1476 ft) (Extended Ethernet)
    • U41R \ RDW: 450 m (1476 ft) (Extended Ethernet)1

    (Standard length 150m, up to 3 can be connected in series)

    1. otherwise limited to ROV umbilical length


    • U41D: No
    • U41DA: 4 x rows mini
    • U41R / RDW: Up to 32 x rows


    • U41D / DA: Extended Ethernet only
    • U41R / RDW: Ethernet/Extended Ethernet/RS485/RS232

    Depth rating

    • U41D / DA / R: 300 m (984 ft)
    • U41RDW: 2000 m (6561 ft)

    Topside Units Type

    • U41D / DA: Topside Unit D
    • U41R / RDW: Topside Unit R

    Bottle dimension

    • U41D / DA / R: 156 x 156 x 430 mm (6.2 x 6.2 x 17 in)
    • U41D / DA / R: 156 x 156 x 292 mm (6.2 x 6.2 x 11.5 in) (without lifting cage)
    • U41RDW: Contact Us

    Bottle weight (in air)

    • U41D / DA / R: 9.2kg (20.3lb)
    • U41RDW: Contact Us


    • U41D: Single
    • U41DA: Dual
    • U41R / RDW: Multiple

    Operating temperature range

    0–45°C (32–113°F)

    Probe cable length

    5m (16ft)

    Power requirements

    Topside: 110 V AC / 400 mA U41: 48 Vdc / 1A

    Read this important notice about previous version of product: U31