Facebook Linkedin Instagram
  • 0

    • Non Destructive Testing (NDT) Equipment and Tools

    Non Destructive Testing – Underwater NDT Equipment

    Non-destructive testing (NDT) equipment is essential in commercial diving for assessing the integrity of subsea structures and equipment without causing damage. The primary goal of underwater NDT equipment is to identify flaws, defects, corrosion, or cracks that could impact safety and functionality. These methods include techniques like ultrasonic testing, magnetic particle testing, and eddy current testing, each suited for different materials and conditions.

    NDT equipment is also used to measure metal thickness and other critical parameters, supporting accurate inspection and monitoring routines. NDT is crucial not only for detecting existing issues but also for predictive maintenance, helping to prevent major problems and ensuring the continuous safe operation of underwater installations. This makes underwater NDT equipment a vital tool for maintaining the longevity and reliability of essential measurement operations on underwater structures.

    Product categories
    Filter By Brand
    Filter By Type

    Frequently Asked Questions

    A Multiple Echo Ultrasonic Thickness Gauge, such as those manufactured by Cygnus, is a critical tool for monitoring corrosion on ship hulls and subsea pipelines. The probe emits a high-frequency sound wave into the metal. The multiple-echo technology specifically measures the time it takes for the sound wave to bounce back and forth purely within the metal wall. Crucially, this advanced method completely ignores the thickness of anti-fouling paint or protective coatings on the surface, providing the diver with a highly accurate measurement of the remaining bare metal without having to grind away the protective layer.

    Submerged steel structures naturally undergo galvanic corrosion, essentially acting like a battery in saltwater and slowly dissolving. To prevent this, engineers install sacrificial anodes (blocks of zinc or aluminium) that corrode instead of the steel, a process called Cathodic Protection (CP). A BathyCorrometer is a highly specialised, diver-held voltmeter used to measure the exact electrical potential of the structure. By pressing the probe against the steel, the NDT diver can instantly verify if the sacrificial anodes are still actively protecting the asset, or if they have depleted and require urgent replacement.

    Offshore oil and gas platforms are typically supported by massive steel jackets made of hollow, sealed tubes (members). If a microscopic stress crack develops, the immense pressure of the ocean will force water inside, flooding the tube. Flooded Member Detection (FMD) systems use either ultrasonic or gamma-ray technology to scan the outside of these tubes. If the system detects water inside a tube that is designed to be full of air, it immediately alerts the engineers to a hidden, potentially catastrophic structural failure that cannot be seen with the naked eye.

    While ultrasonic gauges measure overall thickness, Magnetic Particle Inspection (MPI) is used to detect microscopic surface and near-surface cracks in critical load-bearing welds. The NDT diver uses a heavy-duty subsea electromagnet (a yoke) to induce a strong magnetic field across the weld. They then spray fluorescent, magnetic iron particles into the water. If there is a microscopic crack, it disrupts the magnetic field, drawing the glowing particles directly into the flaw. When illuminated with an ultraviolet (UV) dive light, the crack shines brilliantly, allowing the diver to photograph and accurately measure the defect.

    Because NDT equipment is used to legally certify the safety of multi-million-dollar offshore infrastructure, the calibration regulations are incredibly strict. Ultrasonic thickness gauges, BathyCorrometers, and MPI yokes must undergo highly documented, certified laboratory calibration at least once every 12 months. Before every single dive, the NDT inspector must perform a “function check” using a known calibration block or reference standard on the deck. If the equipment fails to read the reference block perfectly, it cannot be legally used for the subsea inspection.