NDT – Conventional

Oceaneering provide highly skilled, experienced and motivated personnel qualified and certified in accordance with international certification schemes (e.g. PCN (EN 473/ IS0 9712), ANSI CP-189 and SNT-TC 1A) in the conventional techniques that have underpinned the NDT industry from its earliest days.

Dye Penetrant Inspection (PT)
A low cost method of detecting surface breaking flaws, such as cracks, cold laps, porosity etc. The dye penetrant is drawn into the surface breaking flaw by capillary action and excess surface penetrant is then removed; a developer is then applied to the surface, to draw out the penetrant in the crack and produce a surface indication. The technique can be applied to any non-porous clean material, metallic or non-metallic, but is unsuitable for dirty or very rough surfaces.

Eddy Current Inspection (ET)
An electrical technique detecting surface breaking defects in all electrically conducting materials through paint and surface coatings. All electrical methods are indirect; a material property is measured as an electrical property variation. A coil carrying an AC current is placed on the specimen surface. This generates circulating eddy currents in the specimen close to the surface and these in turn affect the current in the coil by mutual induction. Flaws and material variations affect the strength of the eddy currents. The presence of flaws is therefore measured by electrical changes in the excitation coil. Applications range from crack detection to metal sorting and from tube, bar and weld inspection.

Magnetic Particle Inspection (MT)
An extremely cost effective method for the detection of surface and near surface flaws in ferromagnetic materials is primarily used for crack detection. Following magnetisation the specimen is covered with very fine iron particles either dry or suspended in a liquid. Surface breaking flaws distort the magnetic field causing local magnetic flux leakage that attract the iron particles producing a build-up that can be seen visually.

Ultrasonic Inspection (UT)
Ultrasonic methods of NDT use beams of mechanical waves (vibrations) of short wavelength and high frequency, transmitted from a small probe in contact with the specimen surface and detected by the same or other probes. Such mechanical vibrations have different forms depending on the direction of particle movement in the wave motion, so there are several forms of ultrasonic waves. The most common and widely used in NDT are compressional and transverse (shear) waves. They can travel large distances in fine-grain metal and an oscilloscope display (A-scan) shows the time that it takes for an ultrasonic pulse to travel to a reflector (flaw or back-surface). Applications include location of manufacturing defects in welds and castings through to Corrosion / Erosion monitoring and large scale corrosion mapping.

Radiographic Inspection (RT)
A well established NDT technique which uses gamma-rays or X-rays to produce the image of an object onto film. The source of radiation is either an X-ray tube, which is normally described by the electrical voltage across the X-ray tube with the higher the voltage the higher the penetrating power of the radiation or a pellet of radioactive material emitting gamma-rays: Iridium 192, Cobalt 60, Selenium 75, Ytterbium 169. Applications include wall loss detection and sizing in pipes and plate through to manufacturing defects in welds, forgings castings etc.

Radiography provides a quality, cost effective, permanent record with high volume capabilities due to simple operation and portability. However, its use is restricted by the inherent risks associated with the use of radiation and the need to establish and manage a controlled area during the process. The associated problems are greatly reduced by the use of the ‘Small Controlled Area Radiography’ (SCAR) system, developed by Oceaneering. SCAR has set the precedent for safer working in the industry.

The SCAR system-Innovation in NDT
Radiography is a well-established conventional NDT technique with inherent risks associated with the use of radiation. Managing the safety risk by the setting of ‘controlled areas’ has the adverse affect of reducing clients’ production time. It was this clear market pull that triggered the innovative capability of Oceaneering to develop the ‘Small Controlled Area Radiography’ (SCAR) system. The system enables radiography to be performed in the heart of the workplace without disruption to normal operations.

The SCAR system comprises an internationally certified, purpose built, BS EN 3999 Category X gamma radiation source camera. The improved shielding and beam collimation provided by the camera allows the source exposure to be done more simply to the required standard of radiation protection. The gamma camera is pneumatically actuated from a remote distance, has a ‘fail-safe’ built in safety feature and automatically terminates exposures from a unique timer on the control box.

“Baby SCAR” the latest development was inspired by Oceaneering and the Sentinel model 959, undoubtedly the safest gamma radiographic system in the world. The ‘’baby SCAR’’ provides the same ultra-safe, non-projection feature as the original. The model 989 is fully ISO 3999 approved as category ‘X’ and Type ‘A’ package, rated to carry a 740 GBq (20 Curie) Selenium 75 payload. It has a Tungsten primary shield with a 40º square directional beamport and only weighs 7.5kg meaning it is incredibly easy to position using the Oceaneering purpose built clamping mechanism. Simple actuation pushes the isotope from the stored position to the open position using a conventional Sentinel Teleflex cable mechanism, using only a quarter turn on the handle to expose and retract, with a “posilok” safety locking mechanism.