The technique is used widely for weld and thread inspection and can be used sub-sea for the inspection of offshore structures. ACFM can be used on both magnetic and non-magnetic components and (with special probes) at temperatures up to 600°C.

The benefits of ACFM include: -

• Little or no surface preparation
• Rapid scanning
• Reliable and repeatable
• Accurate sizing for both length and depth.
• Hard copy results
• Portable
• Windows Compatible
• Sub-sea Application
• Can be used in conjunction with rope access removing the need for costly scaffolding operations

Alternating Current Field Measurement (ACFM) Technology using TSC Inspection System’s thread inspection probe provides a rapid and reliable method of crack detection and sizing for both the internal and external threads of a wide range of threaded components. The system is currently being applied to the inspection of drillstrings, mud motors, studs, bolts and casings. The system is field proven and is currently included in NS-2 Drill String Inspection Standard. The development of ACFM has been supported by BP, Shell, British Gas, Statoil and OSO.

The ACFM system offers a number of benefits when compared to conventional inspection methods:
• Reduced cleaning requirements.
• Suitable for magnetic and non-magnetic components.
• Provides information on crack location, length and depth.
• Reduces false calls.
• Data is stored for replay, review or for future audit.
• Windows compatible system.
• Easy transfer of electronic data.
• System can be used for inspection of other components.

ACFM probes are available to cover a wide range of common drill string connection sizes or can be tailor made for specific sizes.
ACFM does not require electrical contact with the component and can be used to inspect through coatings or scale.
The ACFM technique has been designed for the detection and sizing of surface breaking cracks on a variety of materials – Carbon Steel, Titanium, Inconel, Monel and Stainless Steel - and can be used as a substitute for magnetic particle inspection or dye-penetrant inspection, with the addition of providing information on crack depth. The sizing software is normally for use with carbon steels; however, if required, this can be adapted for use with non-magnetic steels.
The ACFM system also provides a flexible inspection capability and can be used to inspect shoulder areas, tool joints, weld areas and boxes.

In Eddy Current Inspection (ECI), an alternating current is made to flow in a coil, which in turn produces an alternating magnetic field around it. This coil, when brought within close contact to the electrically conducting surface of a metallic material to be inspected, induces an eddy current flow, parallel to the coil winding, in the material due to electromagnetic induction. The presence of a defect or discontinuity in the material disturbs the eddy current flow. These eddy currents, in turn, generate an alternating magnetic field (in the opposite direction) which can be detected either as a voltage across a second coil or by the perturbation of the impedance of the original coil.

Eddy Current Inspection can be used in the following applications: -

Surface crack detection of in-service components.
In-service inspection of ferritic welds for fatigue cracking.

Eddy Current Inspection, using the Hocking system, has the advantage that inspection can be carried out on components without the need for coating removal, saving on downtime, coating removal costs and the cost of reinstating the coating.

Ultrasonic Testing (UT), uses beams of mechanical waves (vibration) of short wavelength and high frequency tramsmitted from a probe and detected by the same or other probes. The most common technique is the pulse-echo technique, which makes use of the principle that sound waves travel in straight lines and are reflected by an obstacle in their path. This obstacle can either be a flaw within the material or the back-wall or steel-air interface.
Sound waves can be passed through solid materials and are reflected from the back wall of the material. If a defect is present in a material then the sound energy will be reflected from it and received by the probe earlier than the signal from the backwall doe to the sound having not travelled as far. The strength or amplitude of the echo will give an indication of the defect size and the distance travelled by the sound will indicate its depth.
Using modern technology, ultrasonic thickness guages or flaw detectors can locate defects within welds and metals and provide qualitative and quantative information about the defect.

UT can be used in the following applications: -

Corrosion / Erosion monitoring of pipes and storage and pressure vessels
Measuring wall loss in steel columns and beams
Weld flaw detection
Lighting Column Inspection

Magnetic Particle Inspection (MPI) is an inspection technique used for the detection of surface or near surface flaws in ferromagnetic materials and is used primarily for crack detection in welds, forgings and castings. It is a recognised and proven technique that can be carried out both topside and sub-sea. MPI is also used in conjunction with Eddy Current Inspection to confirm defect signals once the coating has been removed and the surface is prepared.

Some of the benefits of Impact-Echo include: -
* Rapid testing
* Lightweight and portable system
* Not detrimental to structure (no focal points for future deterioration)
* Stand alone system
* Collected data can be stored for audit or review
* Imago Software operates in Windows environment allowing easy interface with other applications