Advanced Inspection

Time-of-flight diffraction (TOFD), a method of advanced ultrasonic testing, is a sensitive and accurate method for the non-destructive testing of welds for defects. 

The main benefit of using TOFD over Phased Array and conventional Ultrasonic testing, is that it relies on the detection of the diffracted wave mode rather than reflected energy. It detects the extremities of defects regardless of orientation making it ideal for detecting and sizing defects such as cracks, where the orientation of the defect may not cause a sufficient reflected energy and go undetected by the technician. 

ToFD is also an excellent tool for the detection and measurement of root erosion/corrosion surveys and is a complementary technique used alongside Phased Array for weld volume inspection.

See more about TOFD and our services using this advanced method of testing.

Phased Array ultrasonics has many different applications such as weld inspection, corrosion mapping, bolt and nozzle inspection. Glacier Energy specialises in the use of Phased Array for the construction of new piping, pipelines, vessels and structural welded members. This technique can also be used in petrochemical plants, when quick and accurate inspections are necessary due to time constraints during outages.

Used for the inspection of welds, Phased Array techniques can be used to inspect the full volume of the weld from one fixed position. The probe or elements can be steered electronically through a range of angles unlike conventional MUT where raster scanning is used and multiple angle probes are required.

Another advantage is that coverage can be confirmed using modelling software; this simulate the beams and ensure areas of concern are adequately covered with the correct angles for different areas of the weld such as fusion faces, weld volume/body, cap and root, ensuring maximum probability of detection.

Multiple scanning views can be viewed and utilised for more accurate analysis & reporting, and images can be transferred into final inspection reports.

Magnetic flux leakage is a magnetic method of non-destructive testing used for detecting and assessing areas that may be damaged by corrosion or pitting. This technique is mostly used on steel structures, such as pipelines and storage tanks.

MFL is essentially a flaw detection inspection system which will detect and quantify volumetric loss unlike an inspection system which will quantify minimum remaining wall/plate thickness. Generally, it uses hall-effect transducers to detect flux changes at the scanning surface caused by the influence of metal loss on the magnetic field.

Ultrasonic inspection of areas highlighted during the MFL inspection is an essential part of the inspection process to obtain minimum remaining wall/plate thickness.

Alternating current field measurement (ACFM) is an electromagnetic technique used for the detection and sizing of surface breaking cracks in metallic components and welds. It combines the advantages of the alternating current potential drop (ACPD) technique and eddy current testing (ECT) in that it can measure the size of the defect without calibration and the need for electrical contact.

Eddy current testing is one of many electromagnetic testing methods used in non-destructive testing (NDT) for flaw detection, as well as thickness and conductivity measurements. Eddy current testing uses electromagnetic induction to detect defects in both ferrous and non-ferrous materials by inducing an eddy current field in the specimen under test.
 
Eddy current testing equipment is highly portable, reliable and can detect very small cracks. Results are instant, ideal for on-site testing and plant inspections. One of the main advantages of this technique is that paint and thin coatings (<2mm t) doesn’t need not be removed prior to inspection.
 
Our inspectors are highly experienced in performing this non-destructive technique and are PCN or ASNT Levels 2 and 3 or ISO 9712 Levels 2 and 3 qualified in eddy current testing.

Surface: Eddy current testing is used to detect surface and near surface defects on relatively small areas; without the need to remove surface paint prior to testing. The equipment is light and compact and provides immediate feedback, making it ideally suited for inspecting on site.

Welds: As eddy current is best used for detecting surface-breaking cracks, this technique is ideal for the in-service inspection of welded structures that are subject to a cyclical loading that can lead to fatigue crack propagation in critical welded areas.

Tubes: Eddy current testing of tubes is an effective way of assessing the condition and lifespan of tubes and is used to detect corrosion, pitting, cracks, erosion and other changes to both the tube’s interior and exterior surfaces.

This technique detects corrosion, pitting and wall loss and is most commonly used for tube inspection in boilers, heat exchangers, air coolers and feed water heaters. It is particularly versatile as it is suitable for both ferrous and non-ferrous materials, and IRIS can be used on a wide range of tube diameters and wall thicknesses.

IRIS uses an immersion pulse echo technique whereby the ultrasonic transducer is centred in

the tube to be inspected. Ultrasonic pulses are emitted along a path parallel to the tube axis.

These pulses are then reflected by a 45º mirror into the steel.

As the mirror rotates, the ultrasonic beam is traversed around the tube circumference. All the measurements made during a complete scan around the circumference of the tube are displayed on a screen.

The complete display by way of a “B scan” image is regenerated for each revolution of the mirror, being triggered by the ultrasonic beam hitting the "target" built into the inspection head assembly. By withdrawing the inspection head from the tube at a pre-determined rate, the ultrasonic beam is made to describe a helical path with the individual revolutions producing a continuous series of measurements covering the full surface area of the tube.

Reflections from both the internal and external wall are detected using the IRIS technique, the time interval between the two being proportional to the thickness. Depending on the IRIS model being used, the minimum resolvable wall thickness for steel is in the range 0.5 to 1.0mm.

As with conventional ultrasonic testing, good coupling is required to remove any air interface between the transducer and the material under test. With IRIS, coupling is provided by the water flooding the tube. In some instances, there may be a tendency to lose the "flood" which results in complete loss of signal.

Corrosion mapping involves scanning one or more straight beam probes over a prescribed dual axis scan pattern over a pipe or pressure vessel surface whilst taking thickness measurements. The measurements are converted into digital values which are color-coded to create topographic C-scans of the vessel or pipe wall thickness profile.

To perform corrosion mapping, an automatic or semi-automatic scanner is used to scan an inspection surface using various ultrasonic techniques including pulse echo, pulse echo using PAUT and eddy current array.

Pulsed Eddy Current (PEC) is an advanced electromagnetic inspection technique used for detecting corrosion under insulation (CUI) on structures such as pipes, vessels and tanks. It is a quick and cost-effective solution for corrosion protection as it can be done without contacting the surface of the material as it doesn’t require surface preparation or the removal of insulation.

Using PEC, inspections can be conducted and corrosion can be monitored during operation to allow for planned maintenance and repairs to be scheduled and carried out at times optimal for your business.

Benefits include:

• No interference with production as PEC technology can be applied in-service
• No need to remove the passive fire protection. PEC technology can measure through up to 250 mm of material including the reinforcement mesh
• As it is a no-contact/non-intrusive method there is a high range of temperatures it can work through
• Performed in service during plant operation
• Accessibility issues are minimised as it can be used by rope access operators