Thickness Inspection

Thickness Inspection

The requirement for accurate thickness measurements is found across many industries including aerospace, oil and gas, pharmaceutical and food processing.  Either for quality control in manufacturing or in-service verification often access is only available from one side and speed is critical.  The wall thickness from most materials can be measured ultrasonically including metals, composites, plastics and glass using a simple hand-held digital gauge.

In certain environments, a coating of paint or other non-metallic material may have been applied to protect the part.  A common application would be a painted pipe used in the petrochemical industry.  In this case a conventional ultrasonic gauge would give measurement errors from the presence of the paint.  However, with the correct gauge with through paint mode, measurement through the paint is possible resulting in the correct wall thickness measurement underneath.

NDT Systems offers a range of standard and high-resolution thickness gauges with features including A-trace display, B-scan, automatic probe recognition, data logging and much more. Furthermore, large area thickness mapping (C-scan) can be achieved using our Raptor imaging flaw detector and range of scanners.

Transducer (Probe) Type

Contact transducer – probes which transmit a pulse of compressional sound into the specimen at the right angles (normal) to its surface. It is the most common used transducer type for thickness measurement.

Delay Line transducer – in order to facilitate the complete inspection of thin plate sections it is necessary to eliminate the effect of the probe units dead zone and the earlier part of its near filed in which those areas of the interfering sound pressures exist. A normal angle probe is mounted on a plastic, epoxy or fused silica known as a delay block between probe element and test specimen

Immersion transducer – special waterproofed probes used in immersion testing which allow thinner and higher frequency crystals without face wear plates can be used with less chance of damage caused by probe handling encountered during contact scanning

Dual Element (Twin Crystal) transducer – comprises two crystals act as transmitter and receiver respectively which gives good sensitivity to near surface defects and measurement.


  • Metals
  • Plastics
  • Composites
  • Glass
  • Fiberglass
  • Ceramics

Typical Applications

  • Turbine blade thickness
  • Corrosion & pitting
  • Boilers Glass
  • Storage tanks
  • Pipes and tubing
  • Metal sheet processing
  • Aerospace & automotive manufacture
  • Investment Castings
  • Chemical milling


As the use of adhesively bonded joints and fittings has increased across many industries,  the need for testing bond integrity has grown. Metal to metal bonded joints, sandwich constructions with various skin and core materials, bonded carbon fibre composite structures have all become important in manufacturing as well as in-service repair patches and adhesively bonded re-inforcements. The integrity of these bonds is critical to the quality of the final product. Conventional ultrasonic methods can be limited for these applications and so a variety of alternative methods have been developed to handle this range of material combination.

Inspection Methods:

  • Pitch-Catch RF
  • Pitch-Catch Pulsed
  • Pitch-Catch Swept
  • MIA Fixed Frequency
  • MIA Swept Frequency
  • Resonance


Non-Destructive Testing by Shearography

Non-Destructive Testing by Shearography

Shearography is an optical Non-destructive testing method that provides fast and accurate information about internal anomalies in different materials. Sherography is being extensively used in production, research and development and in-field within the aerospace, automotive, marine and wind industry.


The main applications for shearography are for quality assurance of composite and other materials. Depending on the material strength and depth of defects within a sample, Shearography can detect most discontinuities that occur in composite structures, including disbonds; delaminations; cracked core; crushed core; kissing bonds; wrinkling; fluid ingresses; porosity; cracks; repair defects; and impact damage (BVIDs). Additional structural information such as ply drops, bulkheads, overlaps, splices, stringers, ribs can also be detected.

Loading Conditions:

  • Thermal
  • Vacuum
  • Vibration
  • Acoustic
  • Mechanical

Inspection Standard:

The NDT industry is controlled by Inspection Standard Documents. Shearography is incorporated in the following standard documents:

  • ASNT CP-105
  • ASTM E2581