Published on 13-Mar-2023

Phased Array Inspections at high Temperature

Phased Array Inspections at high Temperature


The present economic climate is focusing downstream Oil Companies to maximise the use of their production assets. 

The major push forward has been the reduction in maintenance period with the emphasis on increasing activities which can be carried out when the plant is on stream. Inspection on stream has many advantages for the operator, the more obvious being that there is no requirement to shut their plant down. Other gains to be made are that there can be a better planning for any subsequent remedial action before a planned shutdown.

This article will discuss the progress made by SonoInspec into the application of high temperature phased array leading to the present capability of continuous inspection capability at 350°C (662F)


To assist plant operators in maximising the availability of their assets and to reduce their shutdown time, SonoInspec has developed an online inspection strategy at plant operating temperature.

For in-service inspections when the plant is in full operation, SonoInspec has developed a set of “standard” procedures to be able to do corrosion mapping and weld inspections in low-alloyed carbon steel up to 662 F (350°C) with ultrasound technology. The result is that we can deploy the techniques HT TOFD, HT PAUT and HT UT wall thickness measurements, fast, reliable and at reasonable costs. 

For inspections from 662 F (350°C) up to 887 F (475°C) or for special configurations or special materials, we develop and validate specific procedures. 

Unique PAUT high-temperature inspection capability:

Special high temperature resistant PAUT probes and wedges were designed for SonoInspec, to be used up to 350°C (662F) full continuously. 

The wedges are designed with cooling channels to keep the temperature under control. Special couplant and wedge material is used to accommodate the ultrasound beam travelling into the material.  High temperature PAUT probes are made in a way that they can resist elevated temperatures.

The high temperature PAUT NII inspection method is the ideal solution for weld flaw detection, corrosion mapping and the detection of other types of cracking.

Case study

SonoInspec recently validated an inspection with high temperature Phased Array for one of their clients, witnessed by an authorised inspector.

  • Piping: 16”
  • Wall thickness 9.5mm
  • Temperature: 175°C (347 F)
  • Damage: Stress corrosion cracking in the weld and heat affected zone
  • Testing on a Sonaspection test plate with a root crack and a lack of fusion defect
  • Testing on a real samples coming from the plant of our client


With high temperature PAUT all defects could be detected at 175°C (347F). All defects could be sized as the tips of the defects were clearly visible. Only sizing of the lack of fusion crack was difficult, since the indication was not entirely “clean”. Further investigation of this indication is needed to be conclusive. Tips of the SCC cracking in the real sample were clearly visible and height sizing was possible with a good level of consistency. Results were verified with TOFD at ambient and at high temperature with HT TOFD.

If you want to know more about HT PAUT please contact us at or have a look at our website are call us/WhatsApp us at: +31624617755

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Application Notes