James Fisher & Sons PUBLIC LIMITED COMPANY - the leading provider of marine services

Remote Access Corrosion Mapping and Thickness Measurements

Thickness measurements of tanks, pressure vessels, pipe work and other steel structures is an important part of periodic inspections and in some cases may be a statutory requirement. JFIMS have a range of remote access crawlers fitted with ultrasound thickness measurement probes which can climb ferro-magnetic structures for repeatable and reliable inspections. Thickness measurements can be used to monitor for corrosion, erosion and defects including hydrogen blistering. The crawlers are also effective at inspecting vessel linings.

JFIMS makes extensive use of remote access crawlers because they offer distinctive advantages for the delivery of cost-effective services.

  • The crawlers are rapid and reliable and can travel and operate vertically, horizontally and even upside down.
  • There is no requirement to use scaffolding to access the vessel surface.
  • It is possible to rapidly mobilise the crawler for inspections.
  • The rapid mobilisation and speed of inspection minimises the time on site and the disruption of operations.
  • With umbilical lengths of 30m, the crawlers can access the majority of structures.

For corrosion mapping, JFIMS use Silverwing RMS corrosion mapping systems. The RMS is a C-scan imaging system mounted on a magnetic crawler to enable reliable and safe remote access to ferro-magnetic structures. The RMS crawler has a scan width of 600mm for large areas and 300mm for more constricted surfaces and pipework. With a scan speed of up to 730mm/second, the RMS can rapidly map the thickness of a steel structure and automatically record the A-scan image, the C-scan image and the thickness measurement for analysis and reporting. In practice, with the 600mm scan width, 12m can be scanned in an hour.

For thickness measurements, JFIMS employ Silverwing Scorpion crawlers. The Scorpion is a lightweight magnetic crawler with a 5MHz twin crystal transducer which records spot thickness measurements. The Scorpion crawler is capable of climbing any ferro-magnetic surface and is particularly manouevreable and suitable for recording thicknesses around pipe junctions and nozzles.