Crawler and Corrosion Mapping
Scanning a tank floor or a large shell by hand is slow, and it often means long periods inside a confined space. A crawler carries the probes across the surface while the operator stays outside.
About crawler inspection and corrosion mapping
Corrosion mapping across a tank floor or a large shell involves taking a great many readings over a large area. Done manually it is slow and physically demanding, and on internal surfaces it keeps an inspector inside the tank for extended periods, with all the controls that confined space working requires.
A crawler carries the inspection to the surface instead. Tracked crawlers and magnetic wheeled crawlers hold ultrasonic or magnetic flux leakage probes against tank floors, shells and other large steel surfaces, driven and monitored by an operator positioned outside the space.
Because the crawler is encoded, every reading is tied to a position on the surface. That produces a corrosion map showing where metal loss is occurring and how deep it goes, a far more useful picture than isolated spot readings, and one that can be repeated and compared at the next inspection.
Inspection scope
A crawler survey is set up around the surface, the access and the degradation being assessed. Scope commonly includes:
- Ultrasonic thickness mapping of tank floors and shells
- Magnetic flux leakage floor scanning for top and underside loss
- Corrosion mapping of large plate and vessel surfaces
- Encoded scanning that ties every reading to a position
- Identification and sizing of pitting and general metal loss
- Comparison against previous surveys to establish corrosion rates
- Data and mapping to support fitness-for-service assessment
Why use crawlers for corrosion mapping
Keeps operators outside
The crawler carries the probes across the surface, reducing the time an inspector spends inside a confined space.
Covers large areas
Scanning is faster and more consistent than manual readings across a floor or a shell of any size.
Position-accurate data
Encoded scanning maps metal loss to the surface, so findings can be located, sized and tracked.
Supports fitness-for-service
Corrosion mapping feeds directly into remaining life and fitness-for-service assessment of the asset.
Reporting and recommendations
Every crawler survey produces a clear report and a corrosion map setting out where metal loss is occurring, how severe it is and how it compares with previous inspections, with the encoded data behind it.
Where the mapping shows significant loss, we set out what it means for the asset and recommend the appropriate action, from continued monitoring to repair, and provide the data needed for remaining life and fitness-for-service assessment. Reports are written by the inspector who carried out the survey.
Related inspection services
Need to map corrosion on a floor or shell?
Speak with our team about crawler surveys and corrosion mapping for your tanks and large surfaces.