Technical Information
How does remote laser inspection work?
CIAI uses the drill stem as our platform for performing the inspection service. The drill-cutting nozzle is removed to fit one of our drill stem extension adaptors. The instrument is then installed from either the top or bottom head access point where there is a minimum 30” diameter nozzle. The instrument is raised and lowered in the drum using the existing drill stem controlled by the site’s trained operator.
Once installed, CIAI technicians operate the instrument remotely from a climate controlled shelter located at ground level. Site inspectors can monitor the inspection activity from this same location. There is no need for technicians to work in the open air or under temporary cover at the top or bottom head of the drum. Local site restrictions, which limit human access to the structure during drum cutting of adjacent drums, are not a concern while performing the inspection. CIAI’s processing software accommodates the off-center and movement issues of a drill stem operating on an in-service coker unit.
A complete laser and video inspection (including installation and removal of equipment) can be performed in less than 4 hours. This ensures that the video information is gathered in the same time frame as the laser data. Azimuth and elevation readings are permanently recorded on the video and correlate directly to the laser mapping. The ability to cross-reference between the two inspection formats makes it easier to confirm that an anomaly found in the laser data was not just a build-up of coke, for example.
Customer drawings are used to create weld seam overlays for each drum. The weld seam overlays can be amended in the case of repair areas. Before starting each scan, the laser spot is pointed at a known and repeatable target (usually the intersection of a vertical weld with either the top or bottom tangent weld) within the vessel to establish a reference point. This is essential when performing comparisons on year-over-year drum scans. The ability to point the laser spot and set a reference to register the weld seam map with scanned profile data ensures the proper overlay of year-over-year drum profile data. CIAI’s laser scans do not rely on identifying subtle distortions in the drum surface to indicate weld seams. This approach is inaccurate at best and can break down when welds are either flush ground or coke covered.
Like any laser-based system, data can be missed on very reflective surfaces caused by water and/or oil on the vessel wall. CIAI’s laser range camera system can be tuned on-line to accommodate almost all vessel wall surface conditions..
