Tank scanning & API 653: shell, settlement and deformation

What is tank scanning?

A tank is scanned from the outside (and, where needed, inside) using terrestrial laser scanners positioned around and above the structure. The scanner records millions of points across the shell, roof and surrounding foundation, which are registered into one coordinate system to reconstruct the tank's actual geometry — not the nominal design geometry, but the shape it has settled into after years or decades of service.

How it supports API 653 inspection

API 653 governs inspection, repair, alteration and reconstruction of aboveground storage tanks, and calls for evaluating shell distortions, settlement and out-of-roundness against defined tolerances. A survey-grade point cloud gives the inspection team an objective geometric baseline to check those criteria against — rather than relying on spot measurements at a handful of points around the shell.

The point cloud and derived reports are inputs to the inspector's fitness-for-service evaluation; the engineering judgement and API 653 sign-off remain with your qualified inspector.

What you get

• Registered, QA'd point cloud of the shell, roof and surrounding foundation
• Shell profile / verticality data at defined elevations and radial positions
• Out-of-roundness and settlement analysis, referenced to the tank's own datum
• As-built 2D/3D of the tank and associated piping, where required

Reading shell deformation and settlement

Once the point cloud is registered, we can extract vertical shell profiles at any radial position, compare the tank's actual roundness to a best-fit circle, and quantify how much the foundation has settled — differentially or uniformly — relative to the tank's original construction. These outputs feed directly into the tolerances your inspector is checking against under API 653.

Scanning without entry — access and safety

Exterior shell and roof scanning is typically done from ground level and from a perimeter walk, often supplemented by drone capture for roof and upper-shell areas that are hard to access safely. Interior scanning, where required, is planned around your entry and confined-space procedures. See Oil & Gas for how tank scanning fits into our broader as-built work for this sector, and our note on scanning for turnarounds.

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