A 45-metre cooling tower audited without scaffolding, in five elapsed days.

The operator hyperbolic concrete cooling tower was approaching a planned major outage. Before shutting down, the engineering team needed an objective structural audit to define the repair scope, quantify materials, and justify the outage budget. The conventional route was scaffolding plus a multi-day manual inspection, at an estimated cost of several hundred thousand rand and a lead time of weeks.

The constraints were tight. The tower was still in operation during the audit window. The audit was required to hold up for procurement of repair contractors (meaning material quantification had to be tender-grade), and for the operator insurance renewal process (meaning Pr Eng sign-off was mandatory). The client wanted a single accountable partner from capture through audit to material take-off.

Delta Scan proposed a three-phase condition audit combining aerial capture of the external envelope and Omnispect-based 360-degree internal inspection, followed by full engineering interpretation.

Phase one was scoping. We reviewed the original construction drawings, prior inspection records, and the operator intended outage scope. The defect taxonomy agreed covered concrete spalling, rebar exposure, cracking (classified by width and orientation), surface deterioration, and internal deposit build-up. Repair methodology templates were aligned to SANS 10100.

Phase two was capture. A single operational day of capture used the DJI M350 RTK with the H20T payload for the external surface and the 360-degree rig for internal inspection through an access port. Thermal imagery captured during the same flight supported delamination detection. The operator required no shutdown during capture.

Phase three was processing and reporting. Imagery and 3D data were processed into a spatially referenced model of the tower, with defects overlaid and dimensioned. Omnispect annotation workflow classified internal defects with bounding polygons, leader lines, and zoom insets for review. Our engineering team reviewed each classification, quantified repair materials for each defect class, and produced a tender-grade audit report. The final deliverable was signed by a Pr Eng.

• UAV platform. DJI M350 RTK
• Payload. DJI H20T (thermal and 4K)
• 360 video. 5.7K 360-degree camera rig
• Processing software. Omnispect, photogrammetric reconstruction pipeline
• Delivery environment. DeltaCloud with annotated 3D model
• Standards. SANS 10100, SANS 10160

• Day 0. Scope, record review, taxonomy sign-off
• Day 1. Single-day on-site capture (external UAV + internal 360)
• Day 2 to 4. Photogrammetric reconstruction, Omnispect annotation, engineering review
• Day 5. Tender-grade audit report and material quantification delivered

The operator issued repair tenders against the Delta Scan audit material quantification, compressing what had historically been a three-month repair scoping cycle into under three weeks. The planned outage window was reduced because the repair scope was fully defined in advance.

The Pr Eng sign-off was accepted by the insurer for the next renewal cycle. Delta Scan has since been commissioned for condition audits on two further assets in the same portfolio.