Framework of the Design of a Magnetic Crawler Device for Measurement of Coating dry film thickness on large storage Tanks

Abstract

The inspection of large crude oil storage tanks is critical for ensuring coating integrity, corrosion protection, and safe operation, yet conventional manual inspection methods are hazardous, time-consuming, and costly, particularly for large above-ground tanks. This study presents the design, development, and validation of a magnetic crawler device for automated measurement of coating dry film thickness (DFT) on large steel storage tanks. The proposed system integrates a lightweight mechanical chassis, permanent magnetic adhesion, differential-drive locomotion, an embedded DFT measurement probe, and a closed-loop software control architecture into a compact, field-deployable robotic platform. The hardware design enables stable adhesion and smooth traversal of vertical and curved tank surfaces, while the software system coordinates motion control, sensor feedback, data acquisition, and real-time wireless communication. Experimental evaluation was conducted under laboratory and field-representative conditions on coated steel surfaces, with manual DFT measurements used as reference values. Results demonstrate stable magnetic adhesion, reliable locomotion over weld seams, accurate and repeatable DFT measurements, and robust data logging and transmission. The average deviation between robotic and manual DFT measurements was approximately 1.1%, confirming measurement accuracy within acceptable industrial tolerances. The developed magnetic crawler significantly improves inspection safety, efficiency, and data consistency by eliminating the need for scaffolding or working at height. The proposed system provides a practical and scalable solution for automated coating inspection and asset integrity management of large storage tanks, with particular relevance to expanding oil and gas infrastructure in Nigeria and similar industrial environments.