Non-destructive testing robots (NDTBOTS) for in-service storage tank inspection

Petrochemical storage tanks are inspected mostly with outages to assess the extent of underside corrosion on the tank floor. Emptying, cleaning and opening a tank for inspection takes many months and is very expensive. Inspection costs can be reduced significantly by inserting robots through manholes on the tank roof and perform non-destructive testing. The challenge is to develop robots that can operate safely in explosive and hazardous environments and measure the thickness of floor plates using ultrasound sensors. This paper reports on the development of a small and inexpensive prototype robot (NDTBOT) which is easy to make intrinsically safe for zone zero operation. It hops around a floor to make measurements without using external moving parts. The paper describes the design, experimental testing of the NDTBOT and results of steel plate thickness measurement while operating in water.