ASTs are fabricated using steel ground plates welded to an annular base ring, and to each other. These tank farms are normally found in areas close to large population centres and near coastal industrial zones where the corrosive environment is harsh due to saline spray, humidity, the aggressive chemicals stored and high temperatures. The majority of tanks in Europe are over 30 years old and the corrosive environments in which these operate makes the danger of leakage acute. In a worldwide survey on tank ruptures carried out in 1988, API found that these incidents accounted for almost 19% of released material into the environment. In Japan for example more than 50 leakage accidents in ASTs were reported in 2003 and about 60% of them were due to corrosion. Hence there exists the potential of damage to the environment, plus endangerment of civilians and working personnel, as well as the interruption of the operator's business.
Globally there are over 500,000 storage tanks of which almost one third are in Europe (166,000, of which 40,000 are large petrochemical tanks). The market size is calculated to be worth €800m in Europe and €2.8bn worldwide.
The SafeAST system provides continuous structural condition monitoring of ASTs, detecting any corrosion hotspots in the internal tank floor without the need to empty the tank and manually inspect the welds. It is a system that provides continuous monitoring by integrating its long range ultrasonic testing (LRUT) with sophisticated sensors and systems in order to detect defects in the annular ring and bottom plates.
Based on the 2007 API Standard 653, the current industry SOPs are to periodically evacuate the AST contents to another vessel, open all the tank hatches, de-gas or neutralise chemicals and clean them. Trained non-destructive testing (NDT) personnel then enter the vessel to evaluate tank integrity, inspecting and repairing the tank floor if necessary. This is a dangerous occupation and accidents to NDT operators resulting in injury or worse are not uncommon as explosions sometimes occur. The emptying and cleaning operation releases huge amounts of hazardous vapour into the atmosphere but the proposed SafeAST solution will largely eliminate this pollution.
The proposed SafeAST solution will largely reduce the pollution, disruption to the service and cost by reducing the need to open the tank less frequently since the condition of the tank floor can be monitored by a number of attached sensors located around the external perimeter of the AST.