Greater attention for inspection of storage tanks

Serious and costly accidents involving conventional storage tanks have triggered a greater awareness in terms of safety, nondestructive testing (NDT), cost and environmental issues, reports inspection technologies company Rosen Group.

NDT company Ultraspec-NDT has been working with Rosen Group on various oil and gas, and petrochemical plant integrity assessment projects, using advanced technologies such as intelligent pigging for pipelines, and more recently storage tank inspections using magnetic flux leakage and other NDT methods.

Rosen Group states that governments throughout the world have, during the 90s, progressively strengthened the legislative requirements concerning the integrity and inspection frequencies of storage tanks.

Prior to the 90s, tanks were seen as the ‘ugly duckling’ within the refinery or chemical plant and, as a result, minimal budget and effort was expended for tank maintenance. Further, in some incidents, fire fighting and repair work had to be undertaken owing to poor maintenance guidelines.

While tank-accident precautionary-measures contribute significantly to safe operation and environment protection, it does present problems, as well as increase operational and capital cost for the tank owners. The biggest problem is determining a tank’s condition after it has been in service for several years.

Moreover, Rosen Group suggests that asset owners are currently reducing maintenance budgets in general, to fulfill their financial obligations with respect to share- holders. This often creates conflict with the existing maintenance plans and goals introduced in the 90s.

Often, risk-based inspection methodologies are recognised as the solution to the problem.

Thorough inspection of storage tanks, based on priorities stipulated by inspection records, visual observation or on-stream monitoring, is viable with techniques such as acoustic emissions, used to create a first impression on tank- bottom corrosion activities or leaks in the bottom plates with consequent decommissioning of the tank.