Averting disaster
Tank collapse can be both costly and dangerous, so regular tank inspection should be a priority for all terminal operators
Recent incidents in Belgium, Canada, India and other locations are vivid reminders of the importance of maintaining tank integrity. Periodic inspection of a tank, though arbitrary to a certain extent, is determined by a number of factors outlined in the Engineering Equipment and Materials Users Association (EEMUA) guide 159, Users’ guide to the inspection, maintenance and repair of above ground and vertical steel storage tanks, the American Petroleum Institute’s (API) 653, Tank Inspection, Repair, Alteration and Reconstruction, and API Recommended Practice 575, Inspection of Atmospheric and low pressure storage tanks.
The most vulnerable part of the tank is the bottom, which requires internal inspection. Experts suggest that tank bottom inspections should normally be carried out at intervals of six to 15 years. Where corrosion rates are unknown, inspection intervals can be shorter.
Tanks have to be taken out of service for internal inspection, with consequent downtime, cleaning and waste oil disposal costs. Consequently, nonintrusive systems for detecting cracks or corrosion can be very costeffective, using either acoustic emission (AE) or long range non-destructive testing (NDT). Neither approach requires internal entry but if a fault is revealed, tank entry may be required to determine the extent of the damage.
