Inspection of storage tanks
20 August 2009
SGS Colombia S.A. was awarded the contract to perform storage tank inspections for the expansion works of the Cartagena Refinery. All inspection services were performed in accordance with Health, Safety and Environment (HSE) requirements.
Inspection of storage tanks
The storage of dangerous goods in tanks involves risk to the population, the environment, and the surrounding area, and must therefore be executed safely. Periodic inspection of the tank's condition, and in particular the tank’s bottom and shells, is of the utmost importance, in order to prevent disasters from happening and to reduce economic and environmental risks.
The expansion of the Cartagena Refinery is a strategic project for Colombia. The project aims to expand the refinery's capacity to 140 thousand barrels a day, as well as improve the quality of the fuels to meet national and international environmental standards, and to optimise financial and operational indicators. It is estimated that the project will be completed by 2010.
SGS Colombia was responsible for the inspection of floating-roof and conical-roof tanks with sizes between 20,000 to 130,000 barrels. In terms of the Non-Destructive Testing Services for storage tanks, the inspection carried out by SGS Colombia included the evaluation of tank bottoms and roofs, as well as tank shells.
For the inspection of tank bottoms and roofs, SGS inspectors used Ultrasonic Testing (UT) methods such as B Scan and C Scan in order to detect corrosion. B Scan provides a cross-sectional image of the material and detects material thinning which is caused by corrosion in the inside of tank walls. The C Scan is used as one of the last tools during the inspection process as it is more accurate than the B Scan. The C Scan is able to make cross-sectional images and identify failures of items located underground.
Conventional ultrasonic testing equipment works on the principle of sending a pulsed beam of high-ultrasound from a handheld transducer, which is placed upon the surface of the tank being tested. Sound energy in the form of waves is produced and propagated through the material, and then partially returned from areas with internal imperfections such as corrosion or from the back of the material wall. By analysing the returning sound, useful information about the condition of the tank walls can be collected.
For the assessment of the wall thickness of tank shells, SGS used an ultrasonic crawler, a tool designed to cost-effectively take ultrasound thickness measurements on above-ground ferro-magnetic structures, without the need for costly scaffolding or industrial rope access.
The inspection services required 12 qualified SGS inspectors in order to ensure precise performance of the inspection as well as correct identification and orientation of the imperfections and reporting of the findings. The SGS inspection services were carried out in accordance with applicable Health, Safety and Environment (HSE) requirements as well as to the API 653 Program.
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