New Terminal Storage Tank Standards On Horizon To Prevent Seismic Damage
Aug 1, 2001 12:00 PM
NEW STANDARDS for storage tank construction are being considered by the American Petroleum Institute (API) to meet seismic considerations. Although previous standards met some of the requirements should an earthquake occur, the need for resistance to tidal wave flooding and for tank flexibility are now on the board, according to information presented during the Independent Liquid Terminals Association (ILTA) meeting June 11-14 in Houston, Texas.
Philip Myers, tank, piping, and pressure vessel specialist with Chevron, noted that companies along the Gulf Coast and on the East Coast are more likely to be challenged by the new standards than those on the West Coast, which already have stringent regulations in place and have experienced earthquakes.
“There will be big changes in tank construction,” he said.
The API standards under consideration are being driven by new regulations established in the International Building Code (IBC), primarily for buildings, but including storage tanks. The 1997 National Earthquake Hazards Reduction Program is the basis for the IBC, according to a paper prepared by Ty Hagen, president of Hagen Engineering International Inc, St Paul, Minnesota, and presented by Laurie Marty of Hagen Engineering.
When an earthquake occurs, storage tanks are threatened with shaking, ground ruptures, landslides, and tidal wave flooding. The extent of damage depends on the structure's particular construction and the intensity of the earthquake, she said.
The new standards are expected to call for more complex calculations before new tanks are constructed. More local seismic data will have to be collected and weighed for its impact on the design. Companies may want to choose areas with firm soil support and away from fault lines, she added.
Some existing tanks may meet the new standards, but others fail to even satisfy those already in place, she pointed out. Companies with storage tanks that fail to meet the standards face not only the risk of damage to their property, but of increased liability, she said.
Myers noted that some adjustments may be relatively simple. Piping and ladders can be made flexible so that they do not rupture or pull away from the tank. Less product can be stored in the tank to prevent it from erupting through the top should the pressure inside increase from sudden vertical movement. Allowances will have to be made for storage tanks with floating roofs to prevent them from rocking and bumping into the walls of the structure.
“Common sense is going to settle a lot of these rules,” he said.
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