Why Can't We Get the Lead Out?
1996; Wiley; Volume: 108; Issue: 3 Linguagem: Inglês
10.1111/j.1559-3584.1996.tb01556.x
ISSN1559-3584
Autores Tópico(s)Technology Assessment and Management
ResumoABSTRACT U.S. Navy surface ships are designed with service life allowances to accommodate growth throughout their careers without exceeding original weight and stability limits. Adopted in 1986, the current criteria provides from five to ten percent of full load departure weight margin and 0.5 to 2.5 feet of full load departure KG margin based on ship type. The previous criteria proved inadequate: only twenty percent of the surface fleet is classified in Stability Status I (no displacement or stability problems). Ships inevitably get heavier, and become less stable, as new equipment and systems are added above the center of gravity. This trend is exacerbated by undocumented weight growth, which further eats into the service life allowances. Rather than remove topside weight or add blisters in service, lead ballast is regularly used as the “cheap fix” to maintain or restore adequate stability at the cost of added weight. As a result, the surface fleet is currently carrying a total of 27,711 tons of lead (and pig iron) ballast. But, with average installation costs exceeding $5000 per ton, lead ballast is not an inexpensive solution. If growth is necessary for the continued modernization of the surface fleet, inadequate service life allowance can lead to premature obsolescence of otherwise good hulls. This is particularly true for surface combatants. The current criteria was first applied in the design of the notably stockier DDG‐51 Arleign Burke Class destroyers, which have been provided with a ten percent of full load departure weight margin and a 1.0 foot of full load departure KG margin. Only time will tell if this service life allowance criteria is adequate, but early growth and previous trends for surface combatants are cause for some concern.
Referência(s)