500 psi, a consequence of the industry's capacity to build smaller and more efficient equipment (Gilchrist, 1999). The advent of complex, sophisticated electronic technologies and "smart applications," coupled with rigorous standards for hydraulics operations promulgated by agencies such as OSHA, has driven these developments. The industry as a whole is said to be experiencing a shift toward systems design rather than component design (Gilchrist, 1999).
In submarine operations, hydraulics are of growing significance (Things haven't been..., 1998). Hydraulically operated vents have long been used to fill and empty tanks located between the out skin and the pressure hull, causing the submarine to rise or descent in the water. The Navy uses many devices that are operated on the hydraulic principle on surface and submarine craft. Pumping seawater and oil into and then out of ballast and other tanks requires a complex system of hydraulics that must be designed to meet the specific needs of the vessel. Hydraulic pumps, rams and lines are used for this purpose. Ballast tanks control the trim, or balance, fore and aft, of the submarine. The main ballast tanks have the primary function of either destroying or restoring positive buoyancy to the submarine. Allowing air to escape through hydraulically operated vents at the top of the tank lets seawater flow through the flood ports at the bottom to replace the air. For the sub to regain positive buoyancy the tanks are "blown" free of seawater with compressed air (Thinks haven't been..., 1998).
One of the benefits of using hydraulics is that the lines through which fluid flows and pressures exerted are flexible and can therefore be extended around corners; they can also be segmented to ensure that fluid and pressure move as desired, and they can be operated by remote control from the bridge or engine room of a ship (Things haven't been...,1998). Three points about the operation of these d...