. Development and evaluation of a motion compensating lift system for deep ocean construction. Underwater construction; Marine engineering; Civil engineering. range of ship periods H_j' a;(rad/sec) Period (sec) Figure 8. Response ratio for 6,000-foot wire at 5% rate, showing effect of mass/weight ratio. by a pneumatic spring cylinder. A pair of hydraulic cyUnders are used to control the boom position when operating in a "hard" (noncompensated) mode. With the hydraulic cylinders in operation, the system is capable of lifting loads in the same manner as with a conventional cran
. Development and evaluation of a motion compensating lift system for deep ocean construction. Underwater construction; Marine engineering; Civil engineering. range of ship periods H_j' a;(rad/sec) Period (sec) Figure 8. Response ratio for 6,000-foot wire at 5% rate, showing effect of mass/weight ratio. by a pneumatic spring cylinder. A pair of hydraulic cyUnders are used to control the boom position when operating in a "hard" (noncompensated) mode. With the hydraulic cylinders in operation, the system is capable of lifting loads in the same manner as with a conventional crane. During operation in the com- pensating mode the hydraulic cylinders are short- circuited and, thus, effectively removed from system operation. The pneumatic spring is the central component of the compensating system, and its characteristics determine how well the system operates. Figure 16 shows a simplified spring circuit. A pneumatic cylinder is used to directly support the boom, pay- load, and lift line. To obtain the required, relatively small, pressure changes over the boom stroke, additional gas volume is provided from eight separate high-pressure gas bottles that can be connected together in a variety of ways using the manual cross- connect valves (12C through H in Figure 16). Accumulator volume is also varied during operation as a function of boom position to increase the spring constant as the boom approaches the lower limits of its travel range. To accomplish this, a mechanical scotch yoke arrangement is activated by pins attached to the boom. Three separate yokes are used to control valves 12A and B and 23, allowing the accumulator volume to be reduced in three incremental steps. Valve 23 is the last of the three to be activated and completely separates the spring. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble t
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Keywords: ., bookcentury1900, booksubjectcivilengineering, booksubjectmarinee
