INTRODUCTION 



Background 



Handling heavy loads in the ocean is usually 

 restricted by ship-motion-induced dynamic line loads 

 that can be many times the magnitude of the static 

 load. The manner in which the restrictions limit the 

 load-handling operations is governed by the weather, 

 ship, payload, and line characteristics. Many attempts 

 have been made in recent years to develop a system 

 that would compensate for ship motion and thus 

 reduce the dynamic forces in the cables. Such com- 

 pensation would provide a higher reliability and a 

 greater safety factor in load-handling operations. 

 Notable among these attempts are the passive ram- 

 tensioner system designed for the Navy's Large 

 Object Salvage System* [1] and the numerous active- 

 type "constant-tension" oceanographic winches. 



Performance Objectives 



With the Navy's increasing interest in placing 

 heavy loads on the ocean floor a system is needed 

 that is capable of lowering or raising multiton loads in 

 the ocean with a minimum of restrictions imposed by 

 weather-caused ship motions. This requirement is 

 included in the Deep Ocean Technology Technical 

 Development Plan (DOT TDP)**. The performance 

 characteristics defined by the DOT TDP 

 are: (1) depth capability of 6,000 feet; (2) load 

 capacity between 20 and 100 tons; (3) lowering or 

 lifting rate of 1 to 2 ft/sec ; (4) maximum dynamic 

 stress in the lift cable of 10 to 30% of static stress; 

 (5) maximum vertical oscillation of the load of 1 to 3 

 feet with respect to the bottom, and (6) an opera- 

 tional capability in sea state 3. 



The Naval Facilities Engineering Command 

 (NAVFAC) assigned the development of the desired 

 lifting system to the Civil Engineering Laboratory 

 (CEL). A complete set of performance specifications 

 (listed in Table 1) was developed based on the DOT 

 TDP, the current state-of-the-art, and predictions of 

 how far the technology could reasonably be advanced 

 in one step. The ship motion limits were obtained 

 from operating records obtained during previous CEL 

 work aboard ATF and ARS vessels. In addition to the 

 requirements of Table 1, it was specified that the 

 system be self-contained, physically compact, suitable 

 for use aboard vessels such as the ATF, ARS, ASR, 

 and capable of utilizing wire and synthetic lift lines. 



CONCEPT SELECTION 



Alternative Concepts 



Five different concepts were evaluated and 

 judged on their potential ability to meet the perfor- 

 mance objectives (Table 1). Of these, four were of the 

 active, feedback, servo-controlled type, and one was a 

 passive, nonfeedback system. Two of the active 

 systems used the line-storage drum as the main 

 traction and compensating unit, and two utilized a 

 driven traveling block to provide some of the required 

 compensation capability. 



Of the single-drum concepts one was to use a 

 diesel-hydraulic system to drive a hydraulic drive 

 motor. The other was to be driven directly by a diesel 

 power source connected through a constantly slipping 

 servo-controlled clutch. 



One of the traveling-block concepts included a 

 hydraulically driven traction/line-storage unit 

 combined with a servo-controlled hydraulically driven 



* Hydronautics, Inc. TR-613-1; Large object salvage system (LOSS) feasibility and analytical 

 studies, by E. R. Miller, Jr. Laurel, MD, Dec 1966. 



** Classified reference. (Reference citation available from Civil Engineering Laboratory, Naval 

 Construction Battalion Center, Port Hueneme, California 93043, to qualified requestors 

 with need to know,) 



