to determine how serious the leakage would be at shallow depths . 



At the start of the salvage tool tests it was not known how often 

 the hydraulic fluid should be changed to prevent pump failures . It was 

 decided to begin with a weekly hydraulic fluid change and increase the 

 time between changes during the test program. Near the end of the tests 

 the fluid was not changed for over a month. Although there were always 

 small amounts (<3%) of water in the hydraulic fluid when it was drained 

 from the pumps , the corrosion inhibitors in the hydraulic fluid prevented 

 any pump corrosion. It is estimated that this type of hydraulic pump 

 with no maintenance or pressure compensation has a minimum life of 

 several months in shallow water when a corrosion-inhibited hydraulic 

 fluid is used. 



Hydraulic Cylinders 



The two types of hydraulic cylinders tested underwater are shown 

 in Figure 11. The top one is a double-acting cylinder which was used 

 for pulling. The bottom one is a single-acting cylinder (ram) for 

 pushing or jacking. Double-acting cylinders can be used in either a 

 push or pull mode, whereas single-acting cylinders can exert a force 

 only in one direction and are usually returned to their retracted 

 position by an internal spring. The advantage of using rams for lifting 

 and pushing is that the rod (piston) is much larger than a double-acting 

 cylinder rod with the same size housing. This is important because the 

 ram is loaded as a column and must resist lateral deflection. Both of 

 the ram and cylinder were used with the diver-powered hydraulic pumps . 



The ram shown in Figure 11 is capable of lifting loads to 10 tons. 

 With various extensions, end connections and accessories, it is typical 

 of the "hydraulic rescue and maintenance sets" used to move heavy equip- 

 ment in industrial firms. Some typical ram and accessory combinations 

 are shown in Figure 12. These accessories have a five ton rating. The 

 ram and accessories are connected together with either threaded couplings 

 or connectors that slide inside the pipe extensions and are locked in 

 place with pins (see Figure 13) . 



The two purposes in testing the hydraulic rams were to (1) determine 

 the diver's ability to select and assemble the correct accessories 

 underwater to fit an opening; and (2) to determine the forces that the 

 ram end connections would support without slipping on flat perpendicular 

 and sloping surfaces . 



The time required for the divers to select components from the tool 

 box shown in Figure 14 and to assemble them with the ram to fit a 60-inch 

 horizontal span is shown in Table II. 



12 



