where f = friction factor 
h, = pressure drop (ft) 
L = hose length (ft) 
D = hose inside diameter (ft) 
V = fluid velocity (ft/sec) 
gravity (ft/sec) 
ico) 
Il 
The results are presented in Figures 8, 9, and 10. The major inefficiency of 
this system was presumed to arise from friction losses in the line. It should 
be noted in these figures that a decreased flow rate results in a substantial 
increase in efficiency, but requires a higher pressure at the motor and there- 
fore a stronger hose. The available commercial hydraulic hose limits application 
of the oil hydraulic system because when usable efficiencies are reached, the 
hoses cannot withstand the collapse pressures developed by the density differ- 
ence between oil and seawater. Hoses of 2-inch inside diameter with a working 
pressure of 5,000 psi and of 4-1/4-inch inside diameter with a working pressure 
of 3,000 psi are available but both hoses have a collapse pressure of 400 psi 
(Knechtel, 1967). Thus, considering only static head pressure, a vertical oil- 
filled line would collapse at about 9,000 feet below the surface. 
The seawater hydraulic concept was investigated as a closed system 
(Figure 11) and an open system (Figure 12) with flows of 29 gom, 57 gpm, 
and 86 gpm, as required for motor pressure drops of 6,000 psi, 3,000 psi, 
and 2,000 psi respectively in order to obtain the required 100 hp at the ocean 
floor. For this analysis, the same Moody curves and friction factor equation 
were used as for the oil system calculations. The results of the seawater hydrau- 
lic investigations are presented in Figures 13 through 18. Note should be made 
that good efficiencies can be obtained by reducing the fluid velocity of the 
system; however, as seen in the plots of hydraulic gradient, a decrease in the 
fluid velocity requires an increased system pressure and a stronger hose. 
Comparing the three hydraulic systems listed, the open seawater 
hydraulic system is the most efficient and compact. By using a hose of 2- 
inch inside diameter with an operating pressure of 5,000 psi (Knechtel, 1967), 
the filtered seawater open system (57 gom and 2-inch inside diameter) can be 
operated with 85% efficiency. The use of seawater also eliminates the hose 
collapse problem. 
