OCEAN-BOTTOM MINING TECHNOLOGY 



403 



1/4" t, 29-3/40 Di 

 24" I. D. 



2"0.D. X 1-3/4" ID. 

 3-3/4" LG. 



LIFTING RING 

 2-l/2"O.D. 1-3/8 

 3 PLACES 



I X I X 1/8 LS 5-3/4 LG. 

 6- EQUALLY SPACED 

 WELDED 



Fig. 165. Conical shoe used on the bottonn of the 

 air lift recovery pipe 



Sealab II Tests 



An airlift with a two- inch recovery pipe was lowered from USNS Gear in 185 ft of water 

 near the Sealab II site. Compressed air was supplied from Gear at 140 psi and 50 cfm. Ini- 

 tial two-phase (air/water) flow was established at 10 gallons per minute, one minute after com- 

 pressed air was supplied to the manifold. Very few solids were observed in the water flowing 

 into the recovery barrels, and pumping was discontinued after 15 minutes. Examination of the 

 recovery barrels disclosed only a few ounces of very fine sediment, principally mica flakes 

 averaging 2 mm in diameter, and light silica particles. 



Observing divers reported that sediments at the location were highly compacted and cap- 

 able of supporting considerable weight. Based on this information, it was decided to increase 

 the seawater intake velocity by decreasing the effective area of the shoe. The original shoe 

 was modified aboard Gear to Bureau engineer's specifications. 



The diving team was then instructed to distribute several pounds of phosphorescent sand 

 over a ten- foot- diameter circle around the recovery shoe and observe the lateral movement of 

 the sand into the system with an ultraviolet light. The divers reported no perceptible move- 

 ment of the sand; however, phosphorescent sand was observed in the recovery barrel. Airlift- 

 ing operations were terminated after 10 minutes. 



