OCR

The addition of milk of lime at the cyclone overflow is now controlled by a pH instrument actuating a pneumatic valve that keeps the pH at a con¬stant 10.4 to 10.5 for rougher flotation feed, and at 11.2 for cleaner flotation All high voltage electrical controls for the grinding section of the mill are now housed in a special refrigerated and pressurized room. The pressure is maintained at only a few ounces per square inch, but it is proving very effective in keeping dust out of the room and away from the sensitive switch gear. During the first month of expanded one ration, the concentrator operated a total of 97.57 percent of scheduled time. With the new electric shovels in the pit and additional equipment in the mill, electric power distribution facilities were greatly revised. Originally, one 7,500 kva. substation was sufficient for all Pima operations. However, with the new expansion this 7,500 kva. substation was moved to the pit area to supply power only to the skip hoist and auxiliary associated equipment. A. new 2,500 kva. transformer was then purchased to furnish power for the crushing plant facilities and the two electric shovels, and a new 10,000 kva. substation was purchased to supply power to the mill. The three new Pima substations receive an incoming voltage of 46 kv. which, in turn, is transformed down to 4. I kv. for local distribution. Elsewhere on the Pima property, the garage was exten-80 ft. to the west to provide four more truck repair bays--making a total of 10. Reagents used (pounds per ton) Lime............................................. 3.137 Z-6 (Dow Chemical Co.).......................... 0.0l4 Z-200 (Dow Chemical Co.)........................ 0. 035 R-104 (American Cyanamid Co.)................... 0.018 MIBC............................................ 0.055 NP -10 (Separan, Dow Chemical Co.)................ 0. 014 Nalco phosphate 519 ............................. 0.011 Nalco phosphate 936 .............................. 0.004 Staff of the Pima Mining Co. includes: P. W. Allen, general manager; A. A. Friedman, resident manager; R. E. Thurmond, assistant resident manager; J. F. Olk, mine superintendent; G. A. Komadina, mill superintendent; M. H. Nicholson, mechanical superintendent: A. G. Beebower, electrical superintendent; D. N. Tremper, office manager; M. D. Martin, chief mine engineer; J. A. Journeay, resident geologist; D. C. Shelton, metallurgist; H. E. Rudi, director of personnel and labor relations; H. E. Eckstein, purchasing agent; and G. Schuler,. safety engineer. END