74313539
Sep 14, 1992
Nov 22, 1994
screens and screen units cleaned by fluid filtration apparatus in treatment of waste water; namely, screens for use with water injection equipment in secondary recovery of oil and gas by water flooding oil and gas bearing reservoirs by fluid backwash; screens and screen units cleaned by fluid backwash for use with water injection equipment in secondary recovery of oil and gas by water flooding oil and gas bearing reservoirs
Environmental Control Apparatus