Liquid Ring Vacuum Pumps and Compressors for Petroleum, Chemical, and Gas Industry ServicesAPI STANDARD 681FIRST EDITION, FEBRUARY 1996REAFFIRMED, NOVEMBER 2010Liquid Ring Vacuum Pumps and Compressors for Petroleum, Chemical, and Gas Industry ServicesManufacturing, Distribution and Marketing DepartmentAPI STANDARD 681FIRST EDITION, FEBRUARY 1996REAFFIRMED, NOVEMBER 2010