The HDO is a between bearing, multistage, radially split double case barrel with an axially split double volute, opposed impeller inner case. Designed for medium and high pressure applications. In excess of thousands of units installed, the Flowserve HSO/HDO high pressure multistage barrel pump is a unique member of the double-case barrel pump family in that it is offered in both General Purpose and Special Purpose configurations. The HSO/HDO volute-style barrel pumps are manufactured to customer specifications, often exceeding API 610 (BB5).