An improved double-acting pump includes two fluid passages (17, 18) extending between an inlet (1) and opposite ends of the pumping cylinder (5), two fluid passages (27, 28) extending from the cylinder ends to an outlet (2), two inlet valves (11, 12) to control the flow of fluid material into the respective fluid passages (17, 18), two outlet valves (20, 21) to control the flow of fluid material from the respective fluid passages to the outlet (2), and piston means (4) for increasing and reducing the fluid pressure in the fluid passages alternately. The outlet valves (20, 21) comprise two outlet valve members urged apart by a spring (26) to engage respective axially-aligned annular valve seats (22, 23). IMAGE
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