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"The action does not differ in any way from that of the piston force pump. During the up stroke of the plunger, the suction valve is open and the delivery valve is closed; during the down stroke, the suction valve is closed and the delivery valve is open." —Hallock 1905

Plunger Pump

"The action does not differ in any way from that of the piston force pump. During the up stroke of the…