Patent ID: 7445435

Claim:
A pressure counter-balancing apparatus for a positive displacement reciprocating pump, the positive displacement pump having at least one pump outlet, the counter-balancing apparatus comprising: a balancing piston disposed in a tubular seal sleeve, wherein the balancing piston is in fluid communication with the at least one pump outlet; a pressure balancing chamber defined by the balancing piston, the tubular seal sleeve and a seal body, the pressure balancing chamber positioned opposite the at least one pump outlet to counter-balance downward pressure upon the positive displacement pump created by the hydrostatic head during pumping; and a seal housing for receiving the seal body, wherein the seal body creates a seal with the seal body and the seal body is axially movable within the seal housing along a longitudinal axis of the seal housing and wherein the seal body acts as a check valve for permitting fluid to flow out of the seal housing while substantially prohibiting the flow of fluids into the seal housing.