Patent ID: 7131454

Claim:
A system to inject a secondary fluid into a primary fluid, comprising: a fluid powered motor driven by a primary fluid stream; a liquid additive injection pump driven by the fluid powered motor; said liquid additive injection pump having (a) a reciprocating piston movable within a cylinder between upstroke and downstroke positions to meter a secondary fluid; and (b) a piston sealing mechanism movable with the reciprocating piston and comprising spaced-apart distal and proximal sealing elements, said distal sealing element being flared in the direction of piston downstroke and the proximal sealing element being flared in the direction of piston upstroke; wherein the liquid additive injection pump includes a piston rod, and the spaced-apart distal and proximal sealing elements are carried thereon; and further wherein the piston rod includes first and second circumferential grooves and first and second retainer rings, said first retainer ring bearing against the distal sealing element during piston downstroke to apply a force that urges the distal sealing element against the cylinder and the second retainer ring bearing against the proximal sealing element during piston upstroke to apply a force that urges the distal sealing element against the cylinder.