METHOD AND APPARATUS FOR METERING INJECTION PUMP FLOW

A system for metering a fluid, such as a catalyst in an industrial chemical process plant, includes a controller, a drive pump assembly and an injection pump assembly. The drive pump assembly forces reciprocation of the injection pump assembly via a controlled flow of hydraulic fluid. The injection pump assembly includes a drive cylinder and at least one injection section. The drive cylinder receives pressurized fluid from the drive pump assembly and causes metered fluid to be drawn into and expelled by the injection section. The position of reciprocating components of the injection pump assembly is detected between stroke limits and converted to a velocity signal. Closed-loop control of the flow from the injection pump assembly is implemented by the controller via the drive pump assembly based upon the actual velocity of the reciprocating components of the injection pump assembly and a commanded velocity. The closed-loop injection rate control may be incorporated in a nested fashion with a process parameter control loop to maintain a desired level of a process parameter, such as temperature in a reaction vessel.