Low-flow pump-off control

Abstract

A low-flow pump-off control device for deactivating a motor for a pump during conditions when a rate of supply of a source of fluid to be pumped by the pump is insufficient includes: a pipe section having an inlet and an outlet, the inlet being connectable to the source of fluid to be pumped through the pipe section; a plurality of plates disposed substantially perpendicularly in the pipe section, each of the plates defining at least one orifice through which the fluid is caused to pass; a differential pressure switch for sensing a differential pressure between a pressure upstream of a first one of the plates and a pressure downstream of a last one of the plates that is at or below a set point indicative of a predetermined low flow rate of the liquid; a first timer in communication with the switch for accumulating periods of time at which the switch senses the differential pressure; a motor activation and deactivation relay in communication with the timer for deactivating the motor when the accumulated periods of time total a predetermined amount; and a second timer in communication with the first timer which is activated when the accumulated periods of time total the predetermined amount, wherein the motor activation and deactivation relay is in communication with the second timer and activates the motor when the second timer times a second predetermined amount of time.

Dependencies are inferred from the claim text.