Gear Pump

Overview

An external gear pump is a positive-displacement pump in which two meshing gears trap fluid between their teeth and the casing wall and carry it from suction to discharge. Because each revolution displaces a fixed volume, flow is steady and nearly independent of discharge pressure, which suits the pump to metering, fuel and lube transfer, and pumping viscous oils. The tight running clearances make it most efficient on clean, lubricating fluids. This unit is close-coupled to an electric motor through a flexible coupling.

Construction

Fluid is contained by the Pump Casing: a figure-eight cast-iron body bored for the two gears, closed by front and rear end covers carrying the shaft bushings, with pressure-balanced wear plates sealing the gear faces. The pumping element is the Gear Set, a drive gear and a free idler gear running on hardened shafts in sintered-bronze journal bushings. As the gears unmesh on the suction side they create the void that draws fluid in; the teeth carry it around the casing wall and squeeze it out as they remesh on the discharge side.

Where the drive shaft exits the casing it is sealed by the Shaft Seal, a rotary lip seal running on a replaceable hardened sleeve. To protect the pump and piping against overpressure or a blocked line, an integral Relief Valve cracks open above its setpoint and recirculates flow internally. Torque comes from the Electric Motor, a TEFC induction motor, joined to the pump by a flexible Flexible Coupling that tolerates minor shaft misalignment. The assembly is footed to a baseplate on a Mounting Foot and held together with a matched Fastener Set.