Viscous Liquid Rotary Gear Pumps

Superior Performance In Transfering Fluids

Gorman-Rupp Gear Pumps for Lubricants, Thinners, and Viscous Liquids

Gorman-Rupp’s “G Series” rotary gear pumps are capable of pumping fluids with viscosity as low as a few centistokes [cSt], up to 400,000 cSt, with temperatures up to 357° C. These pumps have been designed to last longer, operate at higher pressures, and be easier to operate than any other rotary gear pump. They are manufactured with unique features that enable them to last longer, pump higher pressures, and pump a wider variety of fluids than any other gear pumps in the industry.

How to Select the Right Gear Pump?

A gear pump is a type of positive displacement (PD) pump. It moves a fluid by repeatedly enclosing a fixed volume using interlocking cogs or gears, transferring it mechanically using a cyclic pumping action. It delivers a smooth pulse-free flow proportional to the rotational speed of its gears.

Gear pumps come in several forms. They are pumps, which are usually selected when applications call for constant flow, high pressure, high viscosities, or specialist requirements for certain fluids.

The four common types of gear pump are external gear, rotary lobe, vane pumps and internal gear pump. Depending on the application, gear pump may offer superior features over the others. All are self-priming pumps and deliver smooth pulse-less flows.

How to select the right gear pump

External Gear Pump

An external gear pump consists of two identical gears. A driven gear, “driving” another gear. The action of two rotating gears coming out of mesh at the suction side of the pump develops the vacuum that pulls liquid into the casing. Fluid on the inlet side flows into the chamber and becomes “trapped” between the rotating gear teeth and the chamber housing. The spaces between the gear teeth transport the fluid along the outer perimeter of the housing to the discharge side. Here the gears “re-mesh”, forcing fluid out the discharge.

The gears are supported on both sides, making them ideal for high pressure applications like those found in the fluid power industry.

They are however not suitable for abrasive applications [like paint and ink] because there is no end clearance adjustment, meaning a worn pump needs to be re-built rather than re-adjusted. They are also not as good on highly viscous applications [as speed must be slowed considerably].

external gear pump

Vane Pumps

A vane pump has a slotted rotor with vanes or blades fitting within these slots. The rotor is off-set inside its housing to form a crescent-shaped cavity. As the rotor rotates and fluid enters the pump, centrifugal force, hydraulic pressure, and/or pushrods push the vanes to the walls of the housing.  The tight seal between the vanes and the pump housing is the key to the good suction characteristics common to the vane pumping principle. This characteristic makes the vane pump excellent at priming and handling low viscosity liquids.

Vane pumps are also not suited to abrasive applications because [as with external gear pumps they have fixed end clearances, and once wear occurs, cannot be adjusted. They are also not as well suited to pumping viscous fluids, as speeds need to be slowed dramatically.

vane pump

Lobe Pumps

Lobe pumps usually consist of two, two, three or four-lobe rotors that rotate inside a casing. External timing gears found within a casing external to the pump chamber prevent the lobes coming in contact with each other. Pump shaft support bearings are located in the timing gearcase.

The motion developed by the rotating lobes, expands the volume on the suction inlet side of the chamber by trapping the liquid in the pockets between the lobes and the casing of the chamber. The re-meshing of the rotors on the discharge side forces liquid out of the pump.

Lobe pumps are frequently used in the food industry because of their capacity to handle large solid particles and because some can be supplied as “sanitary” pumps.

If not being used to transport solid particles, a lobe pump can be an expensive option, as the requirement for timing gears, two shafts and two mechanical seals make them an expensive option. They also have pressure limitations because of the over-hung load created by the bearings not being external to the pump chamber.

lobe pumps

Internal [Rotary] Gear Pump

A rotary gear pump use the “gear-within-a-gear” principle. A rotor gear drives an inner or idler gear which rotates on a stationary pin and operates inside the larger rotor. A stationary crescent is fitted between the outer edge of the idler gear and the inner edge of the rotor.

The gears create voids as they come out of mesh and liquid flows into the gear pump. The liquid travels between the rotor teeth “below” the crescent and between the idler gear teeth “above” the crescent.  When the gears “re-mesh” the fluid is forced out of the discharge of the pump.

Internal gear pumps are probably the most versatile of the gear pump. They are self-priming pumps, can handle thin liquids such as ammonia, solvents, alcohol and fuel through to very viscous products such as molasses, food syrups and even grease. They can also cope with abrasive and high-temperature liquids.

Although able to handle relatively high pressures [to 300 psi or 20.7 BAR], which gives them an advantage over lobe pumps and vane pumps, they can’t reach the pressures of external gear pump. They also cannot handle the solids of a lobe pump. They do however have end clearance adjustment, which allows clearances to be adjusted as the pump wears.

Rotary Gear Pump

Exclusive to Hydro Innovations
Hydro Innovations is proud to represent Gorman-Rupp in Australia. Gorman-Rupp has been revolutionizing the pumping industry since 1933, with many of the innovations introduced by Gorman-Rupp becoming industry standards. When you invest in a Gorman-Rupp product, you buy more than just a pump. You benefit from decades of research, state-of-the-art manufacturing and testing facilities, and meticulous attention to detail. You also get engineering support and parts availability for the life of your pump.

Available in Medium-Duty, Heavy-Duty and Extreme-Duty models – in cast iron, cast steel and stainless steel, G-Series pumps are versatile enough to handle virtually any pumping application and liquid type.

G Series Rotary Gear Pumps

Gorman-Rupp’s G Series line of self-priming positive displacement rotary gear pumps are designed to provide unmatched performance, serviceability and adaptability. G Series pumps are versatile enough to handle a very wide range of pumped media. They are manufactured with unique features that enable them to last longer than any other gear pumps in the industry.

G Series pumps have the most extensive range of sealing, bushing, elastomer and materials options to build bespoke pumps to suit specific applications. This makes them suitable for high or low viscosity, high or low temperature, and fluid specific materials. They are therefore suitable as a waste oil transfer pump, heavy duty viscous liquid pump, as lubrication oil pumps and as a general transfer pump.

These pumps also produce a good vacuum, so your transfer pump or oil pump can have a long suction tube, and can produce high pressures to cater for a long delivery hose.

Gorman-Rupp G Series

Longer Lasting

All G Series pumps are designed with features that are only available on Gorman-Rupp rotary gear pumps. The quality manufacturing and testing that go into each pump ensure reliable pumping long after installation. Additional features include:

Rigid Rotating Elements
Optimum bushing locations provide high-pressure operation while reducing overhung loads. On both packed box and mechanical seal models, the bushings are located as close as possible to the applied loads, providing maximum shaft support.
High-strength gear material eliminates the need for special steel-fitted pump components traditionally required for viscous applications.

Internal Seal Vent
Venting provides continuous flow of liquid through seal cavity, ensuring cooling. The seal cavity maintains low pressure, reducing seal face load and increasing seal life.

Gorman-Rupp G Series

Easy To Service

Back Pull-Out Design
The back pull-out design provides the ability to perform service and maintenance without disconnecting pump housing from piping.

Adjustable No-Leak Pressure Release Valve
Innovative O-ring design on the relief valve allows for adjustment during operation, without leakage.
Although oil transfer pumps may not need regular maintenance, it is good to know that your oil pump or viscous liquid pump can be accessed easily when required.

The pumps also have a foot bracket that is available in several heights to match the centre-line of the motors they are coupled to, and they have multiple port positions for easy integration into piping systems.

Gorman-Rupp G Series


Watch instructional videos here showing gear pump:

Rotary Gear Pump Video

Gorman-Rupp Vs. Competitor Pump

Our expert team is standing by for any questions you have about how to best configure your pump or aeration system.

Hydro Innovations is proud to distribute a broad range of quality, reliable and industry-leading industrial pumps and aerators.

We are also delighted to share that Hydro Innovations is proud to be the exclusive distributor of Gorman-Rupp Pumps.

Gorman-Rupp is the world leader in self-priming centrifugal wastewater pump technology, and invests heavily in R&D, and in training for their international representatives – like Hydro Innovations.

This puts us in an excellent position to make the very best recommendations for our Australian customers.

Our other suppliers, Ragazzini of Italy and EDUR of Germany, are also world leaders in their respective technologies (Peristaltic Pumps – Ragazzini, and Specialist centrifugal pumps – EDUR).

We carry a very large inventory of pumps and spare parts for all of these brands, to help us to deliver industry-leading service.