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

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Watch instructional videos here showing gear pump:

Rotary Gear Pump Video

Gorman-Rupp Vs. Competitor Pump

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Gear Pump:

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The EDUR LBU multiphase pump is a multi-stage centrifugal pump with the unique capability of being able to pump a liquid/gas mixture. The centrifugal pump is constructed of either C.I./ Bz/ SS, Nodular Cast Iron, All-Bronze, Stainless Steel, or Super-Duplex Stainless Steel construction, so may be used to handle a variety of liquids.

Air, Oxygen, Carbon Dioxide and Ozone gases can be introduced into the suction line and transported and used to mix or disperse the gases. This makes the pump ideal for DAF plants, where the multiphase pumps provide the task of air saturation without the use of compressed air (no compressor, air saturation tank or associated controls).

Advantages include:

  • Flows to  16 l/s
  • Heads to max. 250 m
  • Operating pressure max. 40 bar
  • Handle temperatures from -50 °C to 140 °C
  • Gas contents up to 30 %
  • up to 115  cSt
  • Cast iron/Bronze/Stainless steel, Nodular cast Iron, All-Bronze, Stainless Steel, or Super-Duplex Stainless Steel construction
  • Completely replace the “old” DAF system with a single pump

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The Lampo emergency response trailer unit is designed to speed up and simplify the deployment of emergency response equipment for municipalities, emergency services and contractors.

Advantages include:

  • Enables deployment of multiple pieces of equipment, using only one vehicle.
  • Diesel-driven power generator complete with variable frequency drive [VFD] powers a lighting tower and a rugged and reliable Gorman-Rupp pump.
  • The cleverly designed unit can light up a work area while operators set up the self-priming pump or operate numerous electric tools from the power generator.
  • The VFD allows for soft starting electrical equipment, including the pump, and can vary the speeds of these machines to suit the duty at hand. While all this is happening, the compressor can be driving air nibblers, air-operated nail guns, wrenches or tyre inflators.
  • The Lampo units also come standard with an air compressor, discharge hose reel, suction hoses and a robust mounted toolbox.

The central components of the Lampo – the generator, VFD and lighting system are manufactured by quality equipment manufacturer, Euromacchine in Italy. They are housed in an acoustically rated enclosure constructed from powder-coated galvanised steel plates.

The Lampo emergency response unit are then mounted on an Australian heavy-duty built hot-dip galvanised double axle trailer and fitted with a self-priming Gorman-Rupp trash pump.

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The Gorman-Rupp G Series range of self priming positive displacement rotary gear pumps is designed to provide superior performance in the transfer of process fluids, unmatched in the industry. Available in Medium-Duty , Heavy-Duty and Extreme-Duty (abrasive service) models, pump materials include cast iron, cast steel and stainless steel.

G Series self priming pumps are manufactured with unique features that enable them to perform better and last longer on countless applications, providing quality and reliability that make the G Series the premier pump in the industry.

Advantages include:

  • An automatic idler pin lubrication system uses the pumped fluid to continuously cool and lubricate the idler pin and bush to reduce wear in this area.
  • An internal seal cavity venting system provides a continuous flow of liquid through the seal area, ensuring cooling and reducing pressure. This reduces seal face
  • load, increasing seal life.
  • A deep “end-feed” area offers superior priming performance under low inlet pressure conditions and/or high viscosity liquids.
  • Easy to service
  • Viscosities to 440,000 cSt
  • Pressures to 20.7 bar (300 psi)
  • Flows to 2200 litres per minute
  • Handle a variety of liquids , including highly viscous, high temperature and abrasive fluids
  • Widest range of sealing options in the industry
  • High strength material eliminates the need for special steel fittings traditionally needed for viscous applications.
  • Widest range of housing ports
  • Widest range of bushing materials

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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.

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