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.
External Gear Pumps
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.
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.
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.
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.
