Machine Design

Precision gears Cut Pump Noise

High-pressure pumps run smooth and quiet.

Cesare Angeloni
Settima Flow

Edited by Kenneth Korane

Continuous-contact pumps feature helical gears that do not trap fluid as they rotate, as is the case with conventional gear pumps. This minimizes pressure ripple and gives high efficiency and quiet operation at speeds to 5,000 rpm.

Lab tests for pressure-ripple and noise show impressive improvements in pulsation and noise curves for continuous-contact pumps, while maintaining high efficiency. Pulsation tests were conducted at 100 bar, 1,500 rpm, and pressure sampling at 100 kHz. Pressure level for all pumps in the noise test was 150 bar.

It's generally accepted that OEMs are under the regulatory gun to reduce noise and vibration from machines they make. And hydraulic pumps, especially high-pressure ones, often generate noise and vibration at levels increasingly unacceptable for new applications.

Noise stems from two sources. Pumps themselves generate mechanical noise. But they also produce pressure pulsations, or ripples, amplified by tubing and structures attached to the pump. Pressure pulsations also waste energy, reduce efficiency, and can shorten the lives of pipe and hose.

To date, the only practical solution has been to house pumps in expensive enclosures, use hoses instead of pipe or tubing, and add attenuators. A new type of pump eliminates this "bandaid" approach and abates noise at the source.

The Continuum line of continuous-contact pumps combines high pressure and flow with low pulsations and noise. It's based on a special rotor profile and a design that balances internal forces.

Conventional, high-pressure gear pumps are noisy because they trap and compress fluid between gear teeth as it rotates. The result is a sharp pressure rise that generates noise — especially above about 1,500 rpm.

Screw pumps, on the other hand, almost completely over-come the oil-encapsulation problem by moving oil along a parallel path, instead of one perpendicular to the axes as the pump rotates. Screw pumps typically run silently with low pulsations, for low to medium, but not high-pressure duty. Few screw pumps are rated for pressures exceeding 40 bar.

Continuous-contact pumps, such as the Continuum, rely on meshing methods that make it a hybrid of gear and screw pumps. The pumps generate flow perpendicular to the axes, like classic gear pumps, but special helical gears do not trap fluid. Instead, there is continuous rolling contact between rotors.

The Continuum design eliminates compressed oil between gears, yielding smooth pressure changes, high efficiency, and quiet operation at speeds to 5,000 rpm. Noise levels range from 52 to 68 dBA at 2,750 rpm, based on ISO 4412 testing.

The pumps are available in various sizes with operating speeds from 700 to 3,600 rpm, displacements of 9 to 264 liters/min (@ 1,500 rpm), operating pressures of 240 bar (continuous) and 280 bar (peak), and an operating temperature range of 15 to 60°C. Pump bodies are extruded aluminum alloy with case-hardened, ground steel gears.

Settima Flow Mechanisms,

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