Machine Design

Rotating scroll powers compressor

Vacuum pumps and compressors from Air Squared Mfg., Broomfield, Colo. (airsquared.com), handle almost any gas, including oxygen, natural gas, helium, nitrogen, and radioactive materials, but not air.

They use a semi-hermetic scroll design with two involute spirals 180° out of phase and meshed together. As one spiral orbits the other, pockets of gas between the spirals shrink, thus compressing the gas. Porting provides inlet and discharge, so there are no valves. Balanced rotary motion generates little vibration or noise, even when the compressor runs at up to 3,450 rpm. And with only two moving parts, reliability is good.

As a compressor, the unit develops up to 60 psig and displaces 2 cfm. The vacuum version develops up to 200 mtorr ultimate vacuum and also displaces 2 cfm. The device can be powered by an ac or dc motor.

A patented coating lets the scrolls run at volumetric efficiencies of 80%. Wetted surfaces are stainless steel or nickel for use with corrosive gases, and can also be anodized aluminum for other gases. Seals are PTFE, but other materials, such as polyamide, are available to handle specific gases.

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