June 2006 – Space technology for down-to-earth gas-pumping applications is now available in a new semi-hermetic scroll vacuum pump/compressor from Air Squared. It is available in a variety of materials, with appropriate seals, that allows it to handle almost any gas other than air, including radioactive material, bio-hazardous gases, helium, nitrogen, oxygen, natural gas and other corrosive and hazardous gases. The vacuum pump/compressor is ideal for medical and bio-medical applications, fuel cells, natural gas boosters, and handling of radioactive materials. A full-hermetic design is also available.
Originally developed to pump helium for a space-based cryo-cooler, the new semi-hermetic scroll features a unique, patent pending design that completely seals the pumping section of the unit, but allows cooling of both scrolls. Cool operation enables the unit to operate effectively at higher pressures and vacuums.
As a compressor, the unit can develop up to 60 psig (4 barg) and has a displacement of 2 CFM (57 lpm). The vacuum model can develop up to 200 mtorr ultimate vacuum, with a displacement of 2 CFM (57 lpm). AC or DC motors can be supplied.
Air Squared's patented coating technology for the scrolls allows the unit to run at volumetric efficiencies greater than 80%, or produce higher ultimate vacuums. The wetted surfaces of the unit are constructed of stainless steel, nickel, and hard anodized aluminum. All stainless steel and nickel construction is available for corrosive gasses. Standard seals are PTFE composite, with other materials, such as polyimide, available to withstand specific gases.
The rotary scroll design provides quiet, balanced, pulse-free operation with a noise level of just 50 dBa. Scroll compressors use true rotary motion, so they can be dynamically balanced for nearly vibration-free operation. Power delivery is continuous, which virtually eliminates pulsation and associated noise. There are only two primary moving parts, with no inlet or discharge valves to break or make noise, and no associated valve losses.
The operating element of a scroll compressor is made up of two identical involutes, which form right- and left-hand components. One scroll is indexed or phased 180 degrees with respect to the other to allow the scrolls to mesh. This indexing creates crescent shaped gas pockets, bounded by the involutes and base plates of both scrolls.
In operation, one scroll remains fixed; the other is attached to an eccentric driven by the motor shaft. As the moving scroll orbits around the fixed scroll, the pockets formed by the meshed scrolls at the outer edge follow the spiral inward and shrink in size. Gas entering the scroll is trapped in two diametrically opposed pockets and compressed as the pockets move toward the center, where the discharge port is located.