Over the last decade, large-scale snow-making has become critical to the success of most ski areas, and compressed air is critical to make snow.

At Vermont’s Mount Snow Ski Area, water drawn from Lake Snow at the foot of the mountain is pumped to the summit. At a pressure of 240 psi, this water is delivered to several snow-making hydrants at intervals along a 33-mile piping system. The pressurized water is released to atmosphere through the hydrants' guns and atomized by compressed air at 70 to 80 psi. When ambient temperatures are below freezing, the water crystalizes into snow. The snow-making guns, which may operate around the clock, can generate up to 1 ft of snow per hour per acre.

Because the area only makes snow for three or four months a year, the ski-area operators prefer to rent their air compressors. Because local utility bills are based on peak utilization, operators prefer to rent diesel-engine driven portable machines for an estimated $100,000 annual swing in electric bills.

Portable 1200- to 1500-cfm diesel-powered, oil-free rotary screw air compressors from Atlas Copco, Wayne, N.J., had served Mount Snow for the previous four years. but when expansion and acquisition of an adjacent area required more air capacity last season, the operators found that there was no rspace for more equipment on their compressor pad. Multiple compressors, an air-collection manifold, an after-cooler, and a special cooling tower to dry the air took up all the available room.

Atlas Copco solved the space problem with its HL series 3-stage centrifugal compressor. This compressor and all support components mount within a protective enclosure on a flatbed trailer and deliver 6600 cfm — substituting for five of the rotary screw machines in half the space. As a bonus, the single diesel engine for the centrifugal package unit consumed less fuel than five smaller compressors, and saved time and effort during fueling, filter changes, and start-up.