Original: They operate more smoothly , quietly , and reliably than other types of compressors in the lower volume range Often , one of the scrolls is fixed , while the other orbits eccentrically without rotating , thereby trapping and pumping or compressing pockets of fluid or gas between the scrolls .
Simplified: They operate more smoothly , quietly , and reliably than other types of compressors . Often , one of the scrolls is fixed , while the other orbits eccentrically without rotating , thereby trapping and pumping or compressing pockets of fluid between the scrolls .