How a screw compresses
A rotary screw compressor drives refrigerant vapor through the shrinking cavities between two meshing helical rotors. Gas enters at one end, the lobes carry it forward, the cavity volume shrinks, and compressed gas discharges at the other end. No valves, no reciprocating mass — just continuous rotation, which is why screws run smoother and quieter per ton than any piston machine and hold up under long, hard duty cycles.
Where screws live
Screws are the standard in mid-to-large commercial chillers — most air-cooled machines above roughly 70 tons and many water-cooled plants — plus industrial refrigeration and process cooling. A slide valve or variable-speed drive lets the compressor modulate capacity smoothly, which is exactly what a chiller spending its life at part load needs.
What they demand
Oil is the screw's lifeblood — it seals the rotor mesh, cools the compression, and lubricates the bearings. That makes oil analysis the single most valuable maintenance item on a screw machine: acid, metals, or refrigerant dilution in the sample flag trouble long before a bearing lets go. Add discharge-temperature and vibration trending, separator and filter service, and tight leak discipline, and a screw compressor routinely outlives the building's ownership.
When one goes down
A failed screw is a five-figure event, so the diagnosis has to be right: bearing failure, rotor contact, a stuck slide valve, and drive or electrical faults all present differently, and the fix ranges from a valve repair to a remanufactured exchange compressor. We self-perform chiller and compressor work across the Southeast — written findings, both repair paths priced, and an honest call when the machine is done. See our chiller troubleshooting guide for what to check before you call.