They wear from the first hour. This is physics, not a defect and not a maintenance lapse. As the bearings wear, the rotors shift, the micrometric clearances open, and the internal leakage path between the rotor lobes — the blowhole — grows.
High-pressure air slips back toward the inlet. The compressor keeps running; it just delivers less air for the same kilowatt-hour, so its specific energy (kW per m³/min) quietly worsens.
Two details make this worse than a gentle, linear fade. Pressurised air drives the rotors toward the intake, producing an axial thrust held in check only by the thrust bearings — and the clearance at the high-pressure delivery end, where sealing matters most, is exactly where that wear bites hardest.
And the loss compounds: wider gaps mean more leakage, more leakage means more heat, more heat means more thermal movement.
This isn't a fringe view. It appears in the published work of the screw research community itself — the academic groups that have spent three decades optimising the technology, and a U.S. national laboratory study built specifically to detect thrust-bearing failure inside a running screw.
When the people refining a technology document its inherent leakage mechanism, that's not marketing; it's engineering reality. Independent field studies of in-service fleets have measured losses anywhere from 15% to over 50% against the original rating.
Read the full engineering case → https://www.linkedin.com/pulse/why-screw-compressor-efficiency-declines-over-time-rotary-contaldi-usqkf/