MACHINE FAMILY
Oil-Injected Screw Compressors
The oil is the coolant — which is why temperature barely binds it.
Oil injected directly into the compression space: it seals clearances, absorbs the heat of compression and allows pressure ratios no adiabatic machine would survive. This is a different animal from the shop-air screw compressor — it is a process machine.
The envelope
| Recommended discharge pressure | ≤ 50 bar(g) |
|---|---|
| Suction flow window | 100–30,000 m³/h |
| Pressure ratio | No ratio limit claimed by one maker; a Chinese line caps at 15:1 — treated here as a 20:1 single-stage ceiling |
| Oil-free | No — oil is in the gas path by design |
| Sealing | Oil-injected — the oil film is the internal seal; shaft seals are conventional, with an oil separator downstream |
| Wetted materials | Carbon steel, Cast iron / ductile iron, Stainless steel 316L |
| Design standards | API 619 (rotary-type positive-displacement compressors) where specified |
Where it is used
- Fuel-gas and process-gas boosting: natural gas, BOG, coke-oven gas, coal-bed methane, biogas, CO₂
- Duties with wide operating swings
- Streams where oil contact is acceptable
Where it stops
- Purity-critical gas rules it out outright — oil is in the gas path by design
- 50 bar(g) recommended ceiling; beyond that, review
- From atmospheric suction the practical ceiling is set by single-stage ratio capability, not by the pressure figure
Chinese lines publish 5.0–5.2 MPa(G); one international maker catalogues 100 bar(g).
Related reading
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