An oil-air lubrication system delivers a continuous, metered stream of oil carried by compressed air to high-speed bearings, spindles, and gear drives — providing cooling and lubrication simultaneously with minimal oil consumption. This guide explains how oil-air technology works, where it outperforms grease and oil-mist, and how to size a system for your machinery.
What Is an Oil-Air Lubrication System?
In an oil-air (also called oil + air or油气) system, a pneumatic or electric pump feeds small, precise quantities of oil into a mixing valve, where compressed air carries the oil as a fine, continuous stream — not a wet mist, but a streak of oil moving along the pipe wall — directly to each lubrication point. The air stream also cools the bearing and creates positive pressure that keeps dust and coolant out.
Because the oil is delivered continuously in micro-quantities rather than periodically in shots, high-speed bearings run cooler, cleaner, and longer than with grease packing or bath lubrication.
Oil-Air vs Grease vs Oil-Mist: Which One Fits?
| Factor | Oil-Air | Grease (centralized) | Oil-Mist |
|---|---|---|---|
| Best for | High-speed spindles, rolling-mill bearings, gear drives | Low-to-medium speed bearings, pins, bushings | Large bearing banks, continuous casters, enclosed housings |
| Cooling effect | Strong (continuous airflow) | None | Moderate |
| Oil consumption | Very low (metered micro-dosing) | Low | Low |
| Bearing speed capability | Very high | Moderate (NLGI-dependent) | High |
| Sealing / contamination protection | Positive-pressure air barrier | Relies on seals | Positive-pressure mist |
| Typical system | Single-line or dual-line oil-air station + mixing valves | Progressive or dual-line grease system | Oil-mist generator + distribution headers |
Where Oil-Air Systems Are Used
- Steel and rolling mills — work-roll and backup-roll bearings running under heat, scale, and water spray
- High-speed spindles — machine-tool and grinding spindles where grease would churn and overheat
- Mining and cement equipment — conveyor pulley bearings, crusher bearings in dusty atmospheres
- Gear drives and pinions — targeted oil streams for tooth flank lubrication
- Chain and wire-rod lines — continuous lubrication without fling-off
System Components
A complete oil-air installation typically consists of:
- Oil-air supply station — reservoir, pump, filtration, and pressure regulation in one skid; single-line, dual-line, and pressure-relief configurations cover different plant layouts
- Oil-air mixing valves / distributors — meter each outlet’s oil quantity and blend it with the air stream; available in multiple outlet counts to match point counts
- Air preparation (FRL) — clean, dry, regulated air is essential; moisture and oil carryover from the plant air line are the most common causes of mixing-valve failure
- Piping — small-bore nylon or copper lines sized so the air stream carries oil along the tube wall to each point
- Monitoring — pressure switches, flow indicators, and low-level alarms that warn before a bearing runs dry
Sizing Basics: What to Specify
- Number and type of lubrication points — bearing bore, speed (rpm or dn value), and load decide the oil quantity per point
- Oil viscosity — typically ISO VG 32–220 depending on speed and temperature; higher speeds favor lower viscosities
- Air supply — pressure and flow available at the machine; continuous duty requires clean, dry air
- Line lengths — long runs may need larger tubing or satellite mixing stations to keep response times short
- Environment — heat, water spray, and dust determine enclosure rating and filtration level
IsoHiTech Oil-Air Options
IsoHiTech supplies complete oil-air lubrication packages and components:
- Oil-air supply stations — single-line, dual-line, and pressure-relief configurations, sized by point count and line length (standard and custom builds, available on request)
- Oil-mist lubrication systems — for plants standardized on mist technology, see our oil-mist lubrication category and the FF series oil-mist system (0.035–0.5 MPa working pressure, adjustable oil output, 7L/19L reservoirs)
- Grease spray valves — for targeted grease spraying applications, see the PF-200 grease spray valve
- Deep-dive reading — Oil Mist Lubrication: Principles, Benefits & Implementation Guide (now includes a dedicated oil-air and high-speed spindle section)
Not sure whether oil-air, oil-mist, or grease is right for your machine? Send us your bearing types, speeds, and environment — our engineers will recommend a configuration and quote a complete station.
Frequently Asked Questions
What is the difference between oil-air and oil-mist lubrication?
Oil-mist suspends oil droplets in air and works best for enclosed housings and large bearing banks. Oil-air moves oil as a continuous stream along the pipe wall to each point, giving more precise per-point dosing and stronger cooling — the usual choice for high-speed spindles and rolling-mill bearings.
What oil viscosity does an oil-air system use?
Typically ISO VG 32–220, with high-speed spindles favoring VG 32–68. High-speed spindles favor lower viscosities; heavily loaded low-speed bearings favor higher ones.
Does an oil-air system need special compressed air?
Clean, dry, regulated air is required — typically through an FRL unit at the machine. Water or oil carryover in the air line is the most common cause of mixing-valve problems.
Can oil-air replace grease on existing bearings?
In many cases yes, especially where grease churning limits speed or where cooling is needed. Retrofitting requires a supply station, mixing valves, and small-bore piping to each point — bearing housings usually need no modification.
How many points can one oil-air station serve?
It depends on the station size and per-point oil demand. Systems range from a few spindle points up to hundreds of rolling-mill bearings; share your point count and line layout and we will size the station accordingly.
Before you buy: read our central lubrication system guide.