A water-injected screw air compressor replaces lubricating oil with purified water inside the compression chamber. Water serves three functions simultaneously — sealing the rotor clearances, cooling the compression heat, and lubricating the moving parts. Because no oil ever enters the compression chamber, the discharged air contains 0 ppm oil content, meeting the strictest ISO 8573-1 Class 0 purity standard. This makes the water-injected screw compressor the preferred choice for pharmaceutical, food, semiconductor, and precision manufacturing industries where even trace oil carryover is unacceptable.
RAYDAFON water-injected screw compressors use a single-screw air end composed of a main screw and two symmetrically arranged flat star wheels that form a meshing pair. These components are housed inside a 304 stainless steel shell. The screw groove, the shell inner wall, and the star wheel tooth surface together create the compression chamber.
Ambient air passes through the air filter and enters the screw groove through the suction port. The motor directly drives the screw shaft at approximately 3,000 RPM, which in turn rotates the star wheels. As the screw rotates, the chamber volume decreases and the air is compressed.
Purified water is injected through spray holes on the air end shell directly into the compression chamber. The water absorbs compression heat instantly, keeping the discharge temperature at approximately 45°C. This near-isothermal process dramatically reduces energy consumption compared to adiabatic compression.
The water-air mixture flows into a stainless steel gas-water separator. Water settles to the bottom while the oil-free compressed air discharges from the minimum pressure valve at the top. The separated water is then cooled by a water cooler or air cooler and recirculated to the air end for the next compression cycle.
The closed-loop water system means no water is consumed during normal operation — only a small amount of makeup water is needed to compensate for evaporation. No oil is added at any point, and no oil-water separator or condensate disposal is required.
| Parameter | Specification |
|---|---|
| Oil Content | 0 ppm (ISO 8573-1 Class 0) |
| Compression Type | Single-screw, water-injected |
| Wetted Material | 304 food-grade stainless steel (standard); 316L optional |
| Discharge Temperature | ≈45°C (near-isothermal compression) |
| Air End Speed | 3,000 RPM (direct coupling, no gearbox) |
| Drive Method | Direct coupling between air end and motor |
| Maintenance | Air filter + water filter replacement only |
| Voltage | 220V / 380V / 440V (customizable) |
| Certifications | TÜV Oil-Free, FDA, GMP, CE, ISO 9001 |
The choice between an oil-lubricated and a water-injected compressor affects far more than the initial purchase price. Oil-lubricated systems require oil changes, oil filters, oil-water separators, and condensate disposal — recurring costs that accumulate over the compressor's entire service life.
Water-injected oil-free screw compressors are essential wherever compressed air contacts products directly or must meet strict purity specifications. The 3-column grid below covers the most common deployment scenarios.
Compressed air is used to stir, convey, and dry raw pharmaceutical ingredients. Because air contacts drugs directly, oil content, bacterial content, and dust content must comply with GMP requirements. Water-injected compressors meet ISO 8573-1 Class 0 and Class 1 purity. See pharma applications →
Direct-contact air in pneumatic conveying, packaging, and fermentation must be free of oil contamination. The 304 food-grade stainless steel wetted parts and 0 ppm oil content satisfy FDA requirements for food-grade compressed air. See food applications →
Circuit board cleaning, SMT assembly, and cleanroom pneumatic systems require pure air to avoid microscopic oil deposits that cause electrical defects. ISO Class 0 air protects high-value components from contamination. See electronics applications →
Medical oxygen generation, dental chairs, and hospital pneumatic systems require oil-free air to protect patient safety. Water-injected compressors eliminate the risk of oil carryover into breathing air circuits. See dental applications →
Air-jet looms, texturing machines, and chemical fiber production lines use compressed air that directly contacts fibers. Oil contamination causes dyeing defects and reduces product quality. 0 ppm air protects fiber purity.
Precision instruments, analytical equipment, and laboratory pneumatic systems require contaminant-free air. Water-injected compressors provide a stable, oil-free air source without the maintenance burden of oil filtration systems.
| Application | Recommended Configuration | Key Requirement |
|---|---|---|
| Pharmaceutical / GMP production | Water-injected screw + sterile filter | ISO 8573-1 Class 0 / Class 1 |
| Food & beverage direct contact | Water-injected screw + food-grade dryer | FDA compliant wetted materials |
| Semiconductor cleanroom | Water-injected screw + desiccant dryer | -40°C PDP + 0 ppm oil |
| Medical oxygen generation | Water-injected screw + PSA oxygen system | Zero oil carryover |
| General oil-free workshop air | Water-injected screw standard configuration | ISO Class 0 + 45°C discharge |
Pricing depends on flow capacity, working pressure, voltage configuration, and material selection. Share your application requirements and RAYDAFON will respond with a factory-direct quote within 12 hours.
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