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Product Introduction
A 40 bar medium-pressure oil-free water-lubricated screw air compressor with 20 m³/min capacity is an advanced industrial compressed air system engineered specifically for high-demand blow molding applications. Unlike traditional oil-lubricated compressors, this system utilizes purified water as the sole medium for lubrication, sealing, and cooling—completely eliminating oil from the compression chamber.
The unit features a two-stage compression design that delivers a continuous supply of 100% oil-free compressed air at pressures ranging from 30 to 40 bar, with a flow capacity of up to 20 m³/min. This makes it the ideal power source for PET bottle stretch blow molding, where instantaneous high-pressure air (30–40 bar) is required to shape bottles with absolute purity.
Key Attributes of the 220kW Two‑Stage Screw Compressor
1. 100% Oil-Free – Class 0 Certified
The compressor uses purified water instead of oil for lubrication, sealing, and cooling. This ensures the delivered compressed air meets ISO 8573-1 Class 0 certification—the highest international standard for oil-free air. For PET bottle production, this means zero risk of oil contamination inside the bottles, which is critical for food, beverage, and pharmaceutical packaging applications.
2. Superior Energy Efficiency – Save at Least 30%
The single-screw compressor design theoretically has zero clearance volume, eliminating energy loss. Water lubrication reduces friction and enables efficient operation even at low speeds (~3,000 rpm). Compared to traditional high-pressure compressors, this unit delivers at least 30% energy savings. Additionally, compared to dry oil-free compressors, it saves over 15% more energy. The integrated Permanent Magnet Variable Speed Drive (VSD) further optimizes power consumption by automatically adjusting output to match actual demand.
3. Low Operating Temperature – Extended Service Life
Water has a high specific heat capacity and continuously absorbs compression heat during operation, maintaining compression temperatures below 50°C—close to ideal isothermal compression. This low-temperature operation: protects internal components from thermal stress, significantly reduces wear and tear, and achieves an ultra-long service life of over 50,000 hours.
4. Ultra-Quiet & Vibration-Free Operation
The rotary screw compression method eliminates the pulsation and mechanical vibration inherent in reciprocating piston designs. The machine operates so smoothly that a coin can stand still on it during operation. Noise levels are kept between 75–80 decibels—comparable to normal conversation—creating a safer, more comfortable working environment for operators.
5. Low Maintenance & Cost-Effective
With no oil filters or oil separators to replace and no oil disposal costs, maintenance is dramatically simplified. Consumable parts are limited to air and water filter elements, costing less than $500 per year. Routine maintenance is quick and infrequent, significantly reducing Total Cost of Ownership (TCO) compared to piston compressors.
6. Environmentally Friendly & Sustainable
Zero oil waste—the lubrication water can be easily drained and replaced without special treatment. The system uses food-grade stainless steel throughout, including the screw air-end casing and pipelines, ensuring full compliance with environmental and industry standards.
7. Smart PLC Control & Remote Monitoring
Equipped with an advanced PLC control system providing real-time monitoring of pressures, temperatures, and operational status. Features include cloud-based monitoring and predictive maintenance capabilities, enabling remote operation and management. The fully automated water-changing device allows lubrication water replacement without halting operations
PET Bottle Blow Molding (Primary Application)
This is the core application for this compressor. PET stretch blow molding requires instantaneous high-pressure air (30–40 bar) to shape bottle preforms. Applications include:
Bottled water and beverage containers
Carbonated soft drink bottles
Pharmaceutical packaging
Cosmetic and personal care product containers
Food-grade packaging (edible oils, sauces, condiments)
Juice and tea beverage bottles
The oil-free nature of the compressed air is non-negotiable for these applications, as any oil contamination would render the bottles unsafe for food and beverage contact.
Screw Compressor vs. Piston Compressor – Key Advantages
When choosing a medium-pressure oil-free compressor for PET blow molding, the water-lubricated screw compressor offers decisive advantages over traditional piston compressors:
| Comparison Aspect | Water-Lubricated Screw Compressor | Piston Compressor |
| Operating Temperature | <50°C – water absorbs heat, near isothermal compression | 150–180°C in compression chamber; 75–85°C discharge |
| Air Quality | 100% oil-free, ISO 8573-1 Class 0 | Potential oil carry-over; requires oil filters |
| Noise Level | 75–80 dB – smooth rotary motion | >100 dB – pulsating reciprocating motion |
| Vibration | Minimal – coin can stand still during operation-10 | High – requires heavy foundations |
| Maintenance Frequency | Low – only air/water filters (<$500/year) | High – frequent replacement of piston rings, valves, and packing. |
| Flow Capacity | Up to 20 m³/min – ideal for high-volume production | Typically 0.5–11 m³/min |
| Energy Efficiency | ≥30% energy saving-10 | Lower efficiency, higher specific power consumption |
| Service Life | >50,000 hours-10 | Shorter due to wear of reciprocating parts |
| Space Requirement | Compact – skid-mounted, small footprint- | Large – multiple units may need parallel operation |
Why Screw Compressor is the Superior Choice for PET Blow Molding
1. Unmatched Air Purity
The water-lubricated screw compressor delivers truly 100% oil-free air from the source. Piston compressors, even "oil-free" models, still have lubricated crankcases that pose a risk of oil carry-over through worn seals or failed filters. For food and beverage packaging, this difference is critical.
2. Continuous 24/7 Operation
PET blow molding lines often run around the clock. Screw compressors are designed for continuous heavy-duty operation with minimal downtime. Piston compressors, with their higher number of wear parts, require more frequent maintenance interruptions.
3. Lower Total Cost of Ownership
While the initial investment may be higher, the screw compressor delivers substantially lower long-term costs through:
30%+ energy savings
Minimal maintenance (no oil, no piston rings, no valves to replace regularly)
Longer service life (>50,000 hours)
No oil disposal costs
4. Better Working Environment
The quiet, vibration-free operation of the screw compressor creates a safer, more pleasant working environment. Piston compressors, with noise levels exceeding 100 dB, pose hearing health risks and require hearing protection for operators.
5. Scalability for Large Production
For high-speed PET blow molding lines (8 cavities or more), piston compressors often require multiple units in parallel, increasing floor space, complexity, and maintenance burden. A single 20 m³/min screw compressor delivers the required capacity efficiently and reliably.
