30 Bar Oil-Free Screw Compressor | CM/G Series | 22–132 kW

30 Bar Oil-Free Screw Compressor

Two-stage oil-free rotary screw compression to 30 bar continuous duty — engineered for PET bottle blowing lines, pharmaceutical air systems, and any industrial process where hydrocarbon contamination in the compressed air supply is not acceptable.

Primary applications: PET preform stretch-blow molding · pharmaceutical packaging · food & beverage processing · electronics clean rooms · precision pneumatic systems

Product Overview

The CM/G Series is a medium-pressure oil-free rotary screw compressor designed for continuous industrial operation at 30 bar working pressure. It addresses the gap between standard utility compressors (7–13 bar) and high-pressure reciprocating units (40–350 bar). Within the 20–40 bar range, the rotary screw configuration provides better flow stability, lower noise levels, and longer service intervals than equivalent reciprocating piston designs.

Where 30 bar compressed air is required

Most factory compressed air systems run at 7–10 bar. Several processes require substantially higher pressure at the point of use:

• PET preform stretch-blow molding requires 25–40 bar high-blow air to achieve correct wall thickness distribution and crystallinity in the finished bottle. At 30 bar, the CM/G Series covers the complete pressure requirement for standard beverage and edible-oil bottle production without a separate booster stage.
• High-pressure nitrox or specialty gas blending for industrial and laboratory applications requires 30 bar feed pressure.
• Dense-phase pneumatic conveying in pharmaceutical tablet production and fine-powder food processing commonly specifies 20–35 bar to maintain product integrity over long transfer distances.
• High-pressure air bearings in optical grinding machines and precision metrology fixtures require stable supply pressure in the 20–35 bar range.
• Membrane separation systems for oxygen-enriched air or nitrogen generation operate more efficiently at elevated feed pressure.

Why the oil-free classification matters at this pressure

An oil-flooded screw compressor at 30 bar carries higher aerosol carry-over than at 7 bar because the oil-separator element operates under greater differential pressure, increasing aerosol passage rate as the element ages. In PET bottle production, oil aerosol contacting a hot preform causes surface hazing, mold fouling, and product rejection. In pharmaceutical or food applications, it creates a documented contamination event under GMP audit.

The CM/G Series eliminates this exposure by design. Oil content at the machine discharge meets ISO 8573-1 Class 0 (zero detected aerosol, liquid, or vapor) under all rated operating conditions. This classification does not depend on downstream filter element condition or replacement interval.

CM/G Series — Technical Specifications

FAD values are measured at the compressor discharge flange at 30 bar rated pressure, per ISO 1217 Annex C. Power values are shaft input at full load. Reference conditions: 20°C inlet, 1 bar(a), 0% relative humidity.

Working Principle — Two-Stage Oil-Free Screw Compression at 30 Bar

Stage 1 compression

Atmospheric air enters through a 3-stage inlet filter that removes particulate down to 3 μm. The filtered air passes through an inlet valve into the first-stage screw air end. Male and female rotors mesh with controlled clearances maintained by precision synchronizing gears — no lubricant contacts the air in the compression chamber. Rotor profiles are coated with PTFE-based or PEEK-composite material. Stage 1 compresses air from atmospheric pressure to an intermediate pressure of 5–7 bar absolute.

Intercooling

Air leaving the first stage at 150–180°C passes through a tube-and-fin intercooler. The intercooler removes heat of compression before the air enters the second stage, improving second-stage volumetric efficiency and reducing discharge temperature. A moisture separator on the intercooler outlet removes condensate discharged through an automatic drain valve.

Stage 2 compression

Intercooled air at approximately 30–50°C enters the second-stage screw air end, which compresses from 5–7 bar to 30 bar. The second air end uses the same oil-free rotor design and is housed in a gearbox isolated from the compression chamber by shaft seals and labyrinth gaps. Stage 2 discharge air exits at 30 bar and 100–140°C depending on load and ambient conditions.

Aftercooling and moisture separation

The 30 bar discharge air passes through an aftercooler that reduces temperature to within 10–15°C of ambient. A final moisture separator removes bulk condensate before the air enters the downstream distribution system. At this point the air meets ISO 8573-1 Class 0 for oil content.

Lubrication isolation

Gearbox and bearing lubrication operate in a closed circuit completely isolated from the air path. Shaft seals and labyrinth gaps between the gearbox chamber and the rotor bores prevent any oil migration into the compression stage. This isolation is what allows the machine to carry ISO 8573-1 Class 0 certification — there is no pathway by which lubricant can reach the compressed air stream.

Why Specify a 30 Bar Oil-Free Screw Compressor

Direct ISO Class 0 compliance without downstream oil removal

An oil-flooded compressor with downstream coalescing filtration can approach Class 1 oil content (≤ 0.01 mg/m³) under ideal conditions. It cannot achieve Class 0. Processes that specify Class 0 under ISO 8573-1 require an oil-free machine at the source. Oil-free classification from the CM/G Series is documented through third-party type testing and is not conditional on downstream equipment condition.

Stable pressure output across the load range

The PLC controller maintains discharge pressure within ±0.3 bar of set point throughout the operating load range. For PET blow molding, pressure stability directly affects bottle quality: variations greater than 0.5 bar at the blowing valve cause inconsistent wall thickness distribution across production runs. The CM100GV variant uses VFD motor control to maintain set pressure within ±0.2 bar even as demand shifts between cavities and cycle phases.

Continuous-duty design for industrial production environments

The CM/G Series is rated for 100% load factor — continuous operation at full capacity. Key continuous-duty design features:

• Air end rotor bearings rated for 40,000+ hours design life under normal operating conditions.
• Intercooler and aftercooler fin surface area sized for 40°C ambient temperature, not just 20°C reference conditions.
• Electronic timed condensate drains on both the intercooler separator and aftercooler separator — no manual intervention required during operation.
• PLC fault log stores the last 50 shutdown events with timestamp and sensor values for maintenance diagnosis.
• High-temperature shutdown protection at stage 1 discharge, intercooler outlet, and stage 2 discharge.

Lower total cost of ownership versus oil-flooded plus filtration

A 30 bar oil-flooded compressor paired with high-pressure coalescing and activated-carbon filters requires filter element replacement at 2,000–4,000 hour intervals. At 30 bar differential, filter elements cost significantly more than equivalent 7-bar elements. The CM/G Series eliminates the recurring filter element cost and removes the maintenance risk of running with a degraded or bypassed filter.

Water-cooled option for restricted-ventilation installations

The CM132GW variant uses a shell-and-tube water-cooled intercooler and aftercooler. This eliminates heat rejection into the machine room — relevant for installations inside a climate-controlled production building or where the compressor room has inadequate air change rate for the 132 kW heat load. Cooling water requirement: approximately 15–20 L/min at inlet temperature ≤ 32°C, with a maximum temperature rise of 10°C across the heat exchangers.

Application Areas

PET bottle blowing — primary application

PET stretch-blow molding uses compressed air in two phases. The pre-blow phase at 8–12 bar begins expansion of the heated preform. The high-blow phase at 25–35 bar completes the biaxial stretch to the final bottle shape. At 30 bar, the CM/G Series covers the high-blow pressure requirement for all standard beverage bottle formats without a booster stage.

Approximate machine sizing for PET blowing lines at 30 bar:

• 2-cavity linear blowing machine: CM22G (1.60 m³/min)
• 4-cavity linear or rotary machine: CM37G (3.00 m³/min)
• 6–8 cavity machine: CM55G (5.70 m³/min)
• 10–12 cavity high-output rotary: CM100GV (8.70 m³/min, VFD for demand matching)
• 16+ cavity or dual-machine production lines: CM132G or CM132GW (12.5 m³/min)

Pharmaceutical and medical packaging

Tablet coating systems, blister pack sealing lines, and clean-room pneumatic actuators require compressed air meeting ISO 8573-1 Class 0 for oil, Class 1–2 for particulate, and a pressure dew point of −40°C or lower for pharmaceutical GMP compliance. The CM/G Series provides the oil-free base; a 30 bar-rated desiccant dryer downstream achieves the required dew point, and 0.01 μm sterile filtration provides Class 1 particulate compliance.

Food and beverage processing

Food plants use compressed air for form-fill-seal machine actuation, product ejection and sorting, modified atmosphere packaging purging, and conveying. Where any air stream may contact an exposed food surface, ISO 8573-1 Class 0 oil content is required. The CM/G Series provides a single compressor source that can feed both the 30 bar PET blowing circuit and, through a pressure regulator, a 7–10 bar utility circuit for general plant pneumatics.

Electronics and semiconductor manufacturing

PCB assembly, semiconductor wafer handling, and display panel manufacturing rely on clean compressed air for pick-and-place pneumatics, dispensing, and clean-room pressurization. Hydrocarbon contamination causes ionic surface contamination, flux residue bonding failures, and photoresist adhesion problems. The CM/G Series meets ISO 8573-1 Class 0 for oil; a 30 bar-rated 0.01 μm coalescing filter achieves the particulate requirement.

Precision machining and air bearing applications

Air bearing spindles in optical grinding and precision turning machines require a stable, oil-free air supply at 20–35 bar. Oil contamination on an air bearing surface causes seizure and unrecoverable damage to the bearing pads. Pressure instability greater than ±0.5 bar causes bearing stiffness variation and introduces positional error in the machining process.

Compressor Selection Guide

Step 1 — Establish required working pressure

Start from the pressure required at the process inlet. Account for all pressure losses:

• Aftercooler pressure drop: 0.3–0.5 bar
• Dryer pressure drop at rated flow: 0.2–0.4 bar
• Filtration stages (per element at design flow): 0.2 bar each
• Piping distribution losses: 0.1–0.3 bar
• Load/unload control band: 1.0–2.0 bar

Each additional bar above minimum required pressure increases input power by approximately 3–5% at constant flow.

Step 2 — Calculate required FAD

FAD (Free Air Delivery) is the volumetric flow referenced to compressor inlet conditions. To convert Nm³/h to FAD:

FAD (m³/min) = [Nm³/h × (T_inlet_K / 273.15) × (1.01325 / P_inlet_bara)] / 60

After calculating peak demand FAD, add a margin of 10–15% for future process additions and ambient temperature correction.

Step 3 — Evaluate duty cycle and VFD requirement

For processes with relatively constant air demand, a fixed-speed model in load/unload mode is appropriate. For processes with variable demand, the CM100GV with VFD drive matches output to demand continuously. At 50% demand, a VFD unit saves 25–35% motor energy compared to a fixed-speed load/unload machine of equivalent rated capacity.

Step 4 — Check installation conditions

• Ambient temperature above 35°C: FAD is derated. CM132GW (water-cooled) is preferred for high-ambient installations.
• Altitude above 1,000 m ASL: Reduced inlet air density decreases both FAD and motor cooling efficiency. Request altitude-derated performance data.
• Power supply: Confirm available short-circuit current (kA) at the motor control center.
• Cooling water (CM132GW only): Confirm supply temperature ≤ 32°C and flow rate ≥ 15 L/min. Water quality: hardness ≤ 200 ppm, pH 7–9.

Frequently Asked Questions

Technical Inquiry — CM/G Series 30 Bar Compressor Selection

Submit your operating requirements using the parameters below. A compressed air systems engineer will review your application and respond with a model recommendation, performance data sheet, dimensional drawing, and suggested downstream equipment within 2 business days.

Required information

• Working pressure required at point of use — bar or psi
• Required FAD or process air consumption — m³/min, Nm³/h, or cfm
• Application description — process type and specific end-use of the compressed air
• Duty cycle — continuous, or estimated run hours per shift
• Ambient temperature range at installation site — °C or °F
• Installation altitude — meters or feet above sea level
• Air purity requirement — oil class, particulate class, pressure dew point (if specified)
• Power supply available — voltage, phase, frequency
• Cooling preference — air-cooled or water-cooled (if applicable)