1. Why are the requirements for compressed air the most stringent?

In food and beverage production facilities, compressed air serves not merely as a "power source," but as the "fourth medium" that directly interacts with raw materials, semi-finished products, finished goods, and packaging—running through every stage of the production process, from mixing and blending to bottling and labeling, and from packaging to sealing. The presence of oil mist, condensate, or microorganisms in compressed air can directly contaminate products, leading to excessive foreign particle levels, shortened shelf life, or even product recalls. Consequently, international food standards such as ISBT, BRC, and IFS designate compressed air cleanliness classification as a critical audit criterion.

Key Principle: Food-grade compressed air must be 100% oil-free from the source, rather than being contaminated with oil first and then filtered.

II. How should the food-grade compressed air standard be read?

The most widely cited standard in the industry is ISO 8573-1:2010, which categorizes three types of contaminants—solid particles, moisture, and oil content—into distinct levels.

Class 0 in the table represents the highest grade, yet it is not a fixed value (not simply ≤0.003 mg/m³). Per ISO standards, Class 0 is defined as "compressed air cleaner than Class 1 (≤0.01 mg/m³)". Its specific limit values shall be measured and verified by equipment manufacturers under specified test conditions, with a complete machine test report issued accordingly. This indicates that Class 0 air quality must be achieved at the main unit of an oil-free compressor. Attempting to filter oil content from Class 2 to Class 0 using post-stage activated carbon filters carries extremely high risks during continuous production, alongside exorbitant filter element replacement costs. This is a critical red line that overseas food auditors (such as BRC/IFS auditors) pay the closest attention to.

III. Analysis of Gas Consumption Throughout the Entire Food and Beverage Production Process

3.1 Mixing & Blending

Compressed air drives pneumatic valves and mixers to achieve thorough ingredient mixing, by pneumatic transfer of syrup, concentrate, etc. from storage tanks to blending tanks. Some processes employ direct aeration stirring, requiring the gas to be 100% oil-free and odorless; otherwise, it may directly contaminate the raw solution. Gas requirements: 0.6–0.8 MPa, continuous supply.

3.2 Filling

Among the three mainstream filling processes—isobaric filling, negative-pressure filling, and atmospheric-pressure filling—compressed air not only controls the operation of the filling valve but also directly enters the bottle during isobaric filling to contact the liquid surface. The oil content must be zero, and particulate matter and moisture must be strictly controlled; otherwise, it may cause level deviation, foaming, nozzle clogging, or secondary contamination at the bottle mouth. Gas requirements include high flow rate and stable pressure, typically requiring a pre-stage adsorption dryer and sterilizing filter.

3.3 Bottle Blowing

The PET blow molding process represents the most gas-intensive stage in production lines: medium-speed machines consume 2–6 m³/min, while high-speed models exceed 10 m³/min, requiring a pressure range of 2.5–4.0 MPa. Compressed air is directly injected into the bottle mold for shaping, and oil mist adheres to the inner surface of PET bottles, visible to consumers. Oil-containing machines necessitate multi-stage activated carbon filtration, demanding frequent filter replacement and posing contamination risks. Operational requirements include high pressure, high flow rate, minimal pulsation, and zero oil content.

3.4 Packaging

Cylinders and pneumatic grippers used in processes such as labeling, capping, coding, boxing, and palletizing driven by compressed air. Although they do not directly contact the inner surface of products, excessive oil mist can contaminate the bottle appearance, resulting in poor labeling adhesion and blurred coding. Operational pressure requirements: 0.6–0.8 MPa with minimal pressure fluctuation and rapid response.

IV. The Three Key Technical Advantages for Achieving Class 0

The mainstream technical approach employs a dry, oil-free double-screw design—no oil is injected into the main chamber; multiple layers of sealing isolate the gearbox from the compression chamber; and it combines water-cooling/oil-cooling hybrid cooling with permanent magnet variable-frequency drive. Three key features:

1. Sealing and isolation: Double lip oil seal + labyrinth seal + air curtain

The dry oil-free machine maintains precise clearance between rotors through high-precision synchronous gears (AGMA Grade 13). Both ends of the main unit employ a combination of "double-lip oil seals + labyrinth seals," supplemented by micro-positive-pressure air seals that create an air barrier—forming the essential barrier for sustained oil-free operation.

2. Combined Cooling: Dual-circuit system with oil cooling and water cooling

For primary compression, a water-cooled jacket is used; for secondary compression, a combination of oil-cooled and water-cooled systems is employed. The cooling medium never enters the compression chamber throughout the process, physically preventing cross-contamination.

3. Permanent Magnet Variable Frequency Drive (PM VSD): Clean and Energy-Efficient

The blow molding machine requires pulse gas supply and stable gas flow for filling and packaging processes; traditional industrial-frequency machines continue operating at full capacity even under low loads, resulting in significant energy waste. The permanent magnet variable frequency drive dynamically adjusts speed based on real-time gas demand feedback, achieving measured energy savings of 25%–35%, while reducing operational stress on the main unit caused by frequent loading/unloading cycles and extending its service life.

V. Reference Criteria for Model Selection

When selecting equipment, it is recommended to focus on three key aspects: whether the main unit is truly 100% oil-free, whether it has obtained Class 0 practical certification, and whether its sealing structure has been long-term validated. Below are reference criteria for three typical process stages in food manufacturing facilities:

Before selecting a model, we recommend obtaining the following documents for evaluation:

· ISO 8573-1 Class 0: Actual Measurement Report on the Overall Air Output of the Device

· Cross-sectional view of the host's sealing structure

· Practical Case Studies for Food and Beverage Customers and Gas Volume Calculation Tables

VI. Conclusion

In the food and beverage industry, compressed air is evolving from a mere "power source" to a critical "process medium." A properly certified oil-free compressor not only eliminates oil contamination but also serves as the fundamental support for quality control compliance, global product distribution, and energy conservation with carbon reduction objectives.

For air source upgrades, energy-saving renovations, or new plant construction projects, please contact Huada's overseas marketing team.