Rotary Screw Compressors for Pharmaceutical Manufacturing

Where compressed air is used in pharmaceutical production

Compressed air appears at more points in a pharmaceutical plant than most process engineers first assume. Product-contact use includes powder transfer, tablet coating, fluid-bed drying, filling and packaging where air may touch the drug substance or excipient. Non-contact use covers blow-off of containers and closures, cleanroom and laboratory air, and process instrument air for pneumatic valves, actuators and dampers. Each point carries a different risk level, and that risk level should drive the specification.

Why oil-free compression matters

Where air may contact product, oil carryover is a contamination risk that cannot be corrected downstream by filtration alone. An oil-free compressor removes the lubricant from the compression chamber, so the air stream starts with no oil to remove. A Class 0 claim under ISO 8573-1 means the equipment has been tested to a defined limit, not that oil is physically absent. ISO 8573-1 defines purity by three separate classes for particles, water and oil, expressed as a three-digit string such as 1.2.1. A Class 0 oil result is a verified performance level, and it only holds for the operating conditions tested.

• Class 1 oil: 0.01 mg/m3 maximum
• Class 2 oil: 0.1 mg/m3 maximum
• Class 3 oil: 1 mg/m3 maximum
• Class 0: tighter than Class 1, verified by test, not a fixed number

Dryers, filters and the real purity class

The compressor alone does not deliver a purity class. The dryer and filter train determine the water and particle results. Refrigerated dryers typically reach a pressure dew point around +3 C, which suits general plant and instrument air. Desiccant dryers reach -40 C or lower, which is usually required for product-contact air, hygroscopic powders and cold cleanrooms. Filters add pressure drop and must be sized for the flow, not just the connection.

• Refrigerated drying: +3 C pressure dew point, lower capital and energy cost
• Desiccant drying: -40 C or lower, higher purge loss and regeneration energy
• Coalescing and sterile filters: remove particles and microorganisms, add pressure drop

Validation, qualification and change control

In a regulated environment the air system is documented, not just installed. Expect to qualify the installation, operation and performance of the compressor, dryer and filters, and to keep test records for particle, dew point and oil results. Any change to a filter element, dryer type or set point should go through change control, because it can alter the delivered purity class. Sampling points should be located where the air is actually used, not only at the compressor outlet.

Contamination control in the compressor room

The compressor room is part of the cleanroom boundary in practice. Intake air should be drawn from a clean area away from dust, solvent vapours and exhaust. Oil-lubricated compressors serving non-critical duties should be physically separated from oil-free units. Condensate must be drained and treated, and the room kept under positive pressure where possible.

Redundancy and the cost of over-treating

If the air supply stops, an in-process batch may be lost, so critical lines often use duty and standby compressors with automatic changeover and buffer storage. But treating every point to product-contact purity wastes energy. Over-drying to -40 C where +3 C is acceptable, or adding filters a packaging blow-off does not need, raises pressure drop and power consumption continuously. Match the purity class to the point of use, and let the critical points justify the cost.

Kaishan engineers can review your points of use, required ISO 8573-1 classes and redundancy needs, and recommend a matched oil-free compressor, dryer and filtration package.