Pharmaceutical Cleanroom Pressure Differential Control Key Elements
Pharmaceutical cleanroom require maintaining a pressure difference of at least 10 Pa between rooms of different cleanliness levels. Uncontrolled pressure differences can easily lead to validation failures or quality incidents. Room airtightness is a critical factor and must be considered throughout the entire process, from design and construction to commissioning, validation, and operation and maintenance.
1. Design Phase
After confirming the room cleanliness level, the HVAC system must calculate the airflow balance according to the formula, ensuring that the supply air volume = exhaust air volume + pressure difference maintenance airflow. Three key points require attention:
(1). Sealing of holes in sandwich color steel panel: Sprinkler holes should use sprinkler heads with decorative cover plates; pipe penetrations through walls should use one of three methods: sleeves, decorative covers, or sealing devices. Sleeves are suitable for high-pressure difference workshops, decorative covers are suitable for low-pressure difference and low-cost scenarios, and high-airtightness areas require sealing devices. The solution for equipment penetrations through walls should be determined based on specific needs.
(2). Door and window selection: High-pressure difference rooms should use fixed double-glazed windows, with materials transported via transfer windows; cleanroom doors should be equipped with door closer. If high-speed roller shutter door is used as an airlock for material transfer, the airlock pressure difference should be less than 20 Pa; otherwise, the door leaf needs to be reinforced.
(3). HVAC system: Exhaust vents should use normally closed plate type vents to avoid damaging the clean surface; supply and exhaust air volumes should have sufficient margin to meet airtightness and pressure difference requirements.
2. Construction Phase
(1). Sandwich color steel panel connection: Vertical walls should use Character 中 shaped aluminum or male-female groove connections, with internal and external sealing for high-airtightness workshops; for vertical walls and ceiling panels, the ceiling panel overlapping the wall panel is preferred, with gaps treated with rounded corner decorative strips, and layout deviations controlled within 2‰.
(2). Door gap control: The door sweep strip must meet the standard, and the floor should be tested with a 2m straightedge, with a flatness deviation of no more than 2-3mm to ensure sealing.
3. Commissioning and Validation Phase
First, perform airflow balance commissioning, measure the actual airflow and adjust it to the design value, and add additional airflow to rooms with insufficient airtightness. Then, the system is run continuously for 24-48 hours to test its stability, ensuring that the pressure difference fluctuation remains within ±10% of the set value. The variable frequency response can be optimized through sensor-linked PID control, and the control strategy for the buffer zone can be adjusted. The validation process requires simulating production disturbances, with system data recorded at a sampling frequency of ≥1 time/s. Three successful tests under the worst-case conditions are considered acceptable.
4. Operation, Maintenance, and Improvement
A remote monitoring system is established, with an early warning mechanism and data archiving. Sealing points are inspected monthly, and leak detection is performed quarterly using professional equipment. Pressure-independent variable air volume valves require regular calibration and maintenance. The pressure decay method is commonly used to detect airtightness, while the tracer gas method is used in high-risk areas. A special meeting is held every six months to optimize the system and introduce new technologies to improve control levels.
Suzhou Pharma Machinery Co.,Ltd.
2026/03/09
Icey
