Differential pressure air volume control is crucial to ensure the cleanliness of clean room and prevent the spread of contamination. The following are clear steps and methods to control air volume for pressure differential.
1. The basic purpose of pressure differential air volume control
The main purpose of pressure differential air volume control is to maintain a certain static pressure difference between clean room and surrounding space to ensure the cleanliness of the clean room and prevent the spread of pollutants.
2. Strategy for pressure differential air volume control
(1). Determine pressure difference requirement
According to design specifications and production process requirements of the clean room, determine whether pressure difference between clean room and surrounding space should be positive or negative. The pressure difference between clean rooms of different grades and between clean areas and non-clean areas should not be less than 5Pa, and the pressure difference between clean area and outdoor should not be less than 10Pa.
(2). Calculate differential pressure air volume
The leakage air volume can be calculated by estimating the number of room air change times or the gap method. The gap method is more reasonable and accurate, and it takes into account the air tightness and gap area of the enclosure structure.
Calculation formula: LC = µP × AP × ΔP × ρ or LC = α × q × l, where LC is pressure difference air volume required to maintain pressure difference value of the clean room, µP is the flow coefficient, AP is the gap area, ΔP is the static pressure difference, ρ is the density of air, α is the safety factor, q is the leakage air volume per unit length of the gap, and l is the gap length.
Control method adopted:
① Constant air volume control method (CAV): First determine the benchmark operating frequency of the air conditioning system to ensure that supply air volume is consistent with designed air volume. Determine fresh air ratio and adjust it to design value. Adjust return air damper angle of the clean corridor to ensure that the corridor pressure difference is within appropriate range, which is used as the benchmark for the pressure difference adjustment of other rooms.
② Variable air volume control method (VAV): Continuously adjust the supply air volume or exhaust air volume through electric air damper to maintain the desired pressure. The pure differential pressure control method (OP) uses a differential pressure sensor to measure the pressure difference between room and reference area, and compares it with the set point, and controls the supply air volume or exhaust air volume through the PID adjustment algorithm.
System commissioning and maintenance:
After the system is installed, air balance commissioning is carried out to ensure that differential pressure air volume meets design requirements. Regularly check and maintain the system, including filters, fans, air dampers, etc., to ensure stable system performance.
3. Summary
Differential pressure air volume control is a key link in clean room design and management. By determining the pressure difference demand, calculating the pressure difference air volume, adopting appropriate control methods, and commissioning and maintaining the system, the cleanliness and safety of the clean room can be ensured and the spread of pollutants can be prevented.
Post time: Jul-29-2025