Cleanroom differential pressure control systemThe complete control method

　　Cleanroom differential pressure control systemThe core goal is to maintain a stable pressure difference between the cleanroom and the surrounding environment (such as non clean areas, outdoors) or different areas within the cleanroom, in order to prevent the invasion or diffusion of pollutants. The control methods are systematically summarized from four dimensions: technical principles, control strategies, equipment linkage, and optimization methods

1、 Basic control methods

1. Mechanical air volume balance control

Principle: Maintain pressure balance by adjusting the ratio of supply air, return air, and exhaust air volume.

Formula: Δ P ∝ (Q_ send Q_ return Q_ discharge) ²

(Δ P is the pressure difference, Q is the air volume)

Implementation method:

Manual regulating valve: Install a manual air valve on the return or exhaust branch pipe to balance the air volume by manually adjusting the opening.

Residual pressure valve: Install a residual pressure valve on the enclosure structure of the clean room, which automatically opens to release pressure when the pressure difference exceeds the set value.

局限性：

Low adjustment accuracy, relying on manual experience;

Unable to respond in real-time to dynamic changes (such as door opening and closing, filter blockage).

2. Automatic control of electric air valve

Principle: The opening of the air valve is driven by an electric actuator, and the air volume is adjusted in real-time based on sensor feedback.

Implementation method:

Constant Air Volume (CAV) control: The supply air volume is constant, and the pressure difference is maintained by adjusting the opening of the return or exhaust valve.

Variable Air Volume (VAV) control: dynamically adjust the supply air volume based on pressure differential feedback, while matching the return/exhaust air volume.

Advantage:

Fast response speed and high accuracy (up to ± 1Pa);

Cleanrooms suitable for dynamic load changes, such as pharmaceutical workshops and laboratories.

2、 Intelligent control strategy

1. PID closed-loop control

Principle: By using proportional (P), integral (I), and derivative (D) algorithms, the air valve opening or fan frequency is automatically adjusted based on the pressure difference deviation.

Implementation steps:

Set target pressure difference (e.g.+10Pa);

Real time measurement of actual pressure difference by sensors;

The PID controller calculates the deviation and outputs the control signal;

Adjust the air valve or fan of the actuator until the pressure difference stabilizes.

Optimization direction:

Introduce adaptive PID parameters to cope with different operating conditions;

Combining feedforward control (such as predicting the impact of door opening and closing on pressure difference).

2. Model Predictive Control (MPC)

Principle: Establish a clean room air flow model, predict future pressure difference changes, and optimize control strategies in advance.

Application Scenario:

Multi zone pressure differential collaborative control (such as clean corridors and buffer rooms);

Complex airflow organization (such as mixing unidirectional and non unidirectional flows).

Advantage:

Reduce overshoot and improve stability;

Reduce energy consumption (such as optimizing fan frequency).

3、 Equipment linkage and redundancy design

1. Key equipment linkage

Fan valve linkage:

The frequency of the air supply fan is synchronously adjusted with the opening of the air supply valve to avoid conflicts in air volume;

The exhaust fan is linked with the exhaust valve to ensure stable exhaust volume.

Filter status monitoring:

Monitor the resistance of the filter through a differential pressure sensor, and automatically alarm and adjust the air volume compensation when the resistance exceeds the threshold.

2. Redundant control strategy

Backup sensor: automatically switches to the backup sensor when the main sensor fails;

Manual automatic switching: When the control system fails, the air valve can be manually adjusted to maintain the basic pressure difference;

Emergency pressure relief: In case of a fire, use a quick release valve to protect personnel safety.

4、 Optimization and maintenance methods

1. Dynamic calibration and compensation

Seasonal compensation: Adjust the air supply volume based on outdoor temperature and humidity (such as increasing the air supply volume when the humidity is high in summer);

Door opening and closing compensation: the infrared sensor detects the door status, and adjusts the air volume in advance to offset the pressure difference fluctuation when opening the door.

2. Regular maintenance and verification

Airflow balance test: retest and adjust the air valve opening every quarter or half a year;

Sensor calibration: Calibrate pressure sensors annually to ensure accuracy;

System simulation verification: Optimize airflow organization through CFD (Computational Fluid Dynamics) simulation.