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Purification laboratory pressure difference control method

Jun 05, 2019

Differential pressure control is a very important part in purifying air conditioning systems. Purification and process requirements can only be achieved by controlling the pressure differential in the purification zone to ensure a reasonable airflow organization. Today, Hongshuo will talk to everyone about the laboratory pressure difference control method.

For the differential pressure control system, the result achieved is essentially the control of the infiltration or seepage of the air, and its control strategy can be divided into passive and active control.

Constant Air Volume (CAV) is a passive control method that uses a manual air volume control valve to achieve a simple air supply and exhaust air balance. The air supply is less (or more) than the exhaust air (amount of residual air). The desired pressure difference. Care must be taken when selecting a control strategy such as constant air volume, as the fixed air volume system has outstanding limitations. The main points are as follows:

(1) The equipment must maintain a constant supply air volume and exhaust air volume at all times.

(2) There must be no increase or decrease in the exhaust equipment (such as biosafety cabinets), and the flexibility is poor. Future expansions will be limited due to system capacity limitations.

(3) It must be designed according to full load, and there should be a large margin to make up for the performance degradation of the air supply and exhaust system caused by filters, etc. Continuous full-load operation makes energy consumption extremely high, so the running cost is very high. . (4) Due to the performance degradation of the fan system, filter system, etc. or the change of the position of the damper, the system often needs to re-combine the wind balance and requires a lot of maintenance.

(5) Since the wind is running at all times, the noise is too high. Therefore, if the above limitations cannot be accepted, such a control strategy should not be selected. At present, by adopting a constant air volume system of a pressure independent type constant air volume control device (such as a Venturi valve) on the air supply duct and the exhaust duct, the flow can be actively and dynamically adjusted to a certain extent, and the static pressure fluctuation of the system can be eliminated. The resulting impact on the flow, thus ensuring constant flow and stable control.

Variable Air Volume System (VAV) is an active pressure control strategy that continuously adjusts the amount of air or exhaust air through an electric air volume control valve to maintain the desired pressure. Active VAV pressure control methods can be divided into two types: pure differential pressure control (OP) and residual air volume (also known as flow tracking) control (AV).

A certain degree of control over the infiltration or seepage of air. The laboratory pressure difference is also controlled. I hope this article can help you.