What are the differences between Venturi valves and conventional electric dampers: How to select variable airflow exhaust fans for laboratories
In laboratory exhaust systems, dampers are not just for switching; they must maintain the airflow of each fume hood at the set value even under frequent movement of the sight glass, startup and shutdown of other fume hoods, and continuous changes in network pressure. There are two common types of equipment to accomplish this task: Venturi valves that automatically balance pressure differences through mechanical structures, and standard electric dampers driven by controllers to adjust the opening via electric actuators. Both can regulate airflow, but their principles, response, and applicable scenarios differ significantly.
How Venturi Valves Stabilize Airflow
Venturi valves have a valve core and elastic elements inside that act with pressure difference. When the pressure difference across the valve remains within a certain range, the valve core automatically adjusts its opening to keep the airflow at the set position, achieving pressure-independent regulation through mechanical balance. It responds quickly and is insensitive to network pressure fluctuations. When multiple fume hoods start or stop simultaneously, the airflow in each branch is less likely to interfere with each other.
Changing the set airflow can be done manually via a positioner or by pairing with pneumatic or electric actuators, working with variable airflow controllers to adjust based on sight glass opening. The valve body has certain requirements for installation straight pipe sections, installation direction, and maintenance space. Its cost is higher than that of standard dampers and is often used in variable airflow systems with high requirements for airflow stability and response speed.
How Standard Electric Dampers Regulate
Standard electric dampers are driven by controllers to rotate the valve vane and change the opening based on airflow or face velocity signals, with continuous correction through actual feedback, which belongs to closed-loop control. They have a straightforward structure, lower cost, and a wide variety of options, making them commonly used in constant airflow systems and scenarios with general response requirements.
Its regulation effect is influenced by the controller algorithm, actuator speed, and network pressure. During pressure fluctuations, it requires a detection and correction process, with a slower response compared to mechanical self-balancing. There is usually a gap between the vane and the valve body, and standard regulating types do not have tight shut-off capabilities. When isolation is needed, a closed-type damper with a soft seal should be selected.
How to Choose Based on Scenarios
Venturi valves are suitable for chemical and pharmaceutical laboratories with a large number of fume hoods, frequent sight glass adjustments, rapid and constant face velocity requirements, and significant network pressure fluctuations. Standard electric dampers paired with reliable controllers can also meet the needs in scenarios with fewer fume hoods, stable conditions, primarily constant airflow or simple frequency variation, and cost sensitivity. When selecting, provide the system type, airflow range, pressure difference conditions, and corrosion-resistant flame-retardant requirements in one go, and have the ventilation design perform unified calculations to avoid choosing based solely on the valve unit price.
