Single blade dampers are no longer used because they were closed by what means?

The use of single blade dampers has decreased primarily because they were designed to be closed by gravity. When a single blade damper is in a horizontal position, it relies on its weight to seal off the airflow when it is not in use. This can lead to inefficiencies, especially if the damper is not fully sealing or if the system operates under varying pressures, which can cause the blade to remain partially open.

Moreover, single blade dampers pose challenges in terms of control and stability, as their operation is heavily influenced by the installation angle and physical factors such as vibration or air pressure changes, making them less reliable in modern HVAC systems that favor more precise and controlled airflow management solutions.

In contrast, modern dampers often use more advanced technologies, such as pneumatic or electro-mechanical actuators, which provide better control over the airflow and can be adjusted based on the system's needs, making them more effective than relying solely on gravity. This shift towards more reliable and controllable systems has led to the decline in the use of gravity-operated single blade dampers.