What Is a Positive Pressure Damper?
A positive pressure damper is a device for regulating the internal pressure of a clean room or similar.
It is sometimes also called a differential pressure damper or relief damper. Positive pressure dampers are used to maintain positive pressure in clean rooms.
The installation of a positive pressure damper adjusts the differential pressure between the clean room and the outside and maintains a constant positive pressure inside the clean room.
Uses of Positive Pressure Dampers
Positive pressure dampers are used in clean rooms. This is because the room must be kept at a positive pressure to prevent dust and dirt from entering from the outside. Air has the property of flowing from higher to lower atmospheric pressure. Dust and dirt in the air also diffuse with the air flow.
Therefore, in clean rooms, the air pressure in the room is increased compared to the air pressure outside the room, thereby creating an air flow from inside to outside the room. This prevents dust and dirt from entering the clean room.
However, if the pressure in the room is too high compared to the outside of the room, adverse effects can occur, such as difficulty in opening and closing doors when entering and leaving the room. In addition, in clean rooms used for semi-conductor manufacturing, the load is so heavy on the workers that they are said to be carrying 2-3 kg on their backs at any one time.
Therefore, by opening and closing the positive pressure damper from time to time in accordance with the pressure difference with the air outside the room, it is possible to keep the air inside a clean room at a constant positive pressure. Depending on the installation method, it may also be possible to make the room negative pressure in the opposite direction.
Principle of Positive Pressure Dampers
A positive pressure damper consists of a damper body, a control unit and an actuator. The control unit sends control signals to the actuator based on information from the pressure sensor. The actuator controls the opening of the damper based on this control signal.
The pressure sensor then detects the difference in air pressure between the inside and outside of the clean room and controls the opening of the valve in the damper body so that the pressure difference is kept to a certain degree. In other words, when the air pressure is higher than the specified value, the damper is opened to discharge air outside the room, and when the air pressure is lower, the damper is closed to keep the air pressure constant.
Types of positive pressure damper?
The main types of positive pressure damper used in clean rooms are:
1. Shutter Dampers.
This type of positive pressure damper controls the passage of airflow by opening and closing. They are generally installed horizontally and adjust the damper opening by opening and closing. Shutter dampers can be opened and closed at high speeds and can therefore cope with sudden changes in air pressure.
2. Damper Unit
These are specialised damper units built into the walls and ceilings of clean rooms. The damper unit has controllable openings to control air supply and exhaust air. Damper units are used in combination with damper boxes and controls.
3. Operating Theatre Dampers.
This system combines several damper units. The system is used to regulate the air pressure in different areas of the cleanroom. Each area can be independently controlled and different cleanliness levels can be maintained.
4. Regulatory Dampers.
In addition to controlling air pressure, these dampers can also control air speed and air volume. This allows the movement of air in the cleanroom to be regulated in more detail. Regulatory dampers are particularly suitable for clean rooms where a high degree of control is required.
5. Dampers With Fire Shutters.
This type of damper automatically closes the opening blades when a thermal fuse blows above a specific temperature. Air flow can be blocked, preventing the spread of fire and the filling of toxic gases.