Dry ring ventilation device
A dry ring venting device is connected upstream of a (non-self-priming) centrifugal pump in order to vent the inlet to the pump. It is used in fire extinguishing pumps .
The dry ring pump works on the principle of the connecting rod piston pump. She sucks and pushes at the same time. An eccentrically mounted connecting rod piston mounted on a drive shaft rotates in the housing of the dry ring pump . This connecting rod piston creates a crescent-shaped cavity on its outside and a second crescent-shaped cavity on its inside, which enlarge behind the piston with one revolution and thus create a negative pressure, but at the same time reduce the space in front of the piston and increase the pressure there. The atmospheric air pressure pushes air through the inlet opening into the cavities. The rotary movement makes these cavities smaller and presses the air out through the outlet opening or from the inside onto the outside of the connecting rod piston. At the same time, it creates a negative pressure on the other side of the rotary piston, into which air can flow again.
The difference to the liquid ring bleeding device is that the dry ring bleeding device has to be filled with standard engine oil for sealing and the liquid ring bleeding device with water. This oil would then be released into the environment with the extinguishing water. That is why this system was discontinued.