A valve that is normally used to vent a pressurized tank. The valve can also be used to recirculate gas from a high pressure to low pressure system. The valve can have an orifice on the exit so that the flow is controlled. The valve is fully pneumatic so that no spring is present. The valve is piloted to act, and the system operates to return the valve.
The normally closed blow down valve is commonly used to blow down the air/oil separator tank of a rotary screw compressor. The valve is attached to the tank, so the tank pressure keeps the valve closed. To “blow down” the tank the valve is piloted open. The piston is designed so that the pilot pressure is less than the tank pressure. The Blow Down valve is a piloted normally open or normally closed valve.
It evacuates the compressed air in the air-oil separation tank each time the compressor runs on a no-load and when the compressor shuts down to ensure there is no back pressure when the compressor starts to load next time.
The effective performance of the blow down valve affects the compressor’s power consumption during un-load, capacity of the compressor when running on load, and the life of the motor.
If the blow down valve does not fully and quickly open to evacuate the sump pressure, then the power drawn during unload remains much higher than what it ideally should be.
The valve is normally used to vent a pressurized tank. The valve can also be used to recirculate gas from a high pressure to low pressure system. The valve can have an orifice on the exit so that the flow is controlled. The valve is fully pneumatic so that no spring is present. The valve is piloted to act and the system operates to return the valve. The normally closed blow down valve is commonly used to blow down the air/oil separator tank of a rotary screw compressor. The valve is attached to the tank so the tank pressure keeps the valve closed. To “blow down” the tank the valve is piloted open. The piston is designed so that the pilot pressure is less than the tank pressure. The Blow Down valve is a piloted normally open or normally closed valve.
If the blow down / unloader doesn’t open anymore, compressor will experience startup problems. the typical blow-down of compressed air when the compressor stops will not be heard.
If the blow down / unloader stays open, a continues leak noise of compressed air will be heard.
In case of lubricated screw compressors, if the blow down valve does not quickly open upon receiving ‘unload’ signal, then the sump pressure does not drop quickly resulting in high energy consumption during unloaded condition.
