Bleed valves are used on screw compressors or rotary vane compressors: As a component of the zero load bypass system, when the compressor is controlled by an inverse acting proportional controller and the discharge pressure has to be kept constant.To blow off air in course of either start-up or shut-down procedures.
LSVV applied as a component of the zero load bypass system:
The bleed valve LSVV is governed by the pneumatic signal of the invers acting proportional controller. It opens steplessly and blows off excess air if the controller signal decreases to zero load level. Thus the minimum suction pressure and the desired pressure ratio for zero load conditions is maintained accurately. The approximate loga-rithmic flow characte- ristic of the LSVV ensures smooth transition from load to zero load condi-tions by gradually increasing blow off air quantity.
The inlet P is connected to the main line down-stream
from the minimum pressure valve MPVL. The lateral outlet connection R can be either connected to a venting air line leading to the inlet of the suction control valve (closed bypass system) or equipped with a suitably sized silencer for full blow off capacity.The signal pressure inlet E on top of the LSVV is connected to the signal pressure line down-stream from the proportional controller LPN.