THE WANNER MODEL A52 PRESSURE CONTROL AND HYDRAULIC UNLOADER VALVE IS FOR USE IN HIGH PRESSURE PUMPING INSTALLATIONS WITH INTERMITTENT LOADING.  THE A52 ACTS AS A PRESSURE REGULATOR BY MODULATING FLUID FLOW THROUGH A BYPASS VALVE.  WHEN THE DISCHARGE LINE FROM THE CONTROL VALVE IS CLOSED, THE FLOW IS DIVERTED PAST THE BYPASS VALVE TO REMOVE THE PRESSURE LOAD FROM THE PUMP.