The BRX3 pump operates on differential pressure and is capable of operating against back pressure placed on its exhaust port. Therefore, supply pressure above the differential pressure required to produce the required discharge pressure, can be recovered into a line at a lower pressure than the pump exhaust pressure. Exhaust pressure can be determined using the following chart and the formula:

Exhaust Pressure = Supply Pressure - Differential Pressure

Differential pressure can be estimated using the following chart. For the required discharge pressure (psig) locate the cylinder differential pressure (psig) required for the required plunger size. Note - the differential pressure determined from the chart is the minimum differential pressure and is the point at which the pump will begin to stall. For proper operation a larger differential pressure should be utilized. The larger the differential pressure available, the better the pump will perform, so the pump should be operated using the greatest differential pressure available for optimum performance. Factors which may affect differential pressure requirements include pump plunger friction due to overtightening of the packing and cylinder friction due to dry supply gas or slow operation.

Example: For a discharge pressure of 3000 psig on a 3/8" plunger, model BRX303 pump, the cylinder differential pressure required is 92 psig. Therefore a supply pressure of greater than 92 psig is required for the pump to operate, the pump may stall if the differential pressure reaches 92 psig minimum. For any supply pressure above 92 psig, an exhaust pressure is capable equal to the difference between the supply pressure and the differential pressure required (92 psig). Therefore if a supply pressure of 150 psig is used in the application, there will be (150 psig minus 92 psig) 58 psig maximum available for recovery on the exhaust. For optimum performance the exhaust line should be at a pressure below 58 psig to allow the pump to operate effectively without stalling.