Fluid-flow control system

Claim 1

IN A CENTRIFUGAL COMPRESSOR OR PUMP HAVING AN INLET AND AN OUTLET, A FLUID-FLOW CONTROL SYSTEM COMPRISING (A) A RECIRCULATION-LINE COMMUNICATING AT ONE END WITH THE OUTLET AND AT THE OPPOSITE END WITH THE INLET OF THE PUMP, (B) A RECIRCULATION-VALVE DISPOSED IN SAID RECIRCULATIONLINE AND RESPONSIVE TO A DIFFERENTIAL PRESSURE IN SAID RECIRCULATION-LINE TO CONTROL THE FLOW OF FLUID THERETHROUGH, (C) A PILOT VALVE ASSOCIATED WITH SAID INLET TO BE OPERATIVE IN RESPONSE TO THE MASS FLOW OF FLUID THROUGH SAID INLET, (D) SAID PILOT VALVE CONNECTED TO SAID RECIRCULATIONVALVE TO EFFECT ACTUATION OF THE LATTER TO ALLOW THE FLOW OF FLUID THROUGH SAID RECIRCULATION-LINE WHEN THE PILOT VALVE IS OPERATIVE IN RESPONSE TO A PREDETERMINED MASS FLOW OF FLUID THROUGH SAID INLET, AND (E) AN EQUALIZER LINE COMMUNICATING WITH SAID OUTLET TO RECEIVE FLUID AT A PRESSURE SUBSTANTIALLY THAT OF THE FLUID FLOWING THROUGH SAID OUTLET, (F) SAID EQUALIZER LINE BEING CONNECTED TO CONDUCT SUCH FLUID TO SAID RECIRCULATION-VALVE, WHILE SAID PILOT VALVE IS CLOSED, TO PROVIDE FOR BALANCED PRESSURES ON SAID RECIRCULATION-VALVE AND, UPON OPENING OF SAID PILOT VALVE, TO COMMUNICATE SAID RECIRCULATION-VALVE WITH THE INLET PRESSURE AND CONDUCT THE FLUID FROM SAID RECIRCULATION-VALVE TO UNBALANCE THE PRESSURES THEREON.