Method for controlling a pump arrangement, and pump arrangement

Abstract

A method for controlling a pump arrangement comprising a fluid delivering pump having a pump drive, a bypass line having a bypass valve for routing fluid back from an outlet side of the pump to a reservoir is disclosed. During ramping up the pump drive to a predetermined target rotational speed, the bypass valve is controlled to reduce a volume flow through the pump so that the volume flow, at a respective delivery height, lies between a cavitational volume flow and the cavitational volume flow increased by a predetermined maximum volume flow deviation.

1 . A method for controlling a pump arrangement comprising:
 providing a pump arrangement including at least one pump having a pump drive, and a bypass line having a bypass valve for routing fluid back to a reservoir from an outlet side of the pump;   ramping up the pump drive to a predetermined target rotational speed; and   controlling the bypass valve for reducing a volume flow through the at least one pump so that the volume flow, at a respective delivery height, lies between a cavitational volume flow and the cavitational volume flow increased by a predetermined maximum deviation of the volume flow.   
   
   
       2 . The method according to  claim 1 , wherein controlling the bypass valve comprises: controlling the bypass valve in such a way that the volume flow at a corresponding delivery height is situated in a volume flow range which lies between a lower limit volume flow and the cavitational volume flow increased by the predetermined maximum deviation of the volume flow. 
   
   
       3 . The method according to  claim 1 , comprising:
 providing a pump with an open bypass valve;   specifying a target rotational speed for a pump drive as a function of a predetermined outlet pressure;   reducing the flow rate through the bypass valve for increasing the delivery height of the pump and reducing the volume flow with a predetermined maximum change of the rotational speed of the pump drive during a first power-up phase;   controlling the bypass valve for increasing the rotational speed of the pump drive so that with increasing delivery height, the volume flow is higher than the cavitational volume flow, which corresponds to a minimum volume flow necessary to avoid cavitation at a respective delivery height, during a second power-up phase; and   closing the bypass valve once a predetermined delivery height or a predetermined outlet pressure has been reached during a third power-up phase.   
   
   
       4 . The method according to  claim 3 , comprising:
 operating an operating point of the pump in the first power-up phase essentially along a delivery height-volume flow curve of the pump at a constant rotational speed.   
   
   
       5 . The method according to  claim 3 , comprising:
 operating an operating point of the pump in the second power-up phase essentially in parallel to a cavitation boundary of a set of delivery height-volume flow curves of the pump.   
   
   
       6 . The method according to  claim 3 , comprising:
 determining a current volume flow as a function of a pressure difference between an inlet side and an outlet side of the pump and the current rotational speed of the pump drive.   
   
   
       7 . The method according to  claim 1 , comprising:
 operating an asynchronous motor as pump drive with a three-phase frequency corresponding to the predetermined target rotational speed.   
   
   
       8 . A pump arrangement comprising:
 at least one pump having a pump drive;   a reservoir providing fluid to be delivered on an inlet side of the at least one pump;   a bypass line having a bypass valve for routing fluid from an outlet side of the at least one pump to the reservoir; and   a control device adapted to ramp up the pump drive of the at least one pump to a predetermined target rotational speed, and to control the bypass valve for reducing a volume flow through the pump so that the volume flow, at a respective delivery height, lies between a cavitational volume flow and the cavitational volume flow increased by a predetermined maximum deviation of the volume flow.   
   
   
       9 . The pump arrangement according to  claim 8 , wherein the control device is adapted to specify a target rotational speed for a pump drive as a function of a predetermined outlet pressure. 
   
   
       10 . The pump arrangement according to  claim 8 , wherein the control device is adapted to reduce the flow rate through the bypass valve for increasing the delivery height of the pump and for reducing the volume flow with a predetermined maximum change of the rotational speed of the pump drive during a first power-up phase. 
   
   
       11 . The pump arrangement according to  claim 10 , wherein the control device is adapted to control the bypass valve for increasing the rotational speed of the pump drive so that with increasing delivery height, the volume flow is higher than the cavitational volume flow, which corresponds to a minimum volume flow necessary to avoid cavitation at a respective delivery height, during a second power-up phase. 
   
   
       12 . The pump arrangement according to  claim 11 , wherein the control device is adapted to close the bypass valve once a predetermined delivery height or a predetermined outlet pressure has been reached during a third power-up phase. 
   
   
       13 . The pump arrangement according to  claim 8 , comprising a cavitation limit control device adapted to control the bypass valve as a function of a current volume flow through the pump and a current rotational speed of a pump drive of the pump. 
   
   
       14 . The pump arrangement according to  claim 13 , comprising a pressure control device adapted to detect the outlet pressure and to control the bypass valve so that a predetermined maximum outlet pressure is not exceeded, wherein the cavitation limit control device is prioritized over the pressure control device. 
   
   
       15 . An air separation plant comprising at least one pump arrangement including:
 at least one cryogenic pump having a pump drive;   a reservoir providing fluid to be delivered on an inlet side of the at least one cryogenic pump;   a bypass line having a bypass valve for routing fluid from an outlet side of the at least one cryogenic pump to the reservoir; and   a control device adapted to ramp up the pump drive of the at least one cryogenic pump to a predetermined target rotational speed as a function of operating specifications for an air separation process, and to control the bypass valve for reducing a volume flow through the at least one cryogenic pump so that the volume flow, at a respective delivery height, lies between a cavitational volume flow and the cavitational volume flow increased by a predetermined maximum deviation of the volume flow.