Water Distribution Network

Abstract

In a water distribution network having at least one pump for distributing water over the network, the pump is driven by an electric motor and a variable speed device, and there is a device for operating the pump in phases. On starting the pump in a first starting phase the pump speed rises rapidly from zero to a threshold speed between zero and a maximum pump speed, in a second starting phase the threshold speed is maintained, in a third starting phase the pump speed is increased more slowly to a maximum speed, and in a fourth operating phase the maximum speed is maintained. On stopping the pump, in a first stopping phase the pump speed decreases gradually from a maximum speed to an intermediate speed, and in a second stopping phase the pump speed decreases rapidly from the intermediate speed to zero.

What is claimed is: 
     
         1 . A water distribution network having at least one pump device for distributing water over the network, the pump device comprising a pump driven by an electric motor and a variable speed device, and a device for operating the pump in phases, such that on starting the pump in a first starting phase the pump speed rises rapidly from zero to a threshold speed between zero and a maximum pump speed, in a second starting phase the threshold speed is maintained, in a third starting phase the pump speed is increased more slowly to a maximum speed, and in a fourth operating phase the maximum speed is maintained. 
     
     
         2 . The water distribution network as claimed in  claim 1 , wherein the increase of pump speed in the third starting phase includes stages of increase and maintained speed until the maximum speed is reached. 
     
     
         3 . A water distribution network having at least one pump device for distributing water over the network, the pump device comprising a pump driven by an electric motor and a variable speed device, and a device for operating the pump in phases such that on stopping the pump, in a first stopping phase the pump speed decreases gradually from a maximum speed to an intermediate speed, and in a second stopping phase the pump speed decreases rapidly from the intermediate speed to zero. 
     
     
         4 . The water distribution network as claimed in  claim 3 , wherein at least one further phase is included, such that the intermediate speed is maintained in a third stopping phase, before the second stopping phase of rapid decrease to zero. 
     
     
         5 . The water distribution network as claimed in  claim 4 , wherein the third stopping phase includes stages of maintained speed and decrease. 
     
     
         6 . A water distribution network having at least one pump device for distributing water over the network, the pump device comprising a pump driven by an electric motor and a variable speed device, and a device for operating the pump in phases, such that on starting the pump in a first starting phase the pump speed rises rapidly from zero to a threshold speed between zero and a maximum pump speed, in a second starting phase the threshold speed is maintained, in a third starting phase the pump speed is increased more slowly to a maximum speed, and in a fourth operating phase the maximum speed is maintained, and such that on stopping the pump, in a first stopping phase the pump speed decreases gradually from a maximum speed to an intermediate speed, and in a second stopping phase the pump speed decreases rapidly from the intermediate speed to zero, wherein the intermediate speed is the same as the threshold speed. 
     
     
         7 . The water distribution network as claimed in  claim 1 , wherein the pump operating means comprises a microprocessor device, such as a programmable logic circuit, used to control the variable speed device to control the electric motor. 
     
     
         8 . The water distribution network as claimed in  claim 7 , wherein the programmable logic circuit is separate from the pump or provided as a component of the pump. 
     
     
         9 . The water distribution network as claimed in  claim 3 , wherein the pump operating means comprises a microprocessor device, such as a programmable logic circuit, used to control the variable speed device to control the electric motor. 
     
     
         10 . The water distribution network as claimed in  claim 9 , wherein the programmable logic circuit is separate from the pump or provided as a component of the pump. 
     
     
         11 . The water distribution network as claimed in  claim 1 , wherein the variable speed device includes an inverter used to control the frequency and voltage supplied to the electric motor according to the demand in the system. 
     
     
         12 . The water distribution network as claimed in  claim 11 , wherein the inverter is connected to a non-return valve for the pump. 
     
     
         13 . The water distribution network as claimed in  claim 12 , wherein the points at which the non-return valve opens and closes are used to determine the transitions between the starting or stopping phases. 
     
     
         14 . The water distribution network as claimed in  claim 13 , wherein on pump starting, the open point of the non-return valve determines the end of the first starting phase. 
     
     
         15 . The water distribution network as claimed in  claim 13 , wherein on pump stopping, the close position of the non-return valve determines a change in the rate of decrease at the intermediate speed. 
     
     
         16 . The water distribution network as claimed in  claim 12 , wherein a pressure sensor is provided on each side of the non-return valve. 
     
     
         17 . The water distribution network as claimed in  claim 16 , wherein the pressure sensors are connected to the pump operating means to indicate when the non-return valve is about to open. 
     
     
         18 . The water distribution network as claimed in  claim 17 , wherein the pump operating means determines the pump speed at the open position automatically. 
     
     
         19 . The water distribution network as claimed in  claim 3 , wherein the variable speed device includes an inverter used to control the frequency and voltage supplied to the electric motor according to the demand in the system. 
     
     
         20 . The water distribution network as claimed in  claim 19 , wherein the inverter is connected to a non-return valve for the pump. 
     
     
         21 . The water distribution network as claimed in  claim 20 , wherein the points at which the non-return valve opens and closes are used to determine the transitions between the starting or stopping phases. 
     
     
         22 . The water distribution network as claimed in  claim 21 , wherein on pump starting, the open point of the non-return valve determines the end of the first starting phase. 
     
     
         23 . The water distribution network as claimed in  claim 21 , wherein on pump stopping, the close position of the non-return valve determines a change in the rate of decrease at the intermediate speed. 
     
     
         24 . The water distribution network as claimed in  claim 20 , wherein a pressure sensor is provided on each side of the non-return valve. 
     
     
         25 . The water distribution network as claimed in  claim 24 , wherein the pressure sensors are connected to the pump operating means to indicate when the non-return valve is about to open. 
     
     
         26 . The water distribution network as claimed in  claim 25 , wherein the pump operating means determines the pump speed at the open position automatically.