| 摘要 |
1489361 Centrifugal pumps P HAYWARD 16 Oct 1974 [17 Oct 1973] 44921/74 Heading F1C In a pipe-line which includes at least two sections each having a characteristic maximum internal pressure to which it may be subjected without experiencing an unacceptable probability of mechanical failure each section being headed by a pumping station having at least one variable pitch bladed rotary pump for increasing the pressure of the fluid forwarded to that station, the section subjected to an internal pressure nearest to the characteristic maximum for that section is continuously detected, and the blade pitch of the pump of the station heading that section is maintained so as to tend to sustain that nearest internal pressure, and the blade pitch of the pump at the station heading the at least one other section is varied to accommodate the rate of flow through the first-mentioned section. An initial pumping station 8, Fig. 3, and intermediate pumping stations 8, 10, 11 spaced along a pipe-line each comprise at least one pump 24 with variable-pitch rotor blades as described in Specification 1343986 or with variable-pitch stator blades (two pumps 24 being provided in station 11) in series with a standard centrifugal pump 22, the intake pressure, flow-rate and discharge pressure in each station being sensed by respective sensors 18, 19, 20, the sensors each providing an electrical input to a central control unit 21 which provides an electrical output to a servomotor 17 associated with each pump 24 for adjusting the blade pitch. Sensors for density and viscosity of the liquid may also be provided. Generally, the regulation is such as to provide either a desired flow or a desired pressure at the downstream end of the final section 15 of the pipe-line, subject to the over-riding condition that the maximum allowable pressure in each section is not exceeded. Instead of a central control unit 21, a separate local control unit for each pumping station may be provided, the inputs and outputs of each local control unit being connected to its own pumping station only. When two pumps 24 are provided in a pumping station, either in series as in station 11 or in parallel, the control may be such as to put either one or both pumps into operation according to the requirements of flow and pressure and taking into account also the achievement of maximum efficiency. For this purpose, the control unit may include two three-dimensional cam arrangements which provide respective outputs indicative of the efficiency of a single pump and of the combination of the two pumps respectively when operating at the prevailing combination of flow-rate and pressure and controlling the starting and stopping of the pumps accordingly. An analog or digital computer may be used instead. Fig. 6 shows a starting arrangement for a pumping station located at the junction between sections 113 and 114 of a pipeline and comprising a single pump 124 and a single pump 122 corresponding to the pump 24 and the pump 22 respectively. Initially, valves 129', 131 and 133 are closed and pump 124 is started with a blade angle close to zero. When pump 124 has reached its normal speed, the valve 133 is opened and the blade angle is gradually increased to bring the pump pressure up to a high value, and then the fixed-vane pump 122 is started. Thereafter, valve 131 is opened and valve 129 is closed while the blade angle of pump 124 is rapidly reduced to zero, whereby the combined pressure of the two pumps in series remains constant. Thereafter, the blade angle may be increased again if the pump 124 is to contribute to the total pressure. |
