When the area at a low terrain, the number of sprinklers and less, H net reduction, the pump head is higher than the nozzle rated working pressure. At the same time the number of nozzle less, the need to reduce the flow area, the system pressure will be high, but also make the nozzle pressure is greater than the rated pressure, so that the nozzle flow is much larger than the rated flow, the pump operating point lower than normal, that Q ~ G The curve is at the lowest point where Q "~ G" and Q ~ H intersect at point A. The terrain elevations are the same as those in the normal working point, but when the number of nozzles is small, the system pressure will be high due to the decrease of flow in the area, Pressure and flow are greater than the rated value, the pump operating point higher than the normal point. Q ~ G curve up to Q "~ G", and Q ~ H intersection at the point A. Obviously the above conditions, the nozzle are Non-rated work, affecting the use of results, serious damage to the nozzle. So you must take measures to make the nozzle work within the allowable pressure range, the project commonly used in the following ways. (1) off small work area inlet valve Or close the small water pump outlet gate valve, a considerable increase in the pipe resistance coefficient, so that Q ~ G curve rise, and the pump Q ~ H intersects the flow point required for the area, the excess head wasted on the valve. (2) With several different head and different flow pump combination, according to the different sections of the head, flow pump or pump operation options, this valve pressure loss without the way, but in complex terrain, the nozzle is very uneven distribution of the project will be (3) pump speed: pump speed, the basic efficiency of the same, so you can reduce the speed, so that the intersection of its characteristic curve and the system characteristic curve flow in B ', B "and B? point. At this time its corresponding speed is to meet the needs of traffic, without any head waste, and its work efficiency is higher. Although the pump speed control measures, but its investment is large, but not in any case are economically reasonable, in order to prevent blindness in the work should be carried out before the application of energy-saving calculations and economic comparison. 3, the choice of speed control equipment (1) speed pump characteristics should be selected so that the speed control pump in the design portfolio to meet the maximum design of water on the basis of speed control as much as possible the characteristic curve, close to the system characteristics curve. (2) speed control equipment selection: speed control equipment, many different types of performance are also different in the sprinkler pumping station speed control should use variable frequency or electromagnetic slip clutch. Frequency control technology is relatively new, higher efficiency, better maintenance conditions, but requires a higher management technology, investment is larger. Electromagnetic slip clutch control part of the simple, low price, easy maintenance, but the transmission efficiency at low speed is low, suitable for high speed and high rate of change or financial constraints, the management of low technology conditions. (3) Pressure regulation during operation of pump room: After starting the pump, the zones are respectively enabled to adjust the pump speed so that the water pressure in the pump room is suitable for the nozzle work. The pressure is the corresponding control pressure in each area. As long as the operation of the area according to the opening, pump room water pressure to the corresponding control pressure can be.