Automatic Control of Water Pumping Stations

Automatic Control of Water Pumping StationsMuhannad Alrheeh JIANG Zhengfeng( School of Mechanical-electrical , Wuhan University of Technology ,Wuhan 430070 China )Abstract : Automatic Control of pumps is an interesting proposal to operate water pumping stations among many kinds ofwater pumping stations according to their functions. In this paper , our pumping station is being used for water supply system.This paper is to introduce the idea of pump controller and the important factors that must be considering when we want to designautomatic control system of water pumping stations. Then the automatic control circuit with the function of all components will beintroduced.Key words : water pumping stations ; pumps control ; automatic control1 IntroductionTypically ,a pumping station of a water supply system consists of a set of different pumps. These pumps areused to supply overhead tank ，located through out the community. In time , these tank supply consumers.Pumps work in combination with each other in order to satisfy water demand from the consumers. This systemmust satisfy several hydraulic and technical restrictions. The operation can be performed manually by a start/stop switch for the pump motors ,or by device can control the pumping.The hydraulic model consists of :A water source : the potable water reservoir.An elevated overhead tank , which supplies water on demand to the consumers.A potable water pumping station with pumps used to pump water from a water source to the elevated over-head tank.. A main pipeline used to drive water from a pumping station to an overhead tank.2 Pump ControllerPreviously in case of necessity of water we would simply plug in the extension cord and it would directly runthe pump. And consequently after sometime the water would come out from the pump and would start flowingfrom the pipe.It is a simple example of the idea of pump control systems , and yet all pump controls are no more than avariation on this same procedure. The pumps are started and stopped by switch on or off the power supply. .To get ridof the plug , the next step was to use a permanent switch for turning on or off the power flow .We can use this way for small pumps where , the voltage and amperes are low. A simple switch will not be prac-tical with the higher voltage and amperes commonly used for water pumping station.The switch would have to be vast to handle the load. Also there are the safety problems , if you increase thevoltage to 240 volts and 15 amps !( By the way ,it' s the amps that kill you , not the voltage !). To avoid thisproblem and isolates the user from the pump voltage , most pump control circuits are designed using a relay cir-cuit. The relay circuit is intermediate between user and pump. Most relays use 12 or 24 volts ,a few use 120volts.The decision of the type of control system for water pumping station and water supply system should beproviding maximum stable system with economic design and it must provide protection against simultaneousstarting of all pumping units following a power interruption. Some control systems work with manual start andautomatic stop will be the most economical. The disadvantages of automatic controls are increase complexity dueto the additional control equipment and greater cost. But ,som中国煤化工e use of automatic startand stop controls to be an advantage. Automatic controls are m{Y片C N M H Gtion due to long periodsof disuse and will require more frequent inspection and maintenance to keep them In working order. W orkforcewith the knowledge and skill required for maintenance of automatic control equipment should always be avail-able. Automatic controls must be compared with the justified alternative manual controls. Automatic controlsmust have a manual control backup.一147-3 Optimum Control of Multi-factors* Water level in the overhead tank ;Pumps should start pumping immediately when the water level in the tank falls below a certain low level( L). Subsequently , as the water level in the tank rises to an upper level( M ) , the pump switched off automati-cally. The pump is turned on again only when the water level again falls below level L in the tank , provided thelevel in the source is above R in Fig. 1. This automated action continuesHOverhead tankW ater consumersMain pipe lineM11243|(M4)PumpsWater sourceFig.1 Water supply system￥Water level in the source ;It should ensure that there is water in the source before starting the pumps. Because if no water in thesource and the pumps are working then the pumps will be broken.* Water demand from the community ;We can see in Fig.2. The volume of water demand is not the same during the whole day. The maximumwater consumer is between 9-11 AM and the minimum is between 2-4 AM6.32.845.845.475.05.034.283.91" 3.102.73_2.31.921.55123456789101112131415161718192021222324Time/hourFig.2 Water demand curve￥Electric energy costIt is the cost of electric energy consumed by all pumps. In addition , there is an important factor. Where ,the electric energy cost is not the same during the whole day. Minimum cost( cmin ):from 0.00 to 17.00 hoursand from 22.00 to 24.00 hours.Maximum cost( cmax ): from 17.00 to 22.00 hours.￥Hydraulic and technical restrictions ;The control system must satisfy some hydraulic and techn中国煤化工( 1 )Pump motors must stop if the pump is not delivering( 2 )Pump motors should not operate continuously more thMYHCN M H Git should stop afer theset running time is over.( 3 )Prevent occurrence of water hammer. ( Water hammer , as it is known is the result of a sudden changein liquid velocity. W ater hammer usually occurs when a transfer system is quickly started stopped or is forced to_ 148方数据make a rapid change in direction. )( 4 )Protect the pumps from cavitation. ( It is occur when the local static pressure of water before the pumpreach a level below the vapor pressure at the actual temperature. )( 5 )The pumps can be controlled manually at any time by using the start/ stop( manual ) button4 Control SystemThere are many kinds of control systems of water pumping station according to the aim of this station. Irthis paper，our pumping station is using for water supply system. The schematic diagram of automatic controlwater supply system can be designed as in Fig.3. and Fig. 4. This system is for automatic operating four pumpsand control water supply system buy using programming logic controller. Where :S2SRPLCFig.3 Schematic diagram of automatic control water supply systemR : is the references input like the minimumSIvalue of pressure in the sump ( before the pump ).This value of pressure is very important to preventOverhead tankthe cavitation.SlQ :it is the output( water flow )S1 :it is a sensor to sense the water level in theoverhead tank ;it will send a signal to summing pointwhen the water level in the tank falls below a certain、s4、Pumpslow level( L) ,as the water level in the tank rises to年了2s3an upper level( H )，the pump switched off automat-ically. Then we can control the water level in theoverhead tank by close loop control.PowerWater sourceS2 :it is a sensor that senses there is water in2the source or the sump of pump. S3 :this sensor is toFig.4 Automatic water pumping station controlmeasure the pressure before the pump，where thevalue of this pressure is very important to prevent cavitation. It must be more the vapor pressure at the actualtemperature.S4 : this sensor is to measure the motor pump temperature. It is more safety for the motor pump.M : the motor pumpThe summing point :is using to compare between the references value and the measured value and then sendthe error signal.5 ConclusionsAutomatic control is a highly effective method to control , safe and operates water pumping stations. Whereit is provided with the following various conditions to start pumping : Low water in overhead tank , presence ofwater in the sump of pumps , and all pumps are ok. Also it has the flexibility to modify the control sequence orto add new pumps in future.中国煤化工MHCNMHG一149-