The Bypass Design In The Variable Frequency Constant Pressure Water-supplying System

Nowadays, the constant pressure water-supplying system based on variablefrequency speed control theory is widely used in the water-supplying plants ofthe petrochemical industry, in order to keep an instrument supplying water stably.However, the pressure of pipe nets in the constant pressure water-supplyingsystem is likely to fluctuate because of many reasons, such as the voltagefluctuation of the outer power system, the fault in the power distribution system,the trouble of the water-supplying motors, and so on. The traditional method todeal with the fluctuation is mostly dependent on operators' quick and calmresponse, and their resolute ability to deal with urgent cases on the scene. Oncethe case is dealt with improperly, there will be shutdown of the key devices inthe departments of thermoelectricity, oil refinery, chemical industry, polyester,and so on, which may cause such a severe accident as a paralysis of thepetrochemical system.To deal with this case, based on producing practice, this article designs abypass system to improve the operating status of the constant pressurewater-supplying system that works in the way of variable frequency andconstant speed. It consists of the computerized comprehensive protectiondevices of the motors, the computerized non-electronic-signal-collecting devices,the intelligent pressure transducer, the industry-controlling computer, and otherrelative hardware devices. The system can perform a real-time monitor on thewater-supplying system with the pressure information, which is collected by theintelligent transducer and transmitted to the industry-controlling computer bythe analog-value-collecting device, and the high-pressure-switch information,which is collected by the comprehensive protection devices. When there appearsa pressure fluctuation, the industry-controlling computer can start the mostproper reserve motor, to reduce the fluctuating time of the pressure of the systemto a minimal size. Compared with the traditional methods, the bypass system hasthe merits of speed, reliability, selectivity and so on. Therefore, it is an idealmethod to keep the constant pressure water-supplying system working stably.This paper introduces the basic knowledge on variable frequency speedcontrol and bypass system, including the basic principle of variable frequencyspeed control, the principle and the structure of the unit bypass and industrialfrequency bypass. It designs the hardware system that can perform a real-timemonitor on the pressure of the pipe nets and the switch information. Accordingto the function the bypass system has to perform, it draws the flowing charts ofthe main program and the son programs for the start of the reserve motors.Based on the flowing charts, a C-language program is designed and practices thebypass function on the industry-controlling computer when the pressure of thepipe nets fluctuates.