Using PLC and frequency converter for optimizing reconstruction - 1250 electric control system of centrifuge

1。 Preface

1250 centrifuge is vertical scraper discharge automatic filtering centrifuge, is mainly used for solid phase for granular solid liquid separation of suspended material, also can be used for solid liquid separation of fibrous material. In the mineral, environmental protection, widely used in pharmaceutical, chemical and other industries. At present most of the centrifuge are still controlled by relay, adopts step speed regulation, centrifuge speed setting of the single, equipment failure rate is higher, the production efficiency is low. In order to overcome these problems, we are pharmaceutical factory 1250 technical renovation, electric control system of centrifuge adopts PLC and frequency converter speed control, the system is a high degree of automation, good stability, reliable operation, has been successfully applied in several pharmaceutical companies.

2。 System principle

centrifuge working principle is to pass through the feeding tube for the separation of material into the high-speed centrifuge drum, under the action of centrifuge force field, the material through the filter cloth ( Mesh) Realize filtering, liquid through a liquid discharge tube, solid phase intercept in the drum, to stay inside the drum filter cake meet the minimum charge, the machine stop charging, the filter cake washing, washing liquid filter out at the same time, meet the requirements of separation, centrifuge speed, scraper device, blowing the filter cake, to complete a working cycle. Figure 1 is 1250 centrifuges structure.

the centrifuge process: 1) Feed: when the inverter speed reaches 20 hz, first open the feed valve, check valve, when the detected material layer is full, close the feed valve and time delay 10 s, material layer with signals disappear again open the feed valve for executing the above action 2 times. 2) Centrifugal: when the third material full signal, inlet valve inverter up to 50 hz close to high-speed separation, centrifugal time set by the touch screen, frequency converter speed down to 40 hz after their time. 3) Clean dry: open the purge valve cleaning, cleaning time, pause time and washing time according to the separation of drug varieties set by touch screen. After the completion of the cleaning process in the process of dry, inverter frequency 50 hz, dry time set by touch screen. Time to enter into the state of discharge. 4) Discharge: due to the too thickness of material layer after dry, scraper with subsection timing rotation discharge, namely blade rotation ( Time can be set) To stay up to 2 seconds, scraper ( Drop height can be set) , repeat the above action, until finally a scraper descend to lower limit sensor movement, and then rise to the top is the highest limit stop. Hardware design 1

system USES mitsubishi FX2N - Mr Programmable controller (40 PLC） Control, when the program is set to select the nobody care automation or manual control, and the early feeding, filtering, washing, filtering, discharge of the whole process of monitoring. Centrifuge speed PLC + D/A module, frequency converter speed control, through the voltage ( 0 - 10 v) To control the frequency of the inverter, inverter adopts Germany lenz company EVF series inverter, 22 kw power. Touch screen with EASYVIEW 5. 7 inches four gray touch screen.

input PLC with 20 points, 15 dots. Figure 2 for PLC external hardware configuration diagram. The main loop of the control system and inverter external connection as shown in figure 3. 2 software design

by using programming software, programming MELSECMEDOC professional software package, which is based on personal computer, is suitable for mitsubishi PLC controller user program compiled and monitoring, through the SC - 09 rs232 / RS422 interface with PLC controller programming port is linked together, can use ladder diagram or instruction programming. This system according to the control of PLC ladder diagram program, require the use of the STL and SET step by step instructions. Mainly include initialization setting, feeding, separating, cleaning, dry control procedures, automatic control, etc. Programming take safety protection are: speed detection, vibration protection, open cover protection, motor overload overheat protection, scraper rotating, lifting machinery electrical dual control, scraper and the linkage of the drum locking. Program flow chart 4 shows, due to long process, need to ask for the program please contact the author of this reference.

4。 Conclusion

the system after several field operation, the result is satisfactory the indicators meet the technical requirements. System startup is smooth, adjustable separation factor, operation simple and convenient, since the reform in operation, stable running convenient speed adjustment, free maintenance, for site operation personnel created an efficient working environment, to achieve the 1250 centrifuge is relatively advanced control technology.

editor: gt

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