Progammable Logic Controller based Design and implementation of automatic pump control in a Filter Press System

07/16/2010 00:00:00

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Waste water treatment process at PT Krakatau Steel utilizes filter press technology, where the waste material is separated into solid substance and harmless liquid form. At present, the filter press system is controlled manually by an operator, resulted in low efficiency and caused several problems due to human error. To overcome this problem, an automatic system is introduced, using pressure transducer as feedback signal, and a Programmable Logic Controller (PLC) as “the brain’ of the system. The system starts working when the screw pump coupled to a three phase induction motor pumps the waste from the collection tank to the filter press through piping system. The pressure transducer continuously monitors the pressure of the waste fluid in pipe, and send this feedback signal to the PLC. Based upon this signal, the PLC will send the appropriate analog signal to the Variable Speed Drives (VSD, also known as Inverter), and the VSD in turn will regulate the motor speed according to the pressure in order to maintain the pressure at permissible value all the time. This control system is implemented using Omron PLC type CPlL with CX Programmer Ver. 7.2 ladder diagram programming language, and two type of VSD: Siemens (for simulation) and Telemecanique (for the real system). Based on simulation, the control system can regulate the motor speed and the pressure is kept within the permissible value.

Keywords: filter press, Programmable Logic Controller, Variable Speed Drives, ladder diagram