Process Monitoring and Control

Using SCADA Software Using SCADA Software

The need to automate a process evolves in order to run the process automatically without human intervention, to provide logs, to monitor various parameters of the process and to provide safety interlocks between instruments so as to prevent damage to life and resources, explain N. Sivakumaran, E. V. Kanakasabai and P. S. Raja.

Introduction
Automation of the process industries is increasing day-by-day. The need to automate a process evolves in order to run the process automatically without human intervention, to provide logs, to monitor various parameters of the process and to provide safety interlocks between instru- physiments so as to prevent damage to life and resources. In this project, PLC (Programmable Logic Controller) and SCADA software are used in automation of a simple experimental batch process.
Configuring the PLC Configuring the PLC system involves selecting the model of PLC and setting up the PLC communication serial port. PLC configuration and programming is done through Versapro 2.0.
The PLC module is selected from the catalogue that is available in the software and is configured.
The configuring details are the sweep mode, scan-time and power-supply range.
Similarly, all the I/O modules that are used in the PLC system are selected from the catalogue and configured. The details to be configured are selection of power supply and address for the I/O Modules. All the I/O modules are configured based on the address allocation table.
Programming the PLC A deep knowledge about the process, understanding of electrical schematics and understanding the logic operations - various types of logic and relays - are required in developing the ladder logic. The program is developed based on the interlocks designed. The relays, coils, vertical wire, horizontal wire, timers, counters, mathematical functions, all types of Boolean functions are available in the right pane of the window. Unlike the other software package, the variables are automatically entered into the variable declaration table based on the variables entered while programming. There is no need to enter the variables separately in to the table.

Establishing Communication
between PLC and Programmer To transfer data between PC and PLC, first the communication between them should be established.
A RS-232/RS-485 communication/ programming cable is required to establish the communication physiments cally. Through the software the communication settings such as selection of com port, selection of the baud rate, and selections of the protocol are done.

Storing the Logic and Configuration to the PLC Memory
Prior to storing (after configuring the communication settings), the communication is established through the connect tab present in the toolbar. Initially both the configuration details and the logic are stored. If the storing is successful, the status bar displays “LOGIC EQUAL” otherwise the message will be“LOGIC NOT EQUAL”. The errors encountered while storing will be displayed in the message box of the window.

Experiment Details
Interfacing Hardware Details The process consists of overhead tank (OHT) and process tank (PT). The OHT is placed at a desired height to meet the pressure requirement of the inlet solenoid valve of the PT. The outlet of the OHT is given to the PT through an inlet solenoid valve (%Q0001), there is a supply of 230V to the solenoid valve, which closes when reenergized. The maximum level of the PT is controlled by a float ball valve. When the level of the PT is maximum, the float ball valve moves upward and shuts the inlet to the PT (%I0001). The general layout of the process is shown in Figure 1. The PT contains a 1500 W heater and an agitator (%Q0003), which is rotating at 1380 rpm. Both are energized by a 230V AC supply. When the liquid in the PT reaches level high, there is a supply of 24V to PLC. The heater and agitator are switched on and the inlet solenoid valve of the PT is closed. When the liquid reaches the desired temperature (% I0002),

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