PLC-based system expansion in petrochemical plant

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October 2002 PLCs, DCSs & Controllers

A petrochemical company was expanding quickly owing to the strong economy. Economic growth was so rapid that the company frequently experienced shortages of raw materials, with demand for its products often outpacing supply.

Maintaining economies of scale is a crucial factor for petrochemical companies to retain their competitiveness. Losing even a small market share to competitors can be disastrous for such companies. Thus, the factory manager proposed to the board of directors that certain production lines be expanded to keep the company competitive. This plan included the installation of a data monitoring and control system in those production lines.

One of the key constraints facing system integrators is time. The factory manager promised the executive board that the new installation would be completed within a short period of time. That meant the monitoring system had to be easy to install. The production facility buildings are large and high, so the wiring system had to be flexible and easy to maintain. Data collected on site had to be reliable and not affected by EMI during transfer. Also, due to forecasted strong demand over the next few years, the factory manager was very concerned about the scalability and future expansion of the system.

The first option for the system integrator was to merely expand the existing PLC system. After further assessment, this proved to be too complex. He then decided to implement an open PC environment. Advantech's ADAM series of PC-based data acquisition modules were selected.

The configuration is set up on the original PLC system's communication module. The PLC reads data from the ADAM modules and sends it to the control room through an RS485 network. The RS485 network, with its simple, twisted pair construction, is suited to applications calling for ease of installation.

The ADAM-4013 is used to read temperature, the ADAM-4017 for collecting transmitter signals, while the ADAM-4050 reads and controls relays, fans and pumps. A fire alarm function watches for abnormal conditions in the continuously running production line. As a result, realtime emergency action can be swiftly carried out.

Due to the choice of open PC-based architecture, the expansion plan was finished on time. ADAM's PC-based design proved to be fully compatible with the PLC system. The system engineers, maintenance staff and field workers were all delighted with the results. Most importantly, the company's throughput now fully satisfies customers' demands.

For more information contact Elton Prytz, ProMicro, 011 706 7913, [email protected], www.promicro.co.za

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PLC-based system expansion in petrochemical plant

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