Networks and Communications
FLEX Ex Provides Safe Solution for Hazardous Area
Since Rockwell Automation and system integrator Chemserv started working together five years ago, they have successfully completed a number of projects for DSM Fine Chemicals Austria (DFCA), part of the Dutch chemical group DSM N.V. At the moment the DFCA production site in Linz, Austria has a total of 50 Allen-Bradley controllers, 25 AC drives and 20 soft starters all linked to a plant-wide ControlNet network.
In spring 1999, DFCA presented Rockwell Automation and Chemserv with a new challenge. They were asked to develop the process control system for a filter press.
This was not just a regular application because the project involved a hazardous area. So Rockwell Automation supplied an intrinsically safe solution, providing DFCA with Allen-Bradley ControlNet PLC-5 controllers and Allen-Bradley FLEX Ex I/O, which can be used directly in hazardous environments with a single network connection to external environments.
The filter press is automated by using a high-performance Allen-Bradley PLC 5/80C15, which processes local digital and analogue signals and links an external operating unit to the hazardous area via the Allen-Bradley ControlNet PLC 5/80C15 DF1 protocol. ControlNet, using fibre optic cable, connects the PLC-5 and the FLEX Ex I/O modules in the hazardous area. This technology is used because it allows the user to cover distances of up to 30km and offers high transfer rates of information and reliability. Rockwell Software RSNetWorx software for ControlNet was used to configure the FLEX Ex modules.
By using FLEX Ex, I/O signals can be collected directly in the hazardous area, and via ControlNet, they send information on temperature, pressure, valves and binary contacts back to the control room. FLEX Ex modules are controlled via ControlNet, which is also used to transfer the input and output information needed to control the filter press.
DFCA has very quickly experienced the benefits of using the ControlNet PLC-5 with FLEX Ex I/O combination over ControlNet. As well as having a single network connecting the control room to the hazardous area, the number of terminal blocks, signal barriers and fuses needed is reduced. The system is quicker to install and commission, and overall system costs are significantly lower.
"The main advantages FLEX Ex provide us are reduced panel space, reduced cabling and comfortable extension options. Moreover, we appreciate the modularity, flexibility and the proximity to what happens," said Helmut Danner, project manager, Chemserv.
The control system project was carried out very quickly. After the order was placed only one week was needed to install the system, and the Rockwell Automation Global Technical Services organisation was on hand to provide support for the start-up.