Plant Maintenance
connecting dissimilar upper-level networks. More importantly, it opens the door to system-wide communication while offering better tools to control motors and increase plant efficiency. When properly deployed, the intelligent MCC allows users
to monitor and analyse operations from anywhere at any time. With access to more detailed information over longer periods of time, users can better predict potential problems and prevent catastrophic failures. For maximum network efficiency, engineers can configure devices to report data as often and in whatever format as needed. For example, a drive controlling a rapidly fluctuating process might report status every 50 milliseconds, while a motor on a slower changing process may only be required to report status every 60 seconds. For most parameters, devices can be configured to communicate only on a change of state. Diagnostic data can be accessed outside of the regular data scan, keeping all data available without clogging the network with information that’s only used occasionally. Information reported by devices in the system can be recorded for later analysis, if needed, or used to generate alarm messages as important events occur in the process. Up until now, MCCs lacked interwiring and required
extensive field wiring, documenting, testing and system integration. Conversely, the intelligent MCC arrives preconfigured, pretested and ready to install. The communication cables are installed and tested, intelligent devices are preprogrammed and software screens are pre-configured, all of which help reduce start-up time. The primary drawback of many network configurations, such as those in a daisy-chain configuration, is the inability to
make device changes or additions without shutting down the network. With this type of topology, moving or adding devices requires the technician to break the chain, thus disabling the network. A better approach is to isolate trunk and drop lines behind barriers, avoiding potential damage to communication cables during installation and maintenance activities. Trunk and drop network design provides easy-connection communication ports that allow devices to be plugged or unplugged without network disruption. This configuration should also provide independent, readily accessible ports to simplify installing, withdrawing, relocating and adding plug-in units. Engineers require detailed documentation for fast start-up
and efficient troubleshooting, but this documentation is often misplaced or incomplete With an intelligent MCC, users can access electronic documentation on the same PC running the monitoring software.
A prime opportunity As the cost of intelligent devices continues to decline, intelligent MCCs offer manufacturers an excellent opportunity to benefit from advanced technology of these control systems, including improved diagnostics, increased system reliability, design flexibility and simplified wiring. While a robust, reliable design is critical for helping to contain faults and minimis downtime, equally important is the device-level networking capabilities of today’s intelligent MCCs. ❒
For a copy of the white paper, visit
http://samplecode.rockwellautomation. com/idc/groups/literature/documents/wp/mcc-wp001_-en-p.pdf
Fig. 1. Intelligent MCCs present chemical manufacturers with a major opportunity to capture and use equipment and process data in order to improve productivity and maximise asset availability.
Image courtesy of BASF.
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