Programmable Logic Controller

Only when a plant is on automatic mode and the operator no longer uses manual bypass does a Programmable Logic Controller prove its worth. The first step in the process of working with a PLC-based system is to develop the process sequence from reading, rather than hardware selection criteria. Based upon the number of I/O points, communications' required and future extensions, you select the controller platform. A compact TM200 or TM221 would most likely support the small utility systems without issues. Larger automation lines would require a modular system such as the M340 or M580 because they can accommodate more data transfer, remote I/O connectivity, and SCADA connectivity, yet still maintain acceptable scan times.

The PLC Control panel layout will follow signal discipline within the Control panel. The Power wiring will always remain separate from the Analog and Communications' loop wiring. Shield Grounds will be engineered to be connected at one point to eliminate noise from the feedback signals. Field terminals will be laid out based on the actual direction of cable entry so that commissioning teams do not require additional hours cross-roting cores. HMI connections, Ethernet Switches, and Remote Access Devices will all be mounted based upon the required serviceable clearance, as firmware updates and troubleshooting will occur during production hours.

Logic development is done with an easy read capability. Maintenance groups can trace pump interlocks, drive permissives, alarm handling and manual-auto selection through the logic without having to rely upon the programmer. This includes a simulation of the actual operating sequence prior to being shipped. Once those PLC systems are operating in the US, they provide continuous process control, dependable communications with VFD panels and MCC panels and predictable reactions to any change in load or interruption in utility supply.