Distributed Control Systems Primer

As water and wastewater treatment plants grow in both size and complexity, so does the need to control equipment that make up the unit-operations of that plant. Distributed Control System (DCS) is a control system method that is spread, or distributed, among several different unit processes. These processes may be related, as in a water treatment facility, or unrelated, as in a manufacturing plant where many different products are fabricated.

The DCS is typically a hard-wired system and exists within finite boundaries, such as a process plant or within a factory. Wired systems are reliable and are well suited for the typical process environment where flexibility is not an issue. Wireless systems are starting to become popular and hold the promise of improved flexibility in both physical and logical layout of the facility. An entire process may be retooled to the extent that several parts of the process will be physically moved or removed. Using wireless, system reconfiguration is as simple as disabling the station address or downloading the suitable database.

Whether wired or wireless, distributed control systems offer the advantage of centralized control, while retaining the capability of distributed, or local control. True distributed control systems use localized control, which is in turn controlled by the operator located at a central location. Distributed Control Systems consist of the following:

* Remote control panel
* Communications medium
* Central control panel or facility
* Control, interface and database software