Using a BAS for process control
Building automation systems are found in nearly every type of industrial plant handling a variety of tasks. But their diversity is perhaps best exemplified in an application that uses a BAS for process control.
The installation is a retort-in-place system specially designed for the thermal desorption of the mercury found in fluorescent lamps. The recycling process requires precise control of temperature and time to achieve consistent results. Using a vacuum process, the technique separates out the mercury, which is collected and sent to a distiller where it is purified for reuse.
BAS control technology was employed primarily because the mechanical contractor installing the retort system was familiar with it and believed the processing equipment would lend itself well to control by a BAS. The firm was already experienced in using a BAS to oversee such an operation, having installed it in another application 3 yr ago.
The DDC-based BAS system provides continuous and reliable control of operating conditions and temperatures. It includes a touch screen display and access to all process variables; remote and onsite around-the-clock monitoring of process alarms; and onsite monitoring from a PC or dumb terminal. Open net
working arrangements allow device-level controls from a variety of manufacturers to be incorporated into the system.
It also permits large volumes of information to be transmitted over two wires for maximum data collection and analysis at the greatest efficiency. Password security protects data and limits access to proprietary information.
Designed to maximize plant and operator safety, the BAS enables the process to operate unattended and lets the operator pause or stop the process should any measured variable exceed allowable limits. Alarm conditions are displayed on the touch screen. Dial-out alarm messages directed to a remote monitoring facility simplify the handling of problem situations. Redundant electrical and mechanical controls for high temperature, pressure, and flow levels enhance safety and ensure compliance with federal and state hazardous waste handling regulations.
Notes Bob Abele, one of the senior engineers on the project, “Doing both the mechanical contracting on the process equipment and installation of the BAS have the advantage of teaching us how to troubleshoot the system, how to make things work. Being involved in both sides helps us know what is needed and how to do it.”
Two systems are now in place and operating successfully, one in Phoenix and a second in Indianapolis. Both are monitored remotely in real time.
Remote access monitoring and control of the equipment have proved advantageous from startup, allowing installing engineers to change or override parameters without traveling from site-to-site. The remote features were especially helpful for initial troubleshooting when a large number of alarms can generally be expected.
Information for this section was provided by Herman Bogot & Co., Park Ridge, IL, installers of the system. The BAS in the system is from Circon Technology Corp., Delta, BC, and uses a Lonworks network from Echelon Corp., Palo Alto, CA.