In recent years, improved burner management and combustion control technologies have helped boiler manufacturers produce systems that burn cleaner and more efficiently by enabling more precise control of boiler firing rate, fuel-to-air ratio and excess air. In an age of rising fuel costs and ever-increasing emission regulations, including the reduction of greenhouse gases, it is critical that boiler manufacturers such as Cleaver-Brooks keep their boiler systems updated with control technology that not only addresses efficiency and emissions but enhances boiler reliability and safety.
For many years, Milwaukee, Wis.-based Cleaver-Brooks used a custom-built microprocessor-based control system, called the CB-Hawk, on its steam and hot water boilers. When Cleaver-Brooks learned that its control system vendor was phasing out production and would no longer support the existing technology, the transition deadline presented the company with an opportunity to upgrade its control platform.
Several considerations influenced Cleaver-Brooks during the process of selecting the technology for the upgrade. Early in the evaluation stage, the company decided to build the new control system around off-the-shelf technology and open network communications to improve reusability of code and installation time. To ensure maximum reliability, the control system needed to provide access to real-time operating data as well as historical trending. Also, the company recognized a need in the marketplace for a fully integrated boiler system -- with single-source responsibility for ongoing service, support, training, and replacement parts -- to make the boiler easier to operate, maintain and troubleshoot.
Several automation suppliers competed for the project, and Cleaver-Brooks selected the Allen-Bradley CompactLogix programmable automation controller (PAC) from Rockwell Automation. According to the company, As one of the first small controllers to connect to EtherNet/IP, CompactLogix enables users with less than 2,000 I/O to exchange system-wide information while still providing a 1.5 MB processor and I/O functionality. As part of Rockwell Automation’s scalable Logix control platform, the mid-sized PAC directs all of the burner management functions required for startup, shutdown and online operation of Cleaver-Brooks' CB-Hawk.
According to the company, with RSLogix 5000 programming software, machine builders like Cleaver-Brooks take advantage of built-in function blocks and tag-based addressing to improve time to market. The programming software configures each boiler by enabling and disabling routines. Input modules process signals from field sensors and pushbuttons while the precise control capabilities help increase fuel-to-steam efficiency. Output modules provide signals to final control devices such as vent valves and safety shut-off valves, and to status-indicating lights.
The controller provides both discrete and process control, and allows Cleaver-Brooks to make on-the-fly adjustments and monitor all boiler activity from a central platform. An Allen-Bradley PanelView operator interface provides a graphical representation of process information, allowing operators to change setpoints, monitor alarms, improve tuning parameters and select between automatic or manual control. Cleaver-Brooks also selected the Allen-Bradley PanelView Plus operator interface, which offers additional memory, for its industrial watertube boilers.