Automated Packaged Boilers Boost Brewery
Reliability

The automation of five packaged boilers at a major U.S. brewery has quickened response to brew and mash kettle steam loads, boosted boiler reliability, helped bring the boilers back to their nameplate ratings, and no doubt raised thermal efficiency. The upgrade extends the life of the boilers and helps assure maximum brewery output. The automation replaced 1970s era pneumatic and relay
logic controls.

Aging Controls Failing

By late 1999, the five boilers' pneumatic combustion controls and relay-logic burner management systems were beginning to jeopardize production. A decision was made to upgrade by installing PlantWeb® scalable, field-based architecture consisting of compact and modular process controllers, PC workstations, and graphical configuration software networked with FOUNDATION™ fieldbus instruments, transmitters, and valve and damper positioners . All valves were either replaced or rebuilt, and dampers were renovated. The controllers and workstations are networked on the automation's Ethernet LAN.

This architecture allows combustion control, burner management, and an intelligent Plant Master to be tightly integrated and to share a global database, common operator interface, standard configuration language, and spare parts. Because burner management is not performed by a separate PLC, no time-consuming and error-prone mapping between PLC and HMI databases is required. Communications between burner management and combustion take place over the automation's 10 Mbps control network, not a serial link.

Fieldbus Provides Many Advantages

Commissioning, loop checking, and calibrating the fieldbus instruments took only two hours per boiler and was performed entirely from a workstation. When wired up, the devices simply appear live on the configuration -- no ringing out wire pairs, lugging a calibrator up and down ladders, inserting 4-20mA signals, etc. Automatic calibration exercised the devices and set the values. The fieldbus instrumentation’s built-in diagnostics enables troubleshooting from a workstation, which should speed instrument and boiler repair.

Necessary Mechanical Adjustments Highlighted

Characterizing the boilers during startup was likewise enhanced by the automation and fieldbus instrumentation. Tests were done under manual control at 10% increments from 30% to 100% of load while monitoring O2 analyzer to establish the fuel-air and firing-load profiles.

Data trended by the automation during the characterizations helped expose mechanical problems in several boilers, such as flame instability at low outputs, capacity problems in combustion air and fuel flows, and excessively fluctuating drum levels. By tuning operation of boiler feed pumps, fixing burner dampers and installing fieldbus positioners, adjusting damper linkages, and tightly tuning the automation's three-element drum level control, the boilers were restored to near their original nameplate ratings.

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