The boiler controls showed air dampers changing position. In the field, those dampers were not moving. During a biomass boiler tune-up at a wood-products facility, CPE found that mechanical faults were limiting what control adjustments could achieve.
Tuning the equipment that still worked reduced measured carbon monoxide (CO) by 51% in one boiler. The assessment also identified repairs needed to address the remaining problems.
Why the equipment response mattered
Overfire-air dampers regulate air entering above the fuel bed. Their actuators, the devices that move them, reported position changes even though the dampers remained stationary. A change on the control screen therefore did not mean the air supply had changed as intended.
Field checks also found air leaking into the multiclone dust collector, failed oxygen analyzers and deteriorated insulation. These faults affected the information available to operators and the equipment available for combustion control.
What tuning achieved
CPE adjusted the functioning equipment during the Boiler MACT tune-up. CO fell from 943 to 463 parts per million by volume, measured on a dry basis and corrected to 3% oxygen. Nitrogen oxides (NOx) remained stable under the tested conditions.
Control-loop tuning also improved the response of fuel feeding, steam-temperature control, oxygen trim, boiler pressure and furnace draft. These changes improved operation within the limits of the equipment that was working.
What still needed repair
The lower CO reading did not resolve the stuck dampers, failed analyzers, air leaks or damaged insulation. Those findings remained maintenance priorities. The plant received both a measured tuning result and a repair list to address the remaining constraints.
For a plant planning a boiler tune-up, the practical lesson is to verify that dampers move, analyzers provide usable readings and the equipment responds before relying on control-screen indications alone.
CPE's combustion assessments combine operating adjustments with field checks so the plant receives a tuning result and a practical maintenance priority list.