Overfire Air Fan

SMARTdiagnostics detected rising vibration on a critical Overfire Air Fan. Inspection revealed a failed coupling and bearings installed incorrectly, restricting thermal expansion. After replacing components and realigning the unit, vibration returned to normal. Early detection prevented failure and saved 168 hours of downtime, resulting in $376,393 in savings.

DETECTION: SMARTdiagnostics identified elevated vibration on both the fan and motor. The system’s data and SENTRYsolutions analysis suggested possible load or rate change issues, prompting a detailed inspection.

ACTION: Technicians replaced the failed coupling, corrected the bearing configuration so only the inboard bearing was fixed, and realigned the fan assembly. The asset was then verified as healthy through follow-up data.

IMPACT: The proactive repair restored normal operation, prevented a catastrophic failure, and avoided 168 hours of downtime—saving the customer approximately $376,000.

Introduction

Overfire Air Fans are crucial for optimizing boiler and furnace combustion by improving efficiency and reducing harmful emissions. By strategically injecting air into the upper regions of the furnace, Overfire Air systems (OFA) promote turbulent mixing of fuel and air, ensuring more complete fuel burnout and a cooler combustion process.

Overfire Air Fans also help maintain environmental compliance by preventing non-condensable gases (NCGs) from escaping and instead recycling them into the furnace, which supports adherence to regulations. Because of their importance, ensuring this equipment is running in healthy conditions and avoiding unplanned downtime is critical.

The Problem

KCF Technologies’ SMARTdiagnostics machine health platform flagged an increase in vibration on a critical Overfire Air Fan, with high velocity noted on both the motor’s inboard and fan’s outboard components. Based on this data, SMARTdiagnostics recommended that the team conduct a comprehensive inspection of the asset, focusing on lubrication, the fan rotor, and bearings. Additionally, their dedicated SENTRYsolutions analyst suggested reviewing how velocity spikes might be related to load or rate changes. Because rate changes and damper swings would cause vibration levels to increase, SENTRYsolutions advised treating the equipment gently to prevent further damage while the root cause is being investigated.

During the inspection, the customer uncovered several developing issues. The flexible element on the coupling had failed; the fan inboard bearing was damaged, with grease burnt to a black color from friction, and both the inboard and outboard bearings had fixed locating rings installed. With both bearings being fixed, the shaft could not thermally expand. This restriction created excessive pressure and friction, ultimately driving the developing fault.

The Solution

To correct the issue, the customer replaced the flexible coupling element, replaced both fan bearings with only the fan inboard bearing being fixed, and realigned the unit before returning it to service. Comparing data from before the remediation to after verified that the asset had returned to healthy operating conditions. With early warning from SMARTdiagnostics, this fault was discovered before a catastrophic failure could occur. By proactively identifying and resolving this issue, the customer avoided 168 hours of unplanned downtime, resulting in an estimated $376,393 in customer savings.

Introduction

The Problem

The Solution

$376,393

168 Hours

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