Page 235 - Intro Predictive Maintenance

Table 10–4 Common Failure Modes of Centrifugal Fans

THE PROBLEM

Insufficient Discharge Pressure Intermittent Operation Insufficient Capacity Overheated Bearings Short Bearing Life Overload on Driver High Noise Levels Power Demand Excessive

THE CAUSES High Vibration Motor Trips
Abnormal End Thrust
Aerodynamic Instability
Air Leaks in System
Bearings Improperly Lubricated
Bent Shaft
Broken or Loose Bolts or Setscrews
Damaged Motor
Damaged Wheel
Dampers or Variable-Inlet Not Properly Adjusted
Dirt in Bearings
Excessive Belt Tension
External Radiated Heat
Fan Delivering More Than Rated Capacity
Fan Wheel or Driver Imbalanced
Foreign Material in Fan Causing Imbalance (Plate-Out)
Incorrect Direction of Rotation
Insufficient Belt Tension
Loose Dampers or Variable-Inlet Vanes
Misaligment of Bearings, Coupling, Wheel, or Belts
Motor Improperly Wired
Packing Too Tight or Defective Stuffing Box
Poor Fan Inlet or Outlet Conditions
Specific Gravity or Density Above Design
Speed Too High
Speed Too Low
Too Much Grease in Ball Bearings
Total System Head Greater Than Design
Total System Head Less Than Design
Unstable Foundation
Vibration Transmitted to Fan from Outside Sources
Wheel Binding on Fan Housing
Wheel Mounted Backward on Shaft
Worn Bearings
Worn Coupling
120-Cycle Magnetic Hum
Source: Integrated Systems, Inc.