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Large Fans with Journal Bearings - Vibration Monitoring for Large Fans with Journal Bearings, FD, PA, ID FANS
Last Updated: 05/23/2017
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Machinery Applications Include: FD Fans, Forced Draft Fans, PA Fans, Process Air Fans, ID Fans, Induced Draft Fans, Boiler Fans, Power Generation, Steam Power Plants, PdM for Fans, Fan Condition Monitoring, Fan Vibration Monitoring, Fan Protection System, Fan VMS.

Large Motor Driven and Turbine Driven Fans are used for Forced Draft, Induced Draft and Process Air in Steam Power Generation. These Fans can range from a few hundred to several thousand horsepower. Speeds are moderate and usually between 300 and 900 RPM. Due to the high horsepower and heavy loading Journal Bearings are prevalent. It is recommended that Journal Bearings be monitored with Proximity Probe (Shaft Relative) System. Experience has shown that the Fans Journal Bearings themselves alternately can be monitored radially using Accelerometers. This is due to the heavy rotor/light casing ratio of the Fan assembly and the flexibility of the bearing mounting pedestals. This exception is for the Fan only and Motors, Turbines and Gears should be monitored using Proximity Shaft Relative Systems. The Fans Thrust Bearing should also be monitored with Proximity Probe Systems.

Large FD, ID, PA Fans

PdM or Data Collector BOM:

A Stand Alone PdM or Data Collector System or BOM (Bill of Materials) is not recommended for Journal Bearing Critical Machines. A PdM or Data Collector program can be done supplementary or in conjunction to a Vibration Protection System. STIís Vibration Monitoring Systems below provide BNC connectors to connect Analyzers or Data Collectors to the raw (buffered) signal for each sensor.

Protection System BOM using Plant PLC or DCS:


The Protection System BOM (Bill of Materials) meets the requirements of API-670 and provides a simple low cost approach to Vibration Monitoring making use of the plants PLC/DCS or Historian for alarming and trending of values. A 4-20mA signal is provided for connection to local Field IO. The STI CMCP500 Series Transmitters connected to the machine mounted proximity probes and accelerometers provide Signal Detection, Signal Integration, Power Regulation, OK Circuitry, Timed OK Danger Defeat, Range Selection and Sensor Power.

Protection System BOM (Stand Alone):


The Stand Alone Protection System BOM meets the requirements of API-670 and provides all the features of the above Protection System with the addition of Relay Modules and Displays. OK, Alert and Danger Alarms and 5 amp Relays are provided for each channel. The ability to select alarm delay, trip multiply, latching or non-latching relays are provided. Terminal for remote reset is also provided. The CMCP5304 is a complete system simply supply AC line power and connect sensors.

Recommended Installation Accessories (All Systems):

The following are STIís recommended Installation Accessories. Quantities vary as shown depending on the BOM selected above. More details and instructions on Accelerometer Installation can be found under our Application Notes at this link: http://www.stiweb.com/appnotes/Accelerometer_Installation_Guide.html



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