Knowledge Base:  
Cooling Towers - Vibration Monitoring for Cooling Tower Fan Motors
Last Updated: 05/22/2017
Download the PDFCooling Tower Fan

Machinery Applications Include: Cooling Tower, Cooling Tower Fans, Cooling Towers with
Jackshaft, Cooling Tower Gearbox, Condition Monitoring, Vibration Monitoring, Protection
System, VMS

Cooling Towers are made up of a Motor, Gearbox, Fan and connecting Jackshaft. The Gearbox translates the motors 1500/1800 RPM to a lower RPM for the Fan. Fan Speed varies from less than 100 RPM to a few hundred RPM depending on diameter. Rolling Element Bearings are standard and should be monitored using properly placed Industrial Accelerometers. Care must be taken to waterproof all Accelerometer connectors by flooding with Silicone Grease. For Monitoring Systems the LF (Low Frequency) option should be selected for the low speed gearbox shaft.

Only “X” or Horizontal Accelerometers marked in Red are recommended for Full Time Vibration Monitoring (Protection) System. Walk Around Data Collector or PdM Programs usually require “X” Horizontal (Red), “Y” Vertical (Green) and “Z” Axial (Yellow) Sensors for analysis. When economic decisions must be made to reduce sensor count due to the size or criticality of the Motor Driven Pump “X” or horizontal sensors should be installed first as they are closer to the load zone of the bearing and in direction of freedom of movement.

Cooling Tower Fan

PdM or Data Collector BOM:

Recommended for walk around Data Collector Programs where the number of sensors or vibration measurement points is based on the current established collection and analysis techniques. Permanently mounted Accelerometers provide a more reliable and repeatable reading and the local BNC Switch Box allows for faster, safer and more convenient data collection. STI Products work with all manufactures data collectors and analyzers.

cooling tower bom1

Protection System BOM using Plant PLC or DCS:

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 accelerometers provide Signal Integration (g’s to Velocity), Power Regulation, OK Circuitry, Timed OK Danger Defeat, Range Selection and Constant Current Sensor Power.

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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.

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Recommended Installation Accessories (All Systems):

The following are STI’s 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:

Cooling Tower Fan

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