Vibration Analysts for Better Cooling Tower Protection

Mechanical Vibration Switches on Cooling Towers: Vibration Analysts Can Make a Big Difference In Spreading The Facts About This Poor Solution

IMI model 685B

Electronic

Vibration Switches Replace

Mechanical Vibration

Switches

TEZZCO's Liberator

The Vibration Analyzer

for Low Cost

Vibration Data Collection & Analysis

Call us for more information

call

(716) 652-5440

e-mail info@tezzco.com

IMI^® is a registered trademark of PCB/IMI including Model 685B series of electronic vibration switches.

VibrAlert^® is a registered trademark of Metrix Instrument Co. Model 5550 is a series of mechanical vibration switches.

Robertshaw^® is a registered trademark of Robertshaw Industrial Products.

Murphy^® is a registered trademark of F. W. Murphy.

Vibration Analysts

Cooling Tower Vibration Analysts

Everyone in our industry knows that mechanical "vibration" switches, if they activate at all, may alarm you of the disastrous failure of cooling tower components: on their best day. You know from the data you have taken from hundreds of machines, maybe thousands of readings, that a mechanical vibration switch cannot sense radial vibration in the speed ranges of cooling tower fans, gearboxes and motors in time to do any good. It is limited to sensing acceleration and activated primarily from shock. Even then, they do not do that with consistency and reliability. Many times the shock must be so severe that machine parts are literally flying. This is a maintenance practice that is not acceptable for any other machine that you work on. Why is it acceptable on cooling towers?

You have seen the data or heard the stories. Example: On one tower in the southeast USA, readings came in at 44 mils displacement at 193 Hz (fan speed) taken as an axial reading on the motor outboard bearing. THE TOWER WAS VISIBLY MOVING. A mechanical vibration switch would have to be set for under 0.03 Gs to do any good! What's your guess of the setting on the average mechanical vibration switch? We estimate at 1G or higher just because that's likely how they come from the factory. Worst case, 1 G is not enough to get past the bump at startup and they are cranked up higher to avoid the nuisance. That's a long way from 0.03 Gs and cooling tower protection by any reasonable definition.

You are invited to a free download of the paper "Roulette and Mechanical Vibration Switches: What are your Odds?" It is meant to help make the case for change with management. We would like to hear your comments; share some stories.