Hardy Instruments has provided solutions to companies in the Energy Industry for the vibration monitoring of Cooling Tower Fans and of Higher Speed blowers systems.
In monitoring the condition of a cooling tower fan, Continuous vibration monitoring is the best methodology as some types of failures occur suddenly. The most common type of sudden failure is broken blades (part or whole). Others are usually structurally related. Mechanical drive system problems can be seen, most of the time, in a periodic monitoring program, before they become critical.
Many cooling towers were originally equipped with mechanical switches (commonly refereed to as "kick" switches or "earthquake" switches). These are often tied into the motor drive power circuit and will shut down a cell in a tower if activated, offering protection against catastrophic damage. Often the vibration switch will not respond when it should for a variety of reasons. For example, if a switch is mounted on a wooden cross member that has loosened, it may not respond to a loose coupling bolt even if it causes an unbalance condition. The vibration switch does not offer any protection in this case. Recognizing this fault, many users have replaced these devices with a continuous monitoring device.
A continuous monitoring system, the kind used to monitor critical machinery, offers several advantages for monitoring cooling towers. One advantage is the sensors can be mounted directly on the bearing support parts on the motor and the gear so bearing condition, as well as casing vibration can be measured. Also, two levels of alarm can be set so operators can be made aware of potential problems at early stages of development before a condition becomes critical. The second level of alarm can be used for shutdown in the same manner as did the vibration switch. The problem with conventional continuous monitoring is simply that it costs too much and is hard to justify.
Using The HI 5500 Modules:
A modular continuous monitoring system, such as the Hardy Instruments HI 5500 Series, offers low cost "building blocks" that are ideally suited to monitoring cooling towers. The modules include vibration detection modules, dual set point modules, and relay modules. Other modules are available but these three types can be combined to provide a very reliable continuous monitoring capability for cooling towers.
The HI 5701 Solution
If the fan or blower is operating at speeds of 300 RPM or above, the HI 5701 Transmitter may be an ideal, inexpensive solution. This solution is an all-in-one rugged (Hazardous Design) package consisting of the accelerometer and the signal conditioner. Thus, you simply mount the transmitter, wire the output, and you're up and running.
The HI 3600 Solution
If you have a bank of fans or blowers and wish to monitor all of thes points, and tie the signal into a main control room via any network, including wireless, the HI 3600 Machine Monitor is the ideal solution.
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