Wireless Condition Monitoring

Fan gearboxes and circulation pumps at a 36MW power station with four cooling towers is monitored with the Maintenance Watchdog System. Two wireless accelerometers are mounted on each gearbox inside of the cooling towers. The tower circulation pumps are not difficult to access, but because they are within range of the transceiver, four accelerometers per pump can also be monitored. Each wireless accelerometer provides several vibration readings per day for consistent analysis.

Issues:

• Criticality - Profitable operation requires full plant capacity during peak demand times, and all four cooling towers are required to achieve full capacity. Outages need to be scheduled in advance during off-peak times.

• Safety - In the past, a technician climbed into the towers to take vibration readings with a portable data collector. The technician radioed the control room to turn off the cooling tower fans to gain access to the internal gearboxes. When in position, the technician radioed the fans to be turned on in order to obtain vibration readings.

• Cost - As an alternative to taking readings inside the cooling tower while it is in operation, permanently mounted accelerometers could have been installed and run to a remote switchbox. The accelerometers would require at least 50' of moisture proof, corrosion resistant cables. The high cost of installing and maintaining the hard-wired system justify the use of wireless accelerometers.

• Environmental - The cooling tower water is very caustic. Sulfuric acid and bromine are added to control the properties of the water. The accelerometers must withstand continuous spray of this caustic water solution and must have the appropriate corrosion resistance.

High-speed printing press gearboxes and motors are monitored at a 1 million book per day printing and binding facility. Wireless accelerometers are mounted on a gearbox and motor behind the equipment guards. The accelerometers provide one reading per day on critical components to significantly reduce unplanned maintenance downtime. Problems are caught early before they have a chance to propagate to other equipment or affect product quality.

Issues:

• High speed - Due to the high-speed nature of the printing presses, downtime is very expensive and problems propagate very quickly within the presses.

• Accessibility - Safety guards prevent accessing the rotating equipment on the printing presses with portable data collectors. Permanently mounted accelerometers with cables and switchboxes would be required to take readings.

• Collection interval - Because only one technician is available to collect data, the frequency of readings had been limited to 6-8 weeks. The facility is subject to unscheduled downtime due to the rapid development of problems in the presses that are not caught through the infrequent route running.

• Environmental - The printing press is a cramped, dirty environment that is subject to frequent cleaning with solvent agents. The accelerometers must withstand spray of this caustic solution and must have the appropriate corrosion resistance.