MatrixMonitor™ IOM - Rev 4 - 4/11/2013
Page 44
Lubrication Monitoring
MatrixMonitor™ is equipped with a lubrication monitoring system to control the motor bearing
lubrication cycle and reduce the cost associated with this maintenance. The running speed of each fan
array is continuously calculated. The fan speed is calculated from the airflow and pressure rise data
measured for the array knowing the performance of the fans installed in the array. That calculated
speed is checked by comparing it to the vibration measurements for the fans. Every 5 minutes a
calculation is made by the grease life timer to determine the percent of grease life used. This calculation
uses a proprietary formula based on the average fan motor speed in that period. A running total of the
grease life left is kept by the grease life timer. The value is set to 100% when the timer is reset and every
5 minutes, the calculated percent grease life used is subtracted from the running total. When the value
of grease life left is used is equal to 0% the control unit will issue a lubrication warning to tell the
maintenance staff the fan motor bearings need to be greased. When the lubrication has been done the
grease life timer must be reset through the Keypad Display Unit.
The system will predict the hours left until the next required motor bearing lubrication using the life
used calculation. In order to predict the number of hours until the next lubrication the system uses the
real time clock to calculate the elapsed number of hours since the last lubrication. Using this and the
percentage of grease life used the number of hours until the next lubrication can be calculated. The
hours left until the next required lubrication are calculated by the following:
(
)
This calculation results in total elapsed hours
until the next required lubrication. It is not a
running hour calculation. The accuracy of
this equation gets better the longer the
system runs. A typical lubrication cycle can
be several thousand hours of operation. The
unit may run continuously or it may be shut
off at night or on weekends. The running
speed of the array will vary throughout the
day as the building load and outside ambient
conditions vary. All of these factors influence
the grease life used. The longer the monitor
tracks, the more accurate the prediction of
the next grease requirement will be. The “hours left” calculation will bounce around quite a bit until
about half of the grease life is used and will be fairly stable after that as long as the unit operation cycle
is consistent. The equation above gives unusable predictions during the first ten days of operation after
a reset. The “hours left” value is set to 2400 during this period. After 10 days the prediction is made with
the equation above. The result from the equation will improve as more time has elapsed since the reset.
The value should be monitored and the maintenance scheduled at either 20% of life left or 100 hours
