L10 Test Procedure A. Select a random sampling of 50 high-speed fans. After running the fans for 3-5 minutes, characterize each unit’s performance against the specification for rated speed, rated voltage, rated current, noise level, and appearance.
B. Place the sample group into a 70º C chamber running the fans continuously at the rated voltage in free air.
C. Record the rpm, voltage, and current at 24 hours, 48 hours, 96 hours, 168 hours, 336 hours, and finally at 168-hour increments until testing is complete. Testing is deemed complete when 8 samples record a primary fan failure.
All fans will be checked daily to confirm continuous operation. If a failure occurs before the data collection date, record the actual time of the fan failure.
D. As each unit fails an evaluation of the failure should be done. If the failure is deemed to be a primary failure, then this data will be used for L10 life projection calculations.
L10 Life Calculation A. Using the Weibull Distribution Curve presented in “The New Weibull Hand Book” Fourth Edition, by Dr. Robert B. Abernethy, plot the percent failures on the y-axis and the hours for failure on the x-axis using Weibull paper.
B. Draw a straight line that best represents the actual slope of the data plotted.
C. At the 10% location on the y-axis draw a horizontal line until intersecting the data line. At that intersection draw a vertical line perpendicular to the 10% horizontal line. At the point where this vertical line intersects the x-axis, L10 Life data is projected for the fan samples at 70º C.
D. Using the Temperature/Life factor, project the L10 fan life for 60º C, 50º C, 40º C, 30º C, and 25º C.
Fan Failure Terms Fan Life – The period of time the fan runs continuously without stopping.
Fan Speed – The number of rotations of the fan rotor per minute (RPM) at rated voltage in free air.
Fan Failure – The point where fan speed (RPM) changes 10% from nominal start up fan speed (RPM). The current increases more than 10% from the initial readings.
L10 Life – The number of hours when 10% of the fans fail, or 90% survive.
Primary Failure – When the fan unit records a fan failure that is caused by bearing system failure.
Temperature/Life Factor – The factor that is used to determine increased fan life for operation temperature drops. Temperature / Life factor data has been established based on 60º C, 50º C, and 40º C testing. Temperature/ Life factor: =1.5 /10 ºC (1.5 per 10 º C drop in operational temp).