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August 2, 2017

How long should your fan run for?

We all know we shouldn’t wait until our cooling fans come to a complete stop before replacing them on our Motor Drive/Power supply units. By not having the proper cooling ventilation on our equipment it can cause overheating causing electronic devices to malfunction or fail resulting in severe damage to the Drive/Power Unit. .

So…what are some of the steps to prevent these types of failures

We thoroughly inspect all our products cooling fans/blowers by visually inspecting them for any signs of heat stress, environmental contamination and listening to any loud noises due to wear on the bearings or weakened housing. We also pay attention to the fan/blower date code to determine the age of the fan and based on the operating hours of the unit we could determine how long the fan has been in operation, where we can make a decision if the fan should be replace.

The fan’s life line is typically defined in the air moving industry by the use of two terms: “L10”-the life of the bearing and MTBF(mean time between failures).

Fans typically fails due to the bearing system built into the fan. We can expect as an engineer a useful life of 60,000 – 70,000 hours (L10) under normal conditions (-40C – 50C at 75% Relative Humidity). As a general rule however the life expectancy will normally increase when the temperature of the environment is cooler. We also need to consider the Switch-on Condition (CD,ID or SD) which puts a strain on all devices and reduces the service life.

The L10 is defined as the number of hours after which 10% of the fans in operation would be expected to experience a bearing failure. We can calculate the data using Weibull statistical analysis to obtain a failure distribution prediction. Usually what causes the bearings to fail is due to lubricant degradation over time, which at higher temperatures and high humidity can speed up the failure rate. The L10 bearing life numbers are provided at a specific ambient temperature. (See product manufactures specs).

The MTBF are predictions based on assumed constant failure rates over the useful lifetime of electronic components. These predictions are usually based on MIL-HDBK-217 or Bellcore TR-332; (Reliability Prediction Software), but because mechanical or electromechanical components like bearings and motors do not have constant failure rates over time, makes it difficult to interpret real number calculations. Many manufactures will quote a 200,000 +/- hour life expectancy by referring to MTNF curves rather than the more common L10 curve.  

Here is a ratings chart for a SEPA type fans:

There are some factors to consider when purchasing a fan/blower like the IP rating (International Standard) that pertains to rating motors for the effects of dust. Moisture protected motors are built to an Internal Protection Classification of either IP44 or IP54.

Contact us for any fan/blowers information need, as we use OEM parts when we sell or repair our DRIVE/POWER UNITS.