Originally Posted by DuckieHo
Hmmm... Sleeve bearing fans on PSUs? PSU are almost always mounted with the fan parallel to the floor. Sleeve bearings are direction sensitive and make more noise/wear out faster if they're not perpendicular to the floor.
FYI: MOST PSU fans are actually sleeve. MOST PSU manufacturers don't tell you when they are, although they're more than happy to tell you when they're ball bearing.
That's one of the main points of the site is to answer everyone's questions about BFG power supplies and power supplies in general and leave a lot of questions unanswered about other PSU brands on the market.
I too have heard on the Interwebs that the make more noise and wear out faster if they're not run pulling away from the floor, but I've yet to see any hard evidence. In fact, common sense would tell me that if the hub is pulled away from the spindle the wear would actually be less because you're reducing friction. Of course, if the fan is pointed up, with the hub pushing into the spindle, I can see how there would be additional wear, but I would also have to believe that the centrifical force of the spinning fan would relieve this stress considerably.
Experiment time! Grab the front wheel off of your bicycle, hold it by the axle and give it a spin. You immediately notice the weight of the wheel being pulled away from the hub and towards the rim. Suddenly the wheel is so light that you can hold it on the tip of your finger.
If there is an effect on lifespan, it has to be so minute that it couldn't even affect MTBF.
Speaking of MTBF: shinji2k's number are pretty dead on. 50K for sleeve and about 75K for ball. The component that's actually most likely to fail over an extended period of time in escalated temperatures... drum roll... capacitors! That said, fan life is almost never calculated into a power supplies total MTBF equation.
The sleeve bearing fans also tend to be quieter at lower RPM's than ball bearing fans. At higher RPM's, the ball is quieter.