The bearings of all the belt driven accessories will have excess strain and likely fail prematurely.
Reasons: Cheap Belt Too tight
Two reasons why your alternator belt is breaking is: Your alternator belt is too tight, or you are using a belt that is old and worn. I cannot answer your question fully without seeing the vehicle. Sorry.
Because the alternator puts a load on the engine of several horsepower, the belt must be very tight. However, if it is too tight, the bearings of the alternator shaft will wear out quickly. To tension the belt properly, adjust until there is about 1/2 inch of play in the center of the longest span. If this does not stop the squealing, the belt may have been glazed from being too loose, and needs to be replaced.
to change the alternator belt, there is tow way. if the car is equip with a/c you need first to remove the a/c belt and then remove the alternator belt. both belt are put in place the same way, so you'll might have to do one or two. first, you have to untight the bolt over the alternator and let it in place. second, you have to untight the bolt under the alternator and let it in place. with your hands, you can rotate the alternator near the engine. once the belt is free, replace it with the new one. make sure the belt is place in the right pully slot and is correctly alligned. to tight the belt you will need to pry the alternator with a prybar. hold the tension with one hand and tight the bolt over the alternator with the oder hand. you can now stop prying and tight the bolt under the alternator. now check the belt tension. to have a good tension on your belt you can use a simple 12 inch wood rule (like in junior school) place the rule on the belt and with your hand pry the belt. for a proper tight strenght the belt should move about 1-2 inches. if its too tight the belt life will decrease and if it is to tight it will not rotate the alternator properly.
Excessive wear on water pump, alternator, power steering pump bearings
Incorrect belt, too tight or too loose belt. Should be 1/4 inch deflection at the mid-point of the belt. Pulleys out of alignment or warped.
Loosen the belt tensioner. The belt should not be tight at all.
either too tight or to loose, need about 8mm of give between alternator and drive pulley
"First Remove the Tension bolt from the alternator and remove." "Next take a hammer and gently tap the alternator down" "Do the same with the Tension Mount" "After realigning the alternator and the Tension mount replace the bolt" "BE CAREFUL NOT TOO TIGHT ON THE BELT OR YOU WILL RUIN THE BEARINGS" "GOOD LUCK"
If the alternator is bolted on too tight on its bracket,then it will cause the alternator to have a "bend" so that the clearance between the moving parts is reduced and the moving parts eventually jammed.
Alternator belt is probably loose and slipping. If you can turn the alternator by hand and the belt slips its too loose. Retension alternator belt
because its too tight