need help with this #@!%&# fan

S

sellersrodshop

every time i think i've about fixed all the bugs in the new shop, something else happens... now its an issue with my exhaust fan. i "think" i have an idea, but will lay it all out first in case i'm missing something. first off, a few weeks ago, while i was shooting, the belt started squealing. between coats, i climb up in the attic & give it a quick snugging up which quieted it down. last week, the belt came apart. started hearing slapping sounds & it was threads on the belt slapping around . i figured this was my fault, as i didn't take a ruler up the first trip so may have gotten the pulley alignment off a bit when i tightened it. long story short, got a new belt, installed it, tightened it up using a ruler to make sure the motor squared up & aligned properly & today it started squealing again.... made another trip upstairs & tightened it a bit at a time. each time, it would be quiet long enough for me to get my tools picked up & back to the ladder, then it would start again. tightened the belt to the point where it wouldn't turn the fan at all, so know it isn't a "slop" issue. also noticed when it started making noise, i could turn it off for a min, turn it back on & it would be quiet for about 1-2 mins, then get noisy again. i repeated this a few times with same results.

here's what i'm thinking, if its actually possible. my filters are dirty & ready for a change. is it possible that with the restricted airflow of the dirty filters, its actually creating an airflow drag thats suppressing the fan blade & causing the belt to slip? i'm going to do a filter change tomorrow & see what the results are but i anyone has any ideas, feel free to post them up.

oh, the fan is a dayton tubeaxial:

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Did you check the bearings in the fan? If they are going bad and the fan is starting to lock up it will eat threw belts all day. The tighter you make the belt the more pressure you are putting on the bearings.
 
i've had the same fan set up for many years . one thing i found is over time the blade will slide down on the shaft and put it in a bind. make sure it turns freely. if not loosen the blade and pull it up some. the one in my booth i bought in 88 so they are good fans.
 
Bushings or bearings on the shaft, if bushings, they may have inadvertently been left dry at the factory.
 
sellersrodshop;16408 said:
is it possible that with the restricted airflow of the dirty filters, its actually creating an airflow drag thats suppressing the fan blade & causing the belt to slip?
Click to expand...

Don't know if it is the problem, but yes, with a vane axial fan, the load increases even if the airflow decreases due an increase in resistance to flow.
 
Axial flow fans should be using a bearing designed for lateral loads. A standard sealed ball bearing is not. You have no idea what that manufacturer used without having the number on the outer bearing race.


side note: fans for the big boys. 100,000 lb alum annealing furnaces.
I have replace many 42" dia. 8 blade, vertical shaft axial flow fans that use a radial load ball bearing as the upper bearing and the lower bearing is a bronze bushing, enclosed in a water jacket and supplied drip oil through a tube system. Keep these bad boys properly lubed and having a proper water flow and they will run 24/7 for years with the lower "water" bearing operating in a 900f environment.
 
think i may have figured something out... after studying this thing a bit today, i went & picked up another belt that's just a little bit narrower & seats deeper into the pulley. i tafter inspecting the old belt, it seemed to have some pretty premature wear on the sides & didnt seem to seat well in the fan pulley. i think over time, as the belt would wear, it would seat deeper in the pulley thus loosening the tension. we'll see what it does for a few days & hope this fixes it...
 
My fan (Dayton / tube) did the same thing after 25+ years of use. It was one of the ball bearings in the motor.
 
sellersrodshop;16489 said:
think i may have figured something out... after studying this thing a bit today, i went & picked up another belt that's just a little bit narrower & seats deeper into the pulley.
Click to expand...

I was kind of wondering if the belt fit right, I think you may be on to something.
 
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