Re: Drive Pulley To Belt Friction Coefficients
Just a few notes on your concept:
1. Starting time makes a big difference on the acceptable dynamic friction or allowable slip during starting verses steady-state.
A 10-15 second start with a friction factor of f=0.04 is far more acceptable that a 200 second start with the same.
2. The level of pulley lagging heat and wear must be factored into the equation for rubber lagged assemblies.
3. Your slimey criteria needs some work. They seem too high allowables for red mud fines or slimes.
This will likely produce some operator responses. ■
Re: Drive Pulley To Belt Friction Coefficients
Derek
Nice work. I generally agree with your values.
I find it interesting that getting the belt suppliers or the lagging suppliers to commit to friction values is like pulling teeth.
Whilst the published values are probaly conservative, they are well worth sticking to (no pun intended). I've heard of men having to shovel sand into a drive pulley/belt interface to prevent slippage - doesn't sound pretty.
The good news is that in many (or even most) cases other factors such as belt sag make the lagging friction less critical. ■
Drive Pulley to Belt Friction Coefficients
Trying to get a summary of typical criteria to use for the drive pulley to belt corefficients of friction in mineral processing plants.
The main variables affecting the coefficient of friction are the type of lagging, the presence of water and mud in mineral plants, the operating condition, and the type of takeup (gravity or fixed).
The friction coeffficient used can have a significant impact on the takeup weight, belt tensions, and hence belt ratings, pulley diameters, and pulley shaft sizes. Higher tensions affect mean higher structural loads.
Here are some typical values I've seen, and in some cases used. I'd be interested to hear values other people use.
UNLAGGED PULLEYS
Dry:
Starting - 0.28
Running - 0.25
Braking - ???
Wet but clean (Not normally used):
Starting - 0.11
Running - 0.10
Braking - ???
Wet but slimey:
Starting - Not recommended
Running - Not recommended
Braking - Not recommended
LAGGED PULLEYS, DIAMOND GROOVED
Dry:
Starting - 0.0.38
Running - 0.35
Braking - ???
Wet but clean:
Starting - 0.38
Running - 0.35
Braking - ???
Wet but slimey:
Starting - 0.35
Running - 0.30
Braking - ???
CERAMIC TILES BONDED TO RUBBER LAGGING
Dry:
Starting - 0.9
Running - 0.8
Braking - ???
Wet but clean:
Starting - 0.5
Running - 0.45
Braking - ???
Wet but slimey:
Starting - 0.38
Running - 0.35
Braking -
Notes:
1. These values are typical for belts that have been in operation for some time. Values for conveyors with new belts and lagging may be significantly higher.
2. Values of coefficients can be higher at startup. Values have typically been increased by 10 % for this condidtion.
3. Values are given assuming a gravity takeup. Reduce all values by 10 % for fixed takeups.
4. Cannot recall criteria to use for braking. Someone may be able to help.
5. I'd be interested to see values used in the current CEMA manual.
References:
1. Apex Fenner catalogue. Feb 2002
2. Dunlop Manual. March 1977 ■