Originally Posted by Saviz

Idler Friction Factor for Loaded and empty conveyor

Dear Experts,

I have a feeling that, idler friction factor may depend on load which apply on idler.

But, in any handbook, manual or even test report from idler manufacturer, this difference did not enter into calculation. This difference will effet take up calculation and power calculation.

Is there any reference which consider this difference into calculation? or difference has not considerable impact on calcs?

Many thanks for your cooperation.

Regards

Saviz

The friction factor is a dimensionless factor and is merely a ratio of the friction force : the load on the idler.

The higher the load, the higher the friction force as described by the friction factor. This is where it comes in. ■

Hi there Savis..

Indeed, ISO 5048's "f", the artificial friction factor, does increase with load.

This is why so many designers make the horrible mistake in thinking that if they have a variable speed conveyor, and always run it at a speed at which it is full, they will save power!

(To my surprise, I have even seen this quoted in a Beltcon Paper)

Not so, most of the time.

The graph of friction factor vs load is an significantly exponentially increasing curve.

(The factor also increases as the ambient temperature decreses.)

For shorter conveyors, you also have to include for the effects of the "C" factor this compounds the problem of high "f" factors, for always running the belt full, as the two are multiplied together.

For normal designs therefore, always try for a fixed speed installation, use a well selected "f" for the conditions, and you will be fine.

Cheers

LSL Tekpro ■

The idler drag has many components and depends on:

1. Material load as you and others note

2. Bearing size

3. Belt speed

4. Grease type

5. Grease temperature

6. Seal type - horizontal or vertical labrynth w/ contact or no contact

7. Idler trough configuration

8. Note: load is dependent on material, vertical curves and horizontal curves

9. Belt tension associated with curve location

Idler drag is a part of the loss in DIN f from DIN 22101.

Major loss (60-70%) in DIN f is from rubber's viscolelastic indention hysteresis loss, excluding lift force ■

When you note the hydro-coupling loss, this is not a part of the DIN f or other so called friction losses. Hydro-vicous loss in a only the mechanical loss due to shearing of the fluid within the coupling.

It is not a belt line loss as referenced in DIN f. Neither is the pulley drag loss of the bearing. The loss from bending the belt over the pulley some consider a belt related friction loss.

Then you have the belt related losses:

1. Type of rubber compound and its viscoelastic properties during operation

2. Thickness of belt cover in contact with the idler roll

3. Idler roll diameter

4. Idler spacing

5. Idler trough configuration that influences the pressure between belt and idler

6. Belt construction bending stiffness

7. Steel cord or fabric tensile construction

8. Material loading crossection - determining the pressure distribution against the idler roll

9. Vertical and horizontal curve pressures between belt and idler

10. Belt tension and sag

11. Belt speed

12. Belt temperature

13. Steel cord diameter and pitch within belt construction

14. Then their are the pipe belt construction properties

I doubt I have noted all. ■

Originally Posted by nordell

When you note the hydro-coupling loss, this is not a part of the DIN f or other so called friction losses. Hydro-vicous loss in a only the mechanical loss due to shearing of the fluid within the coupling.

It is not a belt line loss as referenced in DIN f. Neither is the pulley drag loss of the bearing. The loss from bending the belt over the pulley some consider a belt related friction loss.

Then you have the belt related losses:

1. Type of rubber compound and its viscoelastic properties during operation

2. Thickness of belt cover in contact with the idler roll

3. Idler roll diameter

4. Idler spacing

5. Idler trough configuration that influences the pressure between belt and idler

6. Belt construction bending stiffness

7. Steel cord or fabric tensile construction

8. Material loading crossection - determining the pressure distribution against the idler roll

9. Vertical and horizontal curve pressures between belt and idler

10. Belt tension and sag

11. Belt speed

12. Belt temperature

13. Steel cord diameter and pitch within belt construction

14. Then their are the pipe belt construction properties

I doubt I have noted all.

And after all of this, remember that the accuracy of your answer can only ever be as accurate as your least accurate input.

Don't get stressed in trying to refine the accuracy of your answer when you have broad assumptions or "standard factors" or "typical values" that can have wide variation depending on circumstances. ■

Hi Saviz

To answer your question, use a constant coefficient of friction between the belt and the pulley. I normally use 0.35 for most applications.

Then apply the following:

T2= Te x Start Factor x wrap factor (based on angle of wrap and 0.35)

For fluid couplings use Start Factor = 1.4

For VSD use Start Factor = 1.1 to 1.15

For direct coupled use Start Factor = 1.8 to 2.0

Cheers

LSL Tekpro ■