Hello Mike,

In general, the impact bed level is lower by about 12 to 25 mm, compared to adjacent idlers level. However, this will depend upon considerations such as :

1) Belt tension

2) Magnitude of impact force / energy

3) Belt particulars.

4) Skirt board sealing considerations

I suggest you to contact the manufacturers of such items, who will have more specific information based on their experience.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Mike:

The slider bed is slightly lower than adjacent impact idler rolls to minimize slding wear, heat and unnecessary drag. The slider bed offers a more solid foundation when large rock impact the belt beyond the contemplated deflection. The contemplated delfection is a selected value bases on the anticipated large rock impact that will:

1) damage the belt from lateral tearing especially in the splice of steel cord belts where the belt is not supported between rolls.

2) cause excessive damage to impact rolls from large rock

What should the idler distance be when using the slider bed?

You must know:

1) belt tension that lifts belt off slider bed from between impact rolls when the belt is loaded but has no impact force.

2. belt stiffness in 3 dimensions that resists delfection -- not so easy to obtain -- need experimental measure of stiffnes of belt or have already have finite element parameters that yield deflection with and without impact.

3) economic trade-off to select ideal spacing, idler troughing shape and impact idler design

4) poor or improved chute design that may produce high or low resultant impact force and may require or negate need for slider bed.

I am sure others will offer added clarity.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Dear Mike:

The slider bed is slightly lower than adjacent impact idler rolls to minimize slding wear, heat and unnecessary drag. The slider bed offers a more solid foundation when large rock impact the belt beyond the contemplated deflection. The contemplated delfection is a selected value bases on the anticipated large rock impact that will:

1) damage the belt from lateral tearing especially in the splice of steel cord belts where the belt is not supported between rolls.

2) cause excessive damage to impact rolls from large rock

What should the idler distance be when using the slider bed?

You must know:

1) belt tension that lifts belt off slider bed from between impact rolls when the belt is loaded but has no impact force.

2. belt stiffness in 3 dimensions that resists delfection -- not so easy to obtain -- need experimental measure of stiffnes of belt or have already have finite element parameters that yield deflection with and without impact.

3) economic trade-off to select ideal spacing, idler troughing shape and impact idler design

4) poor or improved chute design that may produce high or low resultant impact force and may require or negate need for slider bed.

I am sure others will offer added clarity.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Dear Mike,

Earlier respondents have already given certain information. I add following :

1) Impact bed length should be minimum.

2) Its length can be approximately feed chute opening plus about 300 mm on each side (depends upon belt width).

3) Impact bed is at lower level compared to adjacent idlers.

4) The distance between the idlers on each side of impact bed, will have more pitch. So, these idlers will get more load and the same should be suitable for the extra load.

5) One consideration could be to select the level of impact bed such that belt remains slightly above the impact bed, under normal weight of material and belt.

6) Impact force by the lump and the flow will push the belt on impact bed.

7) Clearance between belt and bed, should be selected such that the impact energy absorption is maximum as a consequence of belt deflection and strain (deformation) in the impact bed.

Referring to your question, thus clearance reduces belt wear on the bottom side, and also increases the capability of the system to absorb the impact energy. The energy absorption capability will be less if the bed is at the level of idlers. The decision for magnitude of clearance is subjective to other considerations also.

The distance kept between impact bed and idler minimizes forceful bending / wrapping of belt around idler. Thus, it minimizes the damage to the belt due to idler, as referred by you.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■