When the idler spacing distance is increased, motor may take higher power. So energy cost will go high.

Regards, ■

Dear experts,

Have you seen the carrying belt is supported by water tray ? No tollers ; No frames .

Project & energy cost will be much reduced.

I have not seen , only heard it.

Regards, ■

The answer is very complex. Usually, the spacing is selected, based on economic capital and operating factors with the following criteria:

1. Load on each roller

2. Bearing selection

3. Power penalty

4. Idler junction stress and deformation

5. Belt bottom cover thickness - controlling stress at roller contact to not abrade the cover

6. Roller diameter

7. Trough angle

8. Vibration control

9. Belt tracking control

10. Belt construction type and stiffness

I am sure some points are missing that do not immediately come to mind.

I am aware of the 6 m spacing on Selby (UK) 12 km incline for both carry and return that operated at 8.5 m/s speed, transporting 2500 t/h coal with 193 mm diameter rollers, by memory, balanced for speed.

1 m spacing is used on very high tonnages. Using on low tonnage is a waste of money. ■

Use of 1 m spacing might support 8,000 - 10,000 t/h ■

Each Idler has a CEMA load rating or you can design your own idler from basics by choosing the shafts, bearings, rolls then sizing the frame according to the rating. The idler spacing generally depends on the idler's basic load rating (for the load to be carried) and the desired operating hours, say 60,000 hours typically. If the load rating allows for a wide spacing then we must consider the affects on the conveyors travel resistance. This may dictate a higher tension basis in order to control sag to lesser values than the typical 2% or 1.5% and may also dictate larger diameter rolls. On the other hand, so as not to raise the tension basis solely for this purpose we may choose the longer idler spacings only at parts of the conveyor where the tension is naturally high, typically quite beyond the tail loading area.

Joe Dos Santos ■