Dear Mr. Singh:

It depends on the application/design conditions. Here are some criterion:

1. Shear stress under cord must be lower than 14 kg/mm2 and is therefore dependent on steel cord diameter and pulley diameter which is a mfgrs rule

2. Set for belt life due to abrasive wear at carry side idler pressure interface with belt -- the last mm is needed to surround the cord for adequate splicing and so depends on the product, speed, pressure, trough shape and loading

3. Resist large rock impact energy and damage to belt cover under cords at load station

4. Sufficient to exceed minimum fatigue stress at idler junction so that life of belt will exceed warranty without axial failure between wing and center roll junction. THis is dependent on belt width, idler trough configuration, idler roll diameter, idler spacing and material loading

5. Sufficient so that belt will not buckle in belt turnover which is dependent on belt tension, turnover twist length, and stress limiting criterion

6. Allow proper troughability with given idler configuration

7. Depends on bottom cover belt physical properties and the application's environmental conditions

8. Depends on lump size to be transported together with belt sag factors and belt speed

I have seen seen covers as low as 3 mm. I would not recommend such.

Your silence is deafening. ■

After thought:

9. Depends whether belt rip protection is embedded in bottom cover -- which needs rubber cushion distance between cords and antenna as well as stated conditons above. ■