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When the idler is not perfectly aligned with the belt additional loading on the idler and additional drag on the belt can be introduced.

Alignment Effect on Idler Load

When an idler is higher than the adjacent idlers, the belt tension will add load to that idler. This load can be estimated and used in the idler selection procedure.

•Vertical Misalignment is the vertical height difference between idlers as described in the CEMA manual. This value is input on the idler tab spreadsheet.

•The Calculated Idler Load, as shown on the Idler Tab spreadsheet, is the idler loading including material, belt and the tension affect due to idler misalignment.

•The estimated L10 Life of the idler considers this Calculated Idler Load.

The "Vertical Misalignment" is only used for the idler selection process, it does not contribute any drag to the overall conveyor calculations.

Alignment Effect on Drag (CEMA 7th Edition friction calculation)

Idler misalignment from the direction of belt travel can also cause traverse slip between the idler and the belt, addition drag to the system. The CEMA 7th Edition friction calculation estimates this drag and includes it in the overall tension and power calculations. The following values are input on the Idler Tab spreadsheet

•Angular Installation Tolerance is the expected average installation deviation referenced from the center roll to perpendicular to belt travel.
 

•Manufacturing Tolerance is the effective misalignment due to manufacturing variation.

•Forward Tilt is the intentional inclination of the idler frame or wing roll to aid in belt tracking.

•The Idler to Belt Friction Factor is for sliding between the belt cover and idler material.