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An absolute test of vertical alignment is to vary the belt tension andobserve the system zero. A PERFECT ALIGNMENT WILL RESULT IN NO

APPRECIABLE CHANGE IN THE ZERO POINT.

SOURCES OF SYSTEMATIC ERRORS

Concave or convex curves near the weigh frame will cause belt lift or pulldown which will vary with load and belt tension.

Installation too close to a feed point will have the material settling as ittransits the weightometer and causing errors due to material movement inthe vertical plane.

Steering/tracking idlers within sometimes considerable distances (up to 20frames) can cause substantial error. They must be located a minimum of 11idler spaces either side of the scale-mounted idlers.

Installation near the head end of a simple inclined conveyor will producemuch less accurate results than those nearer the tail end.

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SSCCAALLEESS// WWEEIIGGHHEERRSS

1. BELT TENSION: The scale must be installed in an area where the belttension and tensioning variations are minimal. For this reason, the scaleshould be installed near the tail section of the conveyor, but far enoughforward so as not to be influenced by the infeed skirt boards and vertical

component caused by feed segregation in the vertical plane.2. BELT LOADING: It is desired that the belt loading be as uniform as

possible.3. LOADING POINTS: On high accuracy installations, the conveyor should be

loaded at one and the same point.4. MATERIAL SLIPPAGE: Product speed must equal belt speed at the scale.

The conveyor speed and slope should not exceed that at which materialslippage occurs.

5. CONVEX CURVES: Straight conveyors are preferred to curved conveyors.Corves are not recommended between loading point and the scale.Convex curves are permissible at a distance of 7 metres, or a minimum of

5 idler spaces, beyond the scale area idlers.6. CONCAVE CURVES: The point of tangency on a concave curve must be at

least 13 metres beyond the scale. The scale must be installed on astraight line and the belt must be in contact with 8 idlers either side of thescale.

7. WIND LOADING: To minimise the effect of wind loading, a minimum of 7metres must be enclosed on either side of the scale.

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