Mr.Davis,

The answer to your question is dependent on the ability to analyze the pressure and indention the rubber undergoes at the idler roll contact with the belt. See our website for a visual:

http://www.conveyor-dynamics.com/about/power.htm

There are times when the dual center roll has some effect. This usually occurs with higher tonnage and wide idler spacing.

As the prior responder referenced, the Henderson Mine has larger center rolls which also gives a benefit.

These points are factored when the rubbers rheological properties, and viscoelastic modeling is performed on the belt/idler interface.

Here at CDI, we can analyze the differences from first principles.

Lawrence Nordell

Conveyor Dynamics, Inc. ■

This idea I think was originally developed by Stepson and Adamson or something, ne way - Svedala took them over which in turn has been taken over to become Metso. I have a *pdf which I can e-mail you into the research of these items.

However my confidence with these working in arduous conditions is doubtful, the swivel units are prone to problems with build up of material.

The concept I think is by eliminating "Idler offset" it tries to ensure the idler load is spread across all the toughing sets.

The more components etc - four idlers and swivel units mean the cost is increased to begin with.

The way forward is to improve affiance - I am yet to see any on site.

e-mail: stuart.davies@virgin.net ■

Stuart,

Could you elaborate on this pivot arragement for dual center trough rollers?

The Metso dual center roll I have seen does not pivot.

The dual center roll benefit comes from the reduction of roll/ belt interface pressure. The reduction in pressure drops the power.

Bothe dual roll and larger diameter rolls reduce the pressure. The formulation has already been published by many authors in Bulk Solid Handling myself included.

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Yes I agree with above statement. The pivot feature I was talking about is as follows. The frame holding the two center rollers is known as the pivot frame and is allowed the rotate vertically. This compensates for any vertical misalignment between adjacent rollers ensuring an equal spread of load. ■