Originally Posted by sganesh

Dear Experts,

In many conveyors, at the inclined galleries, during idle running,

the belt is not touching the carrying rollers.

When the conveyor is starting, significant length at this location is

flapping up and down. When the material is started,

slowly the conveyor starts landing on the carrying rollers.

Is it accepted practice? How the structure profile ( angle of inclination)

is designed? Considering with material or without material ?

Also it causes spillage , when there is very low tonnage (TPH)

on the belt and also at the trailing end of the material passage on the belt.

I think that if the galleries ( inclination ) are designed considering the belt

is not having material , such problems may be avoided.

Request to post your valuable comments.

Thanks & regards,

Namaskar,

When a conveyor belt on an incline exiting a gallery like a surge bin it usually depends

on a mechanical counterweight basket tensioning a bottom smooth pulley on a vertical

track under the belt flight.

If the belt was not under tension the belt could not carry ore.

The counterweight basket permits the drive units lagged or unlagged drive pulleys to

create traction to rotate the belt and carry away the ore.

Spillage only occurs from a bad belt splice, broken belt splice, broken idlers, loose idlers

affecting the belt tracking and or fines build in the tail pulley creating such drag that the

belt is overloaded and stops and it occrs usually affecting the operation of a belt at at a

transfer point usually. ■

From what you are discribing it sounds as if the conveyor enters the gallery at a differnt angle than the angle in the gallery. The lifting occurs because the designer did not allow enough verticle curve between the working points of the intersection of the frame at the change in angle. The radius of this curve needs to be calculated to prevent the belt from lifting off the idlers even when unloaded.

You need to look at the two points of where the belt lifts off the idlers and look into the possibilty of shimming the idlers to properly support the belt in the area between those two points.

A picture of the conveyor at this area would give us a much better understanding of your system. ■

Mr. Sganesh,

There are three reasons that I can think of for loss of belt contact with the idler rolls when running empty. Mr. Blenkhorn has already mentioned one which is well known and I will list it first:

1. Tension uplift due to insufficient uplift radius

2. The belt is not troughable (tranverse bending stiffness causes it to span between the wing rolls and there is minimal contact on the wing rolls)

3. Failure to define the pelt profile along the neutral axis belt line. This is relevant at the ends where the belts transition from flat to troughed, at the tail, then troughed to flat at the head

The second reason, lack of troughability is also common, unfortunately, and the error is partly encouraged by belt manufacturers who list troughabitliy for different degrees of loading. The notion is absurd since the belt will have to run empty some time in which case belt alignment becomes unstable.

The third reason I have written about on this forum on several occasions yet goes largely unrecognized. Indeed CEMA publishes erroneous transition configurations, especially at the discharge, that guarantee belt uplift. The half-depth transition puts the top of the pulley above the neutral axis belt line which is less than one third of the trough depth from top of center roll. This is typically at the point of highest tension ensuring uplift.

Joe Dos santos ■