Reduce the idler pitch at the tail end.

It might not be sophisticated but it will be cheaper; involve less downtime and no extra supportive steelwork. ■

Originally Posted by Greenfeilds

Transient belt tensions during e stop for overland conveyor

Hi,

My question relates to an overland conveyor 2.5km long and is virtually flat. The drive is located on the return side near the head and the take up is a GTU also near the head.

During an e stop the belt sags significantly toward the tail end which can result in material spillage. Only after about 6 seconds, when the tension is able to redistribute at the tail does the belt sag reduce back to acceptable levels.

From my understanding this is due to the stopping time being too quick, which may be helped by increasing the system inertia with a fly wheel for example. Are there any other potential solutions to this problem that may be a cheaper and easier fix than having to fit a fly wheel?

Thanks for your assistance.

Originally Posted by johngateley

Reduce the idler pitch at the tail end.

It might not be sophisticated but it will be cheaper; involve less downtime and no extra supportive steelwork.

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You can handle this two ways:

Use Johns excellent suggestion OR

simply add a few more idlers to support the belt near the tail pulley.

Has anyone taken the time to use a theodolite or a simple six foot level to check the side to side level-(zero degrees) of this steel supported belt at this transfer point?

If you have continuos spillage like this its an automatic tattle tale to overloaded belts as

any belt that is properly loaded in IN THE CENTER OF THE TROUGH should not spill EVER!

The other thing is the belt timers; if they are not set correctly to permit the last belt to run

for a bit more time to avoid burying the tail pulley or having spillage it isa huge issue.

If the first belt is set to shut down ten seconds before the second flight and the second flight is set to shut down ten seconds later leaving the third flight to shut down at the thirty second mark leaving a clear belt with 10 or 12 belt stands with no ore on the belt ■

Originally Posted by Greenfeilds

Thanks for the suggestions so far.

We are looking into the possibility of increasing the stopping time of the conveyor to avoid this problem. This may be achiavle via control of the drive. We have bins inbye and outbye so run on with respect to other conveyors is not an issue.

At present, the belt is simply switched off and allowed to coast down rapidly. Most of the belt is pulled out of the loop and the counterweight raised high in the GTU. The current take up tension is sufficient to prevent slip and maintain acceptable sag during running and accelerating conditions, however during a coast down stop the sag is enough to spill material off the belt at several locations within a few hundred meters of the tail. We would need to add many new idler sets to cover this area.

My thoughts are that increasing the take up mass will not provide entirely fix this problem as it involves transient tension redistribution around the conveyor. If the take up mass was increased, less belt would be pulled from the loop however sag would still exist at the tail to some degree until tension redistributes and the loop pulls back in.

In the event of power outage the rapid coast down stop will be unavoidable, however this is not common and may be tolerable in these instances.

Can any experts comment on their experiences with controlling tension during stopping on flat overland conveyors of reasonable length, head driven, head take up? Thank you.

Part of me is asking why you are spilling?,

and when the last time was you cut belt out

due to stretching and worn belt?, AND if you

are spilling your idler count is too, too, low

even when the belt is stopped?

It should not spill period unless the belt breaks,

OR if it is overloaded and spills across the trough fom overload.

IF not your belt is too thin. How many layers comprise

the thickness of the belting you have?

Are you using mechanical splices or vulcanised splices for this belt????????

What is your idler spacing between each conveyor stand?

I think that is most of your problem as the belt AND the idlers

are not supporting the weight loaded across the trough apparently.

Help us to help us help you ■

I appreciate this does not really assist, though it sounds like an assessment by a competent engineer is required.

This "sounds" like a new installation - maybe the original designer would be interested (or even liable..).

Regards,

Lyle ■

....."At present, the belt is simply switched off and allowed to coast down rapidly. .......

.......In the event of power outage the rapid coast down stop will be unavoidable, however this is not common and may be tolerable in these instances."

According to the quoted text the rapid stopping is going to be unavoidable and tolerable. Therefore I see no cause for your concerns.

If you pay more attention to the inbye feed you might reduce burden flow onto the belt and this will go some way to reduce the amount of spillage.

Presumably the plant is in operation for some time; commissioned and taken over. Designer liability is out of the frame.

'Much Ado About Nothing.' ■