Conveyor Use In Monsoon
Originally Posted by deepakvermaa
during monsoon, there is a common problem of rollback of wet coal/slurry in the inclined portion of belts.
Since, the wet coal/slurry is unable to climb the degree provided in the belt there is rollback of material which after reaching the end of inclination spills on both sides.
What are the ways to prevent this rollback/Spillage?
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The best way to stop this problem is to install plastic conveyor covers and
roofs over the transfer points.
The properly sized conveyor cover will also have a pair of holes in order
to grease the idlers without removing the covers. ■
Avalanche
Originally Posted by deepakvermaaduring monsoon, there is a common problem of rollback of wet coal/slurry in the inclined portion of belts.
Since, the wet coal/slurry is unable to climb the degree provided in the belt there is rollback of material which after reaching the end of inclination spills on both sides.
What are the ways to prevent this rollback/Spillage?
The vogue expression for your situation is 'Avalanche' which is pretty self explanatory. It amazes me how often the phenomenon is ignored at the design stage. If rainfall forecasts are ignored or not specified that is something you cannot change.One can simply quote the design error and go from there with a high level of impunity. On a belt carrying 3000tph along a path of 900m at 3m/s the coal is exposed to the rain for 5 minutes whereas it is subjected for about 6 weeks to identical rainfall in the stockyard.
There will be initial dispersal of the pond on start up as the newly introduced coal ploughs the stagnant pond along the troughed belt. This is bad enough, but survivable. Water, being heavier than coal, will soon percolate down to the belt surface and develop a boundary condition which lubricates the belt and coal interface. This develops a potential slip plane which is also subject to the belt inclination. If the belt is loaded correctly: ie wet coal has been recognised, then the coal content should be considerably less than during dry running. Of course this never happens and there is a much larger burden cross section than was ever considered in design.
How much water can your bunkers drain off? I realise your problem is getting to the bunkers in the first place. None of the correct solutions are cheap.
A: Introducing dewatering screens just before the vertical curve would be best but you would need several screens with complex feeding and this would shorten the effective reclaimable length. You would have to leave that end of the pile for drier times or discard it altogether.
B: Even if you just reduce the throughput to correct loading levels the boundary layer/slip plane might still occur. You have to get rid of some water before the vertical curve. The cheapest way might be to reduce the wing idlers for a short distance until some water runs out over the belt edges. Some skirting will be necessary and that should have a reasonable gap for water egress. Then you resume the original troughing and take it up over the brow curve. The reduction in reclaimer access will be less than A; you will have spent less in an attempt to reduce water content. If it doesn't work....at least you've controlled the spillage.
Good luck. ■
John Gateley johngateley@hotmail.com www.the-credible-bulk.com
Thanks A Lot!
Originally Posted by johngateleyThere will be initial dispersal of the pond on start up as the newly introduced coal ploughs the stagnant pond along the troughed belt. This is bad enough, but survivable. Water, being heavier than coal, will soon percolate down to the belt surface and develop a boundary condition which lubricates the belt and coal interface. This develops a potential slip plane which is also subject to the belt inclination. If the belt is loaded correctly: ie wet coal has been recognised, then the coal content should be considerably less than during dry running. Of course this never happens and there is a much larger burden cross section than was ever considered in design.
How much water can your bunkers drain off? I realise your problem is getting to the bunkers in the first place. None of the correct solutions are cheap.
A: Introducing dewatering screens just before the vertical curve would be best but you would need several screens with complex feeding and this would shorten the effective reclaimable length. You would have to leave that end of the pile for drier times or discard it altogether.
B: Even if you just reduce the throughput to correct loading levels the boundary layer/slip plane might still occur. You have to get rid of some water before the vertical curve. The cheapest way might be to reduce the wing idlers for a short distance until some water runs out over the belt edges. Some skirting will be necessary and that should have a reasonable gap for water egress. Then you resume the original troughing and take it up over the brow curve. The reduction in reclaimer access will be less than A; you will have spent less in an attempt to reduce water content. If it doesn't work....at least you've controlled the spillage.
Good luck.
Respected Sir,
Thanks a lot for your valuable inputs regarding options to eliminate Rollback problem in belt conveyors.
I suppose option B is easier & cheaper to implement as far as our system is concerned. Will definitely execute this option and share the experience. ■
Rollback Problem During Monsoon
Respected Seniors,
during monsoon, there is a common problem of rollback of wet coal/slurry in the inclined portion of belts.
Since, the wet coal/slurry is unable to climb the degree provided in the belt there is rollback of material which after reaching the end of inclination spills on both sides.
What are the ways to prevent this rollback/Spillage? ■