Main concern:

95% of problems we see with screens general rule of thumb in the field is....FEED TO....NAMELY incorrect feed.

Feed material must be sent to vib screen the full width of the screen, in a proper drop height, not too high, in a human manner...so Mr screen can deal with it.

a bulk feed to a vib screen ...kinda just dumping on it would not be desirable at all.

George Baker

Moderator

Originally Posted by mohandes

Is there any problem if using screen under the bin?

If we use blind surface in the area under the bin, one equipment can be both feeder and screen.

I have seen grizzly feeders, but is there any case which screen experienced under the bin?

■

Mohandes, I realised the benefits of your proposal back in 1994. I've never been able to put it into operation but the younger generation generally agree with you and me. Go for it. Save the headroom, save the complexity, provide faster control. You've got the full width feed if you play your cards right and that means you can reduce the bed depth in the plate to nearly the screen depth. Will it start under load? Why not....a normal vibro-feeder has a much smaller vibro-motor.

What are you waiting for lad...and thanks for bringing back memories. I talked to Lockers, Warrington UK, about the possibility. They said it was already done....but I doubt they understood the concept. ■

Gents

Vibrating screen is a screen not a feeder. To install it under the bin you need blank area to controll the flow from the bin - effectivelly creating part feeder part screen. Agree with George that 95% of problems are installation/feed arrangement related, I have seen few screens installed correctly with making kind of a hybryd it will get worse - but only by remaining 5%.

Regards

Ziggy Gregory

www.vibfem.com.au ■

Originally Posted by mohandes

Is there any problem if using screen under the bin?

If we use blind surface in the area under the bin, one equipment can be both feeder and screen.

I have seen grizzly feeders, but is there any case which screen experienced under the bin?

Solution will depend on properly defining the problem.

What is the material in the bin? Do you have physical specs - size analysis, (size at which separation is desired?), bulk density, moisture, angle of repose etc.

What is the size of bin? A drawing will help.

What is the headroom available under the bin?

What is the desired material discharge rate from the bin? ■

The concept under scrutiny suggests that:

bin outlet is 'chisel' so that there is a material bed available to the full width of the screen deck;

drop height is practically non-existent because the prudent bin designer has limited the download and that limiter obstructs the empty bin drop height. Such is normal to protect a feeder when appropriate;

extra burden download over the feeder plate is easily handled by the upstream supports in both the open and shut situations;

the principle can be applied "across the board" Ho. Ho. Ho...

(Regardless of meaningless salesman concerns over material in the bin, size of bin, available headroom etc etc. If it won't come down out of the bin then the bin designer has wasted all our time Catch the Drift?) ■

Isn't there a limiting head height that the screen is able to start under? Is the necessary screen motor torque, to get initial cyclic motion, to complete first starting action the practical/commercial limit?

This comes before blinding the section under the bin. Certainly bin bottom configuration is important. Maybe a step shelf, like an ore pass will control the pressure on the blind section.

We can model this action. I suspect the torque is wed to the active bed depth and wall friction in addition to the lifting action along the sloped vibrating screen bed.

ROCKY DEM can solve this with any configuration of bin bottom, screen and blind surface.

An example of a vibrating screen: http://www.conveyor-dynamics.com/Exa...youtubev6.html

No problem to place any bin above the blind screen deck together with the single or multiple screen and orbit of choice and wa-la. ■

Originally Posted by nordell

Isn't there a limiting head height that the screen is able to start under? Is the necessary screen motor torque, to get initial cyclic motion, to complete first starting action the practical/commercial limit?

This comes before blinding the section under the bin. Certainly bin bottom configuration is important. Maybe a step shelf, like an ore pass will control the pressure on the blind section.

We can model this action. I suspect the torque is wed to the active bed depth and wall friction in addition to the lifting action along the sloped vibrating screen bed.

ROCKY DEM can solve this with any configuration of bin bottom, screen and blind surface.

An example of a vibrating screen: http://www.conveyor-dynamics.com/Exa...youtubev6.html

No problem to place any bin above the blind screen deck together with the single or multiple screen and orbit of choice and wa-la.

I recognised this thread as ideally suited to DEM resolution while I was shaving this morning. It needs a younger person to follow it through so that it doesn't lie on the shelf like it did in my case. I'm sure there are many who would like to see the idea bear fruit....and some who wouldn't.

My particular application would have been to reduce headroom requirement in a circular reclaim situation where it had been decided to screen finer material onto the take out conveyor before dumping the large rocks on top. The client's proposal made for a very congested maintenance operation. ■

Hi there,

I would not want this without at least a device to control the flow.

And I agree with one of the writers: some more details about the application would sure help for a better understanding. ■

Originally Posted by Rotex Europe

Hi there,

I would not want this without at least a device to control the flow.

And I agree with one of the writers: some more details about the application would sure help for a better understanding.

This is a flow control device...that's the point of the upstream apron. ■

Originally Posted by louispanjang

This is a flow control device...that's the point of the upstream apron.

I realise that. But can you imagine what will happen if this is a very free flowing product. We use a small feeder under a small hopper under laboratory conditions and this sometimes causes troubles already because the product keeps flowing, even with the feeder not running........

That is why some more application details would be helpfull. ■

If a material is so free flowing it does not need a vibro feeder in the first place. ■

Hello Mohandes,

We generally do not come across combination of feeder and screen, as single item. Possibly it may be resulting into inefficient feeder as well as screen, for following reasons:

1) Feeder pan width has relation to hopper outlet size.

2) Screen deck width depends upon capacity mtph and screen out size. Material spread on full width is very important for efficient screen-out.

3) Differing requirement of vibration force, vibration amplitude and frequency, for feeder portion and screen portion. Adjustment for suitable frequency or amplitude for one part, may become less efficient situation for other part.

4) Equipment may be becoming too big and uneconomical.

Equipment called grizzly feeder or grizzly screen, I think dominantly works as feeder and screening function is secondary in nature. This equipment utilises the concept you have mentioned. You may look into market for availability of equipment of similar type which ideally is substitution of efficient feeder and efficient screen you are contemplating.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

When you say grizzly you are talking screen.

Other replies in bold

1) Feeder pan width has relation to hopper outlet size. This always the case. Use a chisel outlet for the hopper.

2) Screen deck width depends upon capacity mtph and screen out size. Material spread on full width is very important for efficient screen-out. Same as 1)

3) Differing requirement of vibration force, vibration amplitude and frequency, for feeder portion and screen portion. Adjustment for suitable frequency or amplitude for one part, may become less efficient situation for other part. Operations are sequential. If the screen can handle the capacity the only variance is the slope for the feeder. 4) Equipment may be becoming too big and uneconomical. ??This will replace a vibro drive and reduce headroom. The concept came about because it was too big before. ■

Originally Posted by louispanjang

When you say grizzly you are talking screen.

Other replies in bold

1) Feeder pan width has relation to hopper outlet size. This always the case. Use a chisel outlet for the hopper.

2) Screen deck width depends upon capacity mtph and screen out size. Material spread on full width is very important for efficient screen-out. Same as 1)

3) Differing requirement of vibration force, vibration amplitude and frequency, for feeder portion and screen portion. Adjustment for suitable frequency or amplitude for one part, may become less efficient situation for other part. Operations are sequential. If the screen can handle the capacity the only variance is the slope for the feeder. 4) Equipment may be becoming too big and uneconomical. ??This will replace a vibro drive and reduce headroom. The concept came about because it was too big before.

The best option is a pan feeder under the hopper feeding directly a vibrating screen. The advantages of this are that the feeder will be designed and take the load of the material in the hopper and the screen will screen out the material and have a nice spread feed from the feeder. This option will also not create any extra height. We have done this many times before. ■

Originally Posted by Svenson82

The best option is a pan feeder under the hopper feeding directly a vibrating screen. The advantages of this are that the feeder will be designed and take the load of the material in the hopper and the screen will screen out the material and have a nice spread feed from the feeder. This option will also not create any extra height. We have done this many times before.

Everyone similarly involved has 'done this many times before'.

"This option will also not create any extra height." So how do you accommodate the extra falling length, for starters?

It is quite obvious that this thread has fallen on deaf ears "None so deaf as those who don't want to hear."

Has one of the suggested devices ever been tested? ■

Originally Posted by mohandes

Is there any problem if using screen under the bin?

If we use blind surface in the area under the bin, one equipment can be both feeder and screen.

I have seen grizzly feeders, but is there any case which screen experienced under the bin?

I saw such a machine advertised in the Indonesian Mining Expo last Friday. Twice!

It seems that Chinese manufacturers sometimes behave like the bumble bee. That insect was supposed to be aerodynamically prevented from flight. Nobody bothered to tell the bee, so it just started flying anyway. An American story. ■