Dear Graham,

We have such knowledge to handle clay and rock in one chute. There are caveats to this claim. Tonnage, belt speed, and work orientation.

In principle, the belt work points cannot deviate as they might otherwise with high speed belts. That is they must be a controlled distance and somewhat close to the discharge pulley centerline.

We would appreciate the opportinity to be of service. ■

http://en.wikipedia.org/wiki/Caveat ■

Gentler version via Google:

an explanation to prevent misinterpretation c: a modifying or cautionary detail to be considered when evaluating, interpreting, or doing something ■

Would like to help. Tell me more, like the general geometry of the transfer planned such as:

1. height between work points

2. plan view orientation between discharge and receiving conveyor

3. belt slopes

4. discharge pulley diameter

5. Transition idler configuration from discharge conveyor ■

Your description may have merit. However, if we can show a significant reduction in belt wear and the potential to puncturing to your proposal, will it be of interest?

Do you mean a "curved hood" when you describe a "spoon type baffle" to describe the discharge flow trajectory?

If I assume so, then when large rock are discharged, with little clay or cohesive material, with a curved hood, the rock's kinetic energy may be approximately equal to discharge conveyor velocity plus drop height's gravity acceleration velocity.

Given an appropriate hood geometry, when all clay like material is redirected, will the cohesive strength cut the discharge velocity to zero and allow material to buildup, eventually leading to blockage? If so, then your idea may not be so good.

The nature of highly cohesive materials is to gain strength with impact or shear due to the internal consolidation of the fine grain. So will the internal strength or wall friction allow continuous flow? Then there is prayer that the material mix will have sufficient rock to scour the hood build-up. The build up can happen quickly or by degrees from the edges that build toward the chute hood center.

Now there is another way that guarantees flow. Last chance to dance.

DEM can demostrate the hypothesis of all scenarios and indicate the difference in propensity to wear or punture the receiving belt. ■

At our cement plant, we do both mix/mix plus rock/clay separatet - depends on plant process locations...ie before mixing and after.

We have found that

Shallow impact angle with steel liners (HARDOX type) is best.

Chute performance wrt blockages and wear rate is a compromise

We have used rubber curtains on top of the steel liners - clay builds up and then breaks off > high wear rate.

Best to try and avoid clay builds up > these will become large > crack and fall off when 100% dry and this can be a bigger issue.

We have toyed with the idea of ceramic inserts into rubber mats....eg end of stacker boom conveyor.

Do not turn the material too much ie we have a trouser leg chute for a 90deg. transfer...both legs were then angles in the same direction as the belt > the double angle chute tended to block up until we killed off the forward incline

The best sit. is direct loading onto the second belt > no contact so no buildup.

Our rates are up to 2000tph - 3.3m/sec 1800mm belt.

Our worst sit. is a travelling stacker > hence, different apparent speeds with a curved chute > has to be curved to OEM geometry.........we find that the safety pull rope switch acts as a secondary blocked chute switch.

If you are interested, we can send you some photos.

Thanks

James ■

Hi Graham,

The problem you have is trying to balance liner wear against the chute blocking. Our experience is you must first get the design right for the clay material as chute blocking during production is a major hassle. With sticky material the key is not to slow the material down anywhere within the transfer and this requires;

> Very shallow angles at which the ore is intercepted both at the top and bottom of the chute if you are using a hood and spoon type chute.

> Careful design of all the deflectors such that you do not create a pressure zone in the deflector through insufficient cross sectional area. This create a material boil which will propogate build up and eventually a blockage

> There can be no impact point within the chute

Once you have this designed your problem is wear on the liners with rock as material speed has a an effect to the power of 4 on substrate wear with abrasive materials and designing for sticky materials invariably means the speed through the transfer is a lot higher. Optimally trying to create ore on ore flow is the best solution but this is very dependent on the material type, size distribution etc. In your case it is likely to be impossible given it is overburden. We are dealing with these issues quite frequently and it is always a compromise between optimal chute life and performance while operating.

Regards

Col Benjamin



Gulf Conveyor Systems Pty Ltd ■

I agree with Colin.

Also, if you have a mix mix of rocks/clay, then there will be different paths inside the chutes and hence, onto the next belt and this may or may not be an issue downstream eg all rocks on one side etc.

We try to avoid creating buildup eg in corners etc > as these become very hard lumps that can and do cause issues downstreams eg bin outlets, weighing equipment.

Another issue with clay is when it is very very wet > best to stop operating is usually best here unless you go and cover all of your materials handling equipment/ storage yards. That is a risk, cost benefit decisions

Cheers

James ■

Graham

Try Uni-Chute

Contact: Jeff Mathlin

Company: CVR Crushing Equipment

Phone: +61 8 9370 2267

Fax: +61 8 9371 6607

Email: cvr@iinet.net.au ■

The effect of clay and a high belt speed can result in some very peculiar problems particularly if its loading onto an inclined conveyor.

It is highly likely that at some stage you will experience the phenomenon of roll back where the clay creates a huge Swiss roll on the receiving belt which can be as high as 1.5m. This lump depending on its consistency will either carry to the next transfer point or slump over the sides tripping the pull cord.

The belt speed that you describe should allow you to design your chute that under most circumstances will not block. I can help in this regard either designing or supplying the chutes. ■

Dear sirs,

I am new to this forum and amazed at the straightforwardness, solid knowledge and good cooperation, especially from Colin Benjamin.

Graham, did your project come forward? I am facing similar situations here in Chile. I am very intrigued at how your project alternatives have progressed and might be able to add some suggestions of my own.

Regards

Joerg ■

Originally Posted by Graham Spriggs

Hi everyone..

We are designing a round-the pit conveying system to handle overburden from an open cast coal mine.

Most of the overburden is abrasive rock, but nearly 30% of it is clay which can be extremely sticky when wet.

Has anyone had any success with chutes that can one day handle rock and another handle clay?

We will need up to eight conveyors in series, and I fear that the availability will end up being impractically lowdue to blockages/excessive wear.

Regards

LSL Tekpro

=========================================================

Hello Mr. Sprigs,

there are several manufactures of poly liner material here in the states that

manufacture poly liner material in several thicknesses, widths, and continous rolls

that are used to line truck bodies etc that are used carry waste rock,

construction debris, clay filled ditching dirt's sugar beets, potatoes.

These poly liner materials are cut to size and bolted to the surface of the dump

body to allow the quick dumping of the product whether is is dirt or potatoes,

sugar beets and other sticky muck etc.

I do not represent these folks etc., but would be glad to send you their collective

contact information for your use.

lzaharis ■

Try uni-chute

Contact: Jeff Mathlin

Company: CVR Crushing Equipment

http://www.cvrcrushingequipment.com.au

Regards

Ziggy ■

Graham

Ring Jeff and ask him about Uni-Chutes

Contact: Jeff Mathlin

Company: CVR Crushing Equipment

Phone: +61 8 9370 2267

Fax: +61 8 9371 6607

Email: cvr@iinet.net.au

Regards

Ziggy Gregory ■