Dear sir

for chute design you can contact conveyor dynamics as per details given below

contact person -Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com

nordell@conveyor-dynamics.com

phone: USA 360-671-2200

fax: USA 360-671-8450

A R SINGH ■

Dear Gareth,

I thank Mr. AR Singh for the kind introduction. Conveyor Dynamics, Inc. may be of service. I hope you will take some time to become educated on Discrete Element Modeling (DEM) NOt all DEM methods are created equal such as:

1. Particle model size and speed of execution

2. Particle shape model can handle

3. Particle size range model can handle efficiently

4. Rheology of soils model can handle

5. Testing of flow characteristics and implementation into model

6. Multiple processor handling

7. Types of boundary conditions

8. Modeling needs for liner and belt wear indexing

9. Modeling need for degradation indexing ■

When using computer modeling for chute design I would also offer that expirience in chute design is of the utmost importance. Martin Engineeing has years of real world expirience in solving not only chute design problems, but numerous other conveyor problems as well. We can be contacted at 309-594-284 in the United States. ■

Matt,

Could you elaborate on your comment. I do understand you need to be a little vague or discrete in labeling a DEM product and that the products are undergoing revisions. Your comment suggests specific experience.

Like with rubber technology, not all DEM programs are either created with the same technical functionality or are static in their creation.

The codes provide varying services today and will improve with another day of analyses as has been elaborated upon in the forum. ■

Matt,

Could you define what criteria you require in a DEM code to purchase or lease? ■

I beleive that there is an academic (and comercial company) in the Uni of Nth Qld that has developed a commercial DEM model which has been used for things other than conveyor chutes eg demo and collapse of smoke stacks, bridges etc etc.

I can not remember his name.

But WBM - consulting engineers - Brisbane - Russ Morrison may be able to help U out with this.

What I understand of DEM - whihc is not that much - is that U need to understand and appreciate the model basis....I gather that U can model with simple balls, apply a stiction factor to the surface balls to simulate cohesiveness and some models can have the balls stuck together to simulate different particle shapes.

Then U also have different sizes (or diameters) to boot as well.

I do not know if anyone models elasticity of the balls.

All of the above are attempts to model the real material.

Perhaps some more learned scribes can elaborate on the modelling basis, techniques and pros and cons of the model basis.

Cheers

James ■

I understand your wishes. How will you determine that the model someone promotes does replicate real world conditions? If you are not knowledgable of the pitfalls, technical omissions, analytic errors, et al how do you accept one model over another.

If price is the motivation, you should make known what level of competence is required. Its like buying different computer chips some have more performance at a higher price.

I suggest you get help to understand what needs to be known. One step is to establish test procedures with known outcomes that you can apply with your model of interest. Then rank the results. I have helped with some queries. There are many. This process should be without modeller input. However, the modeller should be priveleged to the queries that will guide your judgement and make sure these features are included or claim to the contrary.

Some points of interest are: input routine, output routine, speed of execution, model size, model properties, graphics on input and output, characterizations such as damage to surfaces, damage to product, levels of physics such as solids and their shapes, elasticity, plasticity, ratio of smallest to largest particle groups, gas flow field, fluid flow field, animation range, ......

You quest must be fair to all interested parties. Ways of the past were to have a leading developer become the guide for all wanabees. Some spend the money on research while others are content to copy with no investment. Ths process is not fair. We for one, will not participate in such a game. Some can stand up with a straight face and say I can when they cannot. Those that can, do not wish to educate those that can not. This is only acceptable when the information comes into the public domain. ■

There are a number of organisations that have looked at DEM to evaluate transfer chute models. The first was the CSIRO, and the key person was Paul Cleary. In the early days I know Larry and Paul had quite a bit of contact.

In addition to Conveyor Dynamics there is Overland Conveyors in Denver Colarado and As James has noted, the organisation in Townsville in Australia that I also forget the name of but we did have some dialogue with them and they are very capable.

We also sponsored a PhD student at Wollongong University, so I know this institution is also doing work in this area.

The important issue re DEM is that it a methodology to evaluate designs, not a design tool per se. We use a completely different technology to develop our designs and then use DEM in some particular cases where we have concerns due to the complexity of the material flow. Also like all technologies, it works on making assumptions so the inputs are critical to getting good outcomes and generally this is best achieved by testing parameters against your model and then reverse engineering from the outcomes achieved.

Trust all this helps

Col Benjamin

Gulf Conveyor Systems ■

Dear James:

FYI the technology has advanced beyond modelling with simple ball shapes and clustering of balls to make asperity in the granular structure. Most DEM models are called soft contact models that use elasticity and some also plasticity.

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Colin,

The pecking order of chute mathematical modeling is to my knowledge:

1. 1963 Jerry Johannson (later of Jenike & Johannson) and Hendrick Colijn, US Steel high speed photo studies of curved chute granular flow followed by math slug flow modelling of same - good stuff

2. 1970's Prof. Peter Cundall develops True Ball 2-D DEM model and gives it to all interested parties - this code can do what J&J did with slug flow model.

3. 1980's Prof. A. Roberts - slug flow math model for chutes

4. 1994 CDI 3-D CFD model of chute flow for Palabora (published incl point 5 below)

5. 1994 Dr. A. Hustrulid DEM based on collaboration with CDI. Andrew later applied his model to chutes and went into business venture with Overland Conveyor. Andrew is now separate from Overland and promoting his own technology.

6. 1995 Itasca, Prof. Peter Cundall, had 3-D sphere model (3-D PFC particle flow model), but did not apply it to chutes

7. 1995 CDI 3-D non-spherical DEM model and beginning collaboration with CSIRO and Dr. Paul Cleary. Paul had not applied his model to chutes at the time.

8. Many others followed with derivatives. ■

Colin:

Maybe you do not use DEM methodology for chute design but others do. It is the only mathematical means to optimize chute shapes for flow behavior (free flowing and plugging), liner and belt wear, product degradation and dust generation prediction.

I am willing to have you show me wrong. ■

Dear All,

We are offering Chute Maven, a discrete element program specifically intended for transfer chutes, for sale. The program is easy to use:

1.Draw your geometry in 3D in Autocad.

2.Import geometry into the program.

3.Set belt speeds, material properties, and flow rate.

4.Run the simulation.

5.Look at the results and create animations.

6.Make changes to your design in Autocad.

Visit www.hustrulid.com for more information.

The first application of the DEM for transfer chutes, that I’m aware of, was done by myself with the assistance of Prof. Graham Mustoe, my thesis advisor, at Colorado School of Mines (CSM). We did a DEM analysis for 20 Mile Coal Mine in Colorado in conjunction with Continental Conveyor in the fall of 1994. While we were doing that project Mr. Nordell visited CSM as a guest lecturer in the mine plant design class and I shared with him some of our research and modeling. The following week we provided the figures included at the end of Mr. Nordell’s bulk solids handling paper on designing curved chutes using computational fluid mechanics (CFM). We had one or two conversations in the following couple of weeks but never reached an agreement on any collaboration.

Andrew & Ginger Hustrulid ■

Dear Andrew,

Since you have made an erroneous public statement concerning me without consulting me, I feel compelled to state the facts:

1. In Mid 1994, I was introduced to yourself by Mr. Mark Alspaugh, when I shared with him my vision on chute designs, having just successfully completed the Palabora curved chute project in April 1994.

2. CDI started the Palabora curved chute engineering in 1992 and completed it in 1993. This required: 6000 t/h, 15 degree incline transfer upgrade modeling, design, material specifications, and supporting Rio Tinto during their fabrication and commissioning.

3. Palabora was recognized to be successful almost immediately with visible benefits in gently placing large rocks on the belt, eliminated most spillage, and with measurements showing a 10 fold wear life increase. From the initial 1989 production date, the 18 mm top cover was destroyed in less than 3 years using a conventional rockbox loading method.

4. When I met you in 1994, you had no concept of applying DEM to transfer chutes. You were looking for applications. I outlined CDI's interest and offered to further support you to complete your Ph. D. when the Bureau of Mines shut down your funding.

MY DISPUTE OF YOUR FACTS

5. In mid 1994, during our discussions on a collabortion, Mark Alspaugh saw an opportunity to apply this concept for Cyprus Coal and approached you. I was a little taken back by your backdoor handling after I had made multiple visits to CSM on a collaboration. I requested that this be a one-of if you and CDI were to continue as we have discussed. I was misled.

6. My invited lecture, at CSM, ocurred sometime after we began our discussions. Dick Bailey, a CSM adjunct professor and Continental Conveyor Co. salesman, made the invitation.

7. In 1994, I invited you to display your knowledge on DEM in an article I presented for publication BSH Vol. 4 No. 4 Oct-Dec 1994 Titled: "Palabora Installs Curved Transfer Chute in Hard Rock to Minimize Belt Cover Wear". Work backward on the dates. I invited your work to be included at this time. You had No Chute Simulation to offer for publications at the time of my invitation to you (Reference pg. 743). These facts do not jibe with your story and timing. Maybe a little amnesia?

Personally, I could do without this non-professional airing. I dare not ask the need for this and see no reason for further response.

The only positive result from our meeting is that CDI developed a in-house DEM code coupled with gas and fluids, particle breakage, wear indexing and more to reach far beyond where you had been. ■

I am very hessitant to get involved in such an exchange, but since I have been brought up in this discussion as a participant, I will add that my memory of these past events matches Dr. Hustrulid's almost perfectly.

As to the original subject, we have several years of experience using DEM in chute design and have found it to be an excellent tool when used properly. ■