Check the website http://www.tamecservices.com.au .

The DunnEasy is available with inline/offset rolls at minimal <300mm spacing and no skirting that has to be removed to replace roll damage as in a standard idler set installation. A single person maintenance operation from the Safety of the access walkway. The DunnEasy design also is designed not to 'Plastic Deformation' under severe overloading situations which all slider impact beds or other XHD idler sets are prone to bending deformity and will maintain the skirting sealing without 'Puffing' dust spillage as used in Catenary or spring loaded idler sets. ■

Alex .. Simple answer.. Never.

Judging by the number of impact beds I have seen removed and chucked out, I would say never use impact beds.

They always seem to cause nasty belt damage.

On a Platinum mine near here, we chucked them all out and replaced with ROSTA sprung impact idler nests. Much better.

Cheers

LSL Tekpro ■

Both will work fine with a proper chute design. A pproper chute design will not have large deviations in impact force that causes belt dialation under the skirting.

I recommend rubber dust sealing at the skirt when a high degree of fines are present and there is a likelihood for strong flux in product flow.

Properly designed slider beds have an advantage in not allowing the skirt to move vertically with product impact pressure variations.

This can all be quantified with ROCKY, a new DEM code that gives the designer many tools to explore chute and skirt design options. ■

DEM is about as accurate as me playing darts blindfolded (before a few pints).

I always design chutes calculating the flow velocities all the way through, from first principles. This is extremely accurate, and allows me to ensure that the impact of any large lumps is less than 900 Joules, and that the exit velocity reasonably matches the belt speed. No need for special impact provisions.

LSL Tekpro ■

Graham,

I am supprised by your terse and erroneous comment. For your file, DEM is based on first principles. ■

Ah... maybe so Larry..

But every time I have had my chutes "audited" via an expensive "specialist" using DEM, they have got some really odd answers, which are of no use to man, woman nor beast. (Especially the woman who make our tea).

At least by designing entirely from first principles, and not relying on a complex computer programme (written by others) I can guarrantee the accuracy of the results.

It's not exactly rocket science,.. if you are a fan of Issac Newton.

Cheers

LSL Tekpro ■

Thank you for the insight into your combined genius and sense of humour. Does the tea lady work from first principles?

Part of the fun of designing with software is the discovery and understanding of the shortcomings. I used to take some automatically calculated properties at face value because a particular program worked so quickly elsewhere. Then one day I did a manual check and found the volumes of my stockpiles had been out by 4%. Like Sir Michael Caine didn't say."Not a lot of people know that."

How can someone get away with telling Lord Nel that it isn't rocket science?■

Aside from all of the good advice above, on chute design, when comparing impact beds to impact idlers or impact idlers with special spring suspension, or garlands that have no set hanging shape, it is a matter of energy absorption. Energy is defined at force times distance. For the same amount of energy to be absorbed (that of the falling material which must come to a stop vertically) the force will be reduced if the distance to stop is increased. The impact bed does not provide the travel distance so the energy is absorbed in squeezing and punching the belt against the bars. I agree with Graham, never use impact bars. If spillage is your problem (usually the motivation for using impact bars) use them only locally, on the sides, where the skirt seals bear against them.

Joe Dos Santos ■

are impact beds used for spillage? i thought they were used for IMPACT.....maybe i am wrong. ■

I do not sell impact beds or hold them close. I have seen many installations where they work and the clients are satisfied because they keep the work place clean. Why all the cynicism on impact beds. I do agree they can be misapplied.

If the chute is designed properly, the impact force (deformation) will be small, the skirt sealing then works well, and the seals can be quantified to a reasonably accurate value. You can tell by the lack of noise and dust as well as small belt wiggles. ■

By the way Larry..

We designed and commissioned an original impact arrangement for the loading point under a new and huge primary iron ore crusher (probably the largest crusher in the world?). The lumps to be handled are really big and heavy..

It works even better than we ever imagined, as it is so simple.

(Threaten me with a beer or two and I could even let you into how its done!)

Cheers

LSL Tekpro ■

Well I cannot refuse a cohort who is willing to stuff me with wine and beer. We all know there are some who have devine insite. My mind is willing to bend to the occasion.

Some of us have less bright rays of site and rely on the physics learned over many eons. DEM has given me and many others this assurance of better judgment. Let us see what you say when you find some little computer code can help the elevated cantalop do what's good for the client's of tomorrow.

I don't leave home without it. ■

Larry

I'm not much into wine. it gives me a headache, as does DEM which is about as much use as a CD of silent music, (but much more expensive)..

I look forward however, to being plied with beer, when I show you how to do transfers the "Spriggs" way, here in South Africa.

Cheers

LSL Tekpro ■

Tell us Graham,

Do you give the client a guarantee on the performance of your chute design for:

1. belt wear life

2. reduction in belt power

3. reduction in dust to acceptable level

4. guaranteed flow will not plug

5. noise level

6. liner wear and where, and what replacement rate.

7. belt tracking - hit or miss?

I would be eager to exchange difficult chutes that we each know work and see how the above are calibrated and guaranteed. Would we see the same result. Not likely. Do you want to take the challenge?

I assume you only know when it is installed.

We just did a large 9 chute DEM job for a client. Many changes were applied after client engineers made their best guesses. They appear to accept our recommendations for modes on evey chute.

The goals are simple. Show where to improve each and why by quantifying change behavior. How do you manage your designs and recommendations? Apply, test, measure, and receive client satisfaction. How do you know there might have been a better way that you did not apply. ■

Originally Posted by Graham Spriggs

DEM is about as accurate as me playing darts blindfolded (before a few pints).

I always design chutes calculating the flow velocities all the way through, from first principles. This is extremely accurate, and allows me to ensure that the impact of any large lumps is less than 900 Joules, and that the exit velocity reasonably matches the belt speed. No need for special impact provisions.

LSL Tekpro

Dear Experts,

How to calculate the impact force? If the lump is 1 kilogram ( 9.81 Newtons ) and vertical height is 1 metre, then is the impact force of the lump exerted on the belt 9.81 Joules?

Please correct me, if my understanding is wrong.

Thanks & regards, ■

Joule is the unit of energy, not force.

The name is in memoriam of the brewer James Prescott Joule in recognition of his various works with a carthorse and water well in the proximity of Manchester, Salford in fact. ■

Hi Louispanjang

Sir Isaac Newton had an apple fall on his head. It fell about one metre.

He immediately saw the Gravity of the situation and invented the Newton. He said "the force this apple exerts on my hand is a Newton", and went round to collect a total of 10 apples to prove it.

He had one kg of apples.

Anyway his mate Joule came along and said that "the energy absorbed by Newton's head was one Joule"

So you see.. one kg falling one metre imparts about 10 Joules

Cheers

LSL Tekpro ■

Originally Posted by louispanjang

Joule is the unit of energy, not force.

The name is in memoriam of the brewer James Prescott Joule in recognition of his various works with a carthorse and water well in the proximity of Manchester, Salford in fact.

Dear Experts,

I think Joule is the unit of work done.

If Joule is the unit of energy, what is Watt?

Regards, ■

Dears,

Watt is a secondary unit describing the power consumed when 1 Joule is converted in 1 second. It quantifies a rate of doing work which is usually refered to as power. Some people prefer to confuse by associating power just with electrical current.

The Watt is named after another James (Watt) who developed a relatively high performance steam engine. One of his prototypes stands outside Rutland Hall at Loughborough and provided a convenient student dewatering station in the early hours. Compared to this lot, that was a minor insult.

It would help us all if some parties were able to remember their schooldays or had listened to the teachers. Elementary physics, mechanics, applied mathemetics, or whatever someone chooses to call it, demands a knowledge of the units of measure.

On these forums we are regularly assailed by examiners who misuse the units of measure while still contesting the given advices.

I did once get caught out by a Langley but the unit itself is a bigger joke than the CIA who thought it up.

By the way, 1 kilogram does not equal 9.81 Newtons but 1 decaNewton does approximate to 1 kilogram force as any German worth the name will quicky confirm.

Can we please have symbols and sub/superscripts added to the text toolbar? Call me old fashioned, nothing new there, but I thought the nature of these forums was essentially technical.■

Hi Larry..

You asked if I give a guarrantee with my chute designs, well I never really thought of that..

You see no-one has ever broached the subject of a guarrantee with any of my designs, .. not that I can remember.

We do however have a policy, that everything we do has to be checked.

On three occasions we tried using DEM models done by so called "specialists" as checks. In all cases we could not use the information from the DEM's as they were obviously miles out.

So.. what we do now is get another bright LSL Tekpro engineer to do a full check from first principles.

Anyway, we do indeed address all the aspects you list, and definitely optimise the chutes wrt wear, centralised loading etc. Our new cunning approach to the calculation of material behaviour on reaching the belt below is a bit of a winner too, (and like me, it is quite simple!)

The trouble we are having is that some newer clients come to us and actually believe that DEM models are so pretty, that they must be right.. (and try to force us to use them). It takes a lot of time to show that a full analysis via our computer modelling from first principles is far more accurate, but we get there in the end, and have had good success. Still learning though..

Cheers

LSL Tekpro ■

Hi Graham,

Your comments about DEM are very accurate and totally relate to what we have found and that is the majority of DEM programmes commercially available are very inaccurate and therefore not worth using. I am however prepared to acknowledge that there are improvements coming and I am looking forward to using and checking Larry's new software against known applications. I believe eventually there will be means to calibrate and set up DEM software that will give more reliable answers. The key will be finding where the limitations are. Meanwhile when we do have very difficult material or a complex chute design issue we do use dynamic scale modeling which through Peter Donecker has proved to be very useful and very accurate. Like most things that work however it comes at a cost.

As far as the comments re guarantees etc. We work with our clients on the basis what we design will work regardless. As we are usually working with problem transfers that is fixing what others have designed we take the time to work out why what is in situ is not working and then working through options as to what are the solutions. Invariably there is always some compromise between production not wanting any constraints and maintenance wanting to maximise the maintenance outcomes as far as wear etc. It is rare indeed where we have a blank sheet of paper to work with or that an ideal solution can be configured once we have been constrained by the geometry of the conveyor system unless we are dealing with a relatively free flowing material such as coal.

Cheers

Colin Benjamin

Gulf Conveyor Systems Pty Ltd

www.conveyorsystemstechnology.com ■

Thank you Colin...

Your comments are like a breath of fresh air to me!

Incidentally, we recently checked the results of a DEM designed transfer against the design from first principles on my computer. It took them many attempts to get close, which made me think .. why not do it from first principles and get it right first go..??

And yes, no doubt it will come right eventually, but I think that one of the main problems is that many who run DEM's have sparkling clean finger nails, have never hid in a chute to get out of the rain, nor operated a number of plants for a year or two.

Cheers

LSL Tekpro ■

Hi Graham,

As you say, transfer chute design is still a very practical science where experience is important. That is why making unqualified comments about DEM that infers that all DEM programmes are the same and that DEM is reliable is so wrong as it is encouraging those that have clean hands as you say believe what they are doing is correct. We have a large number of examples where DEM was used to justify to a client a design only to find that the outcome was a disaster. The reality is most of these programmes infer just about any design will work possibly with a bit of tweaking whereas reality is far from this.

Cheers

Colin Benjamin

Gulf Conveyor systems Pty Ltd

www.conveyorsystemstechnology.com ■

As Colin says, experience is important.

I would recommend to anyone considering a greenfield development that they get someone like Colin with experience to do a paper review of the design in the first instance.

In so many cases, simple design flaws can be rectified or options discussed without any recourse to DEM or physical scale modelling in the first instance. I am talking about really basic stuff here.

When it gets more difficult and things are constrained, or when fine tuning is required, I can assist, as I often do for Colin and other clients. ■

Colin; Peter,

Do you now have ROCKY? What computer are you going to use it on?

We have a significant number of engineers and academics who practice chute design using ROCKY. Their observations will be made available. It is now going on sale at the end of June. Hopefuly, Colin and Peter can offer their unbias views. ■

Yes Larry, I have my copy and have had communication with J and Alex.

I will be using an Intel Core i7 2600K quad core processor and 16 GB ram. Much like the engineer in step 4 of your scenario in the overview on page 6 of the manual.

I am fairly busy just at present, but will read through the manual until I have some time clear to try the software. ■

Gentlemen,

To return to the original thread intent can somebody please advise if an impact bed can be mounted over, say, Bellville Washers; so that the loading damage can be mitigated to a level comparable to impact idlers? That way the spillage containment might be preserved and the impact force could be better calculated. ■

I would say forget the impact bed.

There are far superior ways of handling impact, as well as avoiding spillage.

Cheers

LSL Tekpro ■

I agree, if impact is such a probelm then you have a lousy transfer. Focus on the root cause and don't look for band aids that just create maintenance nightmares.

Cheers

Col Benjamin

Gulf Conveyor Systems Pty Ltd ■