dear Mr. Rosenthal:

A few years ago, Clouth developed and successsfully tested a belt with an ST8200 rating for the Henderson 2000 project in Colorafo. Before producing the belt, however, they determined that a lighter construction woulod suffice and used that rating instead.

You can get information on that direct from Clouth (or ContiTech).

Most of the large belt manufacturers are willing to develop higher strength belts, if there is a need. If you require current status reports on what is posssible, contact companies such as Continental/Clouth (Germany) and Goodyear (USA).

Hope this helps. ■

As a follow-up, I've been advised by Goodyear that they supplied an ST8000 steel cord belt for a project in Canada last year. ■

Dear Sr. Rosenthal,

Your interest in building a ST-10000 N/mm belt will surely capture the imagination of belt conveyor engineers and its creation will push the technical envelope to a new level.

You are correct in crediting Los Pelambres as the world's strongest rated belt @ ST-7800 N/mm. We collaborated with Krupp Canada is the system design including belt strength and splice analysis. However, this belt is not the strongest in terms of tensile carrying capacity. I will try to explain by examples. First, the splice carrying capacity is defined by its endurance or fatigue life. The fatigue life, in factory testing, ranges from DIN 22110 @ 10,000 load cycles to our criteria of 15,000 load cycles. A belt loop is cyclically stressed on a rotating 2 pulley machine from about 6% belt breaking strength (ST) to 50-60% ( common for higher rated belts) for the nominated cycles or until it fails (refer DIN 22110 for a diagram and explanation or visit our web site: www.conveyor-dynamics.com then about/innovations in/splice analysis). If it achieves the set load cycles say at 50% of the ST then the belt true tensile and splice endurance or fatigue rating is said to be 50%. Multiplying the ST by splice endurance efficiency yields the tensile capacity. The following examples show why.

Project ST (N/mm) Efficiency Splice ST(N/mm)

1. Prosper Haniel 1986 (a) 7500 0.367 2750

2. Palabora 1988 (b) 6600 0.510 3300

3. El Abra 1996 (a) 6800 0.500 3400

4. Los Pelambres 2000 (a) 7800 0.500 3900

5. Muskege River 2002 (c) 7000 0.560 3920

6. Recent testing 2002 (c) 8000 0.510 4080

legend: (a) Phoenix, (b) ContiTech, (c) Goodyear

Ultimately the splice capacity governs the ST rating once the peak steady-state belt tension is determined. I have published may papers on the subject which are listed on our web site.

Conveyor Dynamics Inc. built the world's strongest splice testing machine that has the capacity to do ST-10000 N/mm. It has twice the strength of Hanover Univ. and is equipped with advance instrumentation to probe the nature of rubber and cord failures. Goodyear now owns and operates the machine. We have tested belts to ST-8900 N/mm on this machine.

Yes, I believe the belt can be built and tested. Mr. Miller is incorrect in stating Goodyear have a belt in service at ST-8000. This is the Canadian Muskege River system with a belt rating of ST-7000 N/mm.

I state again, the splice strength is more important than the ST rating. You must establish the splice endurance efficiency. If your are using the conventional belt safety factor SF=6.7:1 , then the St-10000 N/mm has a splice strength of 3600 N/mm. From the above examples, a ST-7000 n/mm with an efficiency rating = 0.510 yields the same splice strength as the St-10000 N/mm.

We would appreciate the opportunity to assist Chuquicamata in defining the true belt strength requirements and testing procedures. I am happy to send you our relevant publications on the above topics.

With Best Regards,

Lawrence K. Nordell

President

Conveyor Dynamics, Inc.

1111 West Holly St.

Bellingham, Washington, USA 98226

ph: 360-671-2200

fx: 360-671-8450

email: nordell@conveyor-dynamics.com

website: www.conveyor-dynamics.com ■

Sr. Rosenthal,

Part II: ST-10000 N/mm Belt Design

Thank you for your response. I would like to add a further note on the feasibility of a ST-10000 n/mm belt design after making a brief analysis.

Assuming the cable could be made to the strength of 200 kN and the cable diameter did not exceed 14 mm. Then 90 cables would be required at a pitch of 19.83mm for a 1829mm (72 inch) belt width. A six (6) step spl;ice would have the necessary gap of 3 mm and the gap to cable diameter of 0.215:1. All feasible.

However, there are only a few belt presses world-wide that can construct the belt with a 14mm cable. I do not think there are any presses that can do 15 mm cable diameter. I do not know if a 200 kN breaking strength can be made in 14 mm. It will probably take a special high carbon steel.

The normal strength for 14 mm is in the range of 175 kN. At this 175 kN strength, even a 7 step splice does not provide enough rubber gap in the splice. In any case, you are hitting many limits - wire rope mfg., belt mfg press design, testing of splice integrity, field vulcanizer; etc.

To date, we have tested a 5-step splice design at ST-8900 N/mm to a 50% endurance efficiency. the splice was 7 m long. Getting the last 1100 N/mm is a big step.

The splice step lengths, for the ST-10000 would need to be on the order of 1700 mm/step for close to a 11 meter overall splice. The only test facility in the world that can handle such a belt is at the Goodyear factory with its 12m pulley pitch. The pulley diameter for the test would need to be over 2m to keep the pulley bending stresses from having a strong influence on the fatigue rating.

The pulley diameter would need to exceed 2.5m in operation.

Wishing you success in your ST-10000 N/mm quest.

Lawrence Nordell

President

Conveyor Dynamics, Inc. ■

`2w1e ■

Dear John,

Subject: Intermediate Drive Station - Hard Rock Tunnel Application

You bring up a valuable point that should be debated for the general good. Resolution is not the short excercise we practice in this forum. For my part, I appologize, in advance, if I seem to come down strongly on one side of this debate. My wish is to incite the collective.

Speaking for Sr. Rosenthal, he is refering to an underground hard rock slope belt installation. This is quiet different from coal. The operators go to great expense to avoid transfer stations. The risk to the ~500 million dollar installation is very significant. Belt rip or damage, from tramp metal and slabby rock, is to frequent to double the investment risk.

The transfer will be significantly larger for primary crushed hard rock than for coal. It will require a greater excavation chamber, larger maintenance access and maintenance equipment handling systems.

If the conveyor must be split into two sections, there are other added costs. The steel cord belt takeup is more difficult when placed underground. Belt reel handling and its splice table is expensive plus it is more than doubled the cost of the single head drive.

The drive station and pulley handling will be significant in size and expense when buried underground. Electrical and istrumentation routing and housing for MCC/ Instrumentation/Control, and HVACC are more difficult to accomodate and are significantly more expensive place underground. The two conveyors need to be coordinated and collectively controlled from a central control room place at one end of the system. Access to tranfer chute and its liners, dust and noise control, large equipment handling and tunnel excavation clearances will all drive up costs.

The common number used to measure risk is the lost profit due to downtime. This is often tariffed at +/- $50,000 / hr. or $ 1 million per day. The added second drive station will cut in halve the systems availability from 1% to 2% in round numbers. This penalty cost should be added to the production cost.

Maintenance cost (labor, et al) will be more with two drive systems, and with the underground placement.

Your idea of a two pulley drive will require many more pulleys with dirty side contact that may unstablize the load sharing due to the potential of clay type buildup on the pulley surfaces near the drives. Here you fight for space that is abundant above ground.

I would be willing to bet the belt savings will disappear when all capital cost are weighed. The far more compelling expense is the risk to investment. I estimate the additional transfer station and its associated costs will be at or above 2 million dollars. The two drive station, with belt and ancillary savings, will be at or below 1.6 million dollars. This excludes any risk penalty costs of the second transfer.

Aside from these comments, anticipating the ST-10,000 N/mm belt can be successfully built, its cost, availability and certification of performance must be put to the manufacturers.

I am sure others can add more insite and valuable comments to further the common interest of the question.

Lawrence Nordell

President

Conveyor Dynamics, Inc.

1111 West Holly St.

Bellingham, Washington 98225

USA

ph: 360-671-2200

fx: 360-671-8450

email: nordell@conveyor-dynamics.com ■

John; Sr. Rosenthal,

RE: Three Missing Memories

Sorry for the lapse in memory.

1. An important factor in the above equation, not previously stated, is belt wear. Two transfer stations will double the rate of wear. With a so-so chute design, this might lead to an early belt replacement thereby loosing any advantage of cutting the strength by about two. Some how you pay more for two. I also don't quite understand how you cut the belt in two and get less than half strength. I would intuit the opposite.

2. Another implication which I should have completed. With a loss of 1% availability you loose 1% of your productivity or you increase the make up rate. Given you loose 1% productivity with two drive stations then I claim you loose !% of say 5600 hours per year or 56 hours. At, $50000/hr this is $2.8 million. Argue along the curve, it still is going to amount to a big number. Too many losses and too few benefits make an imbalance favoring one belt to two.

3. We cut the length of a conveyor when the spares costs outways the risk cost of failure. This may be in the neighborhood of 25 km.

Viva Vino Tinto

Lawrence Nordell

Conveyor Dynamics, Inc. ■

It's been interesting following the threads in this conversation especially since we've been involved in the project for sometime now and I presume that our comments made during the progress of the work has sparked the conversation.

The question of ST 10,000 came up early in the project and a comment was made that one of the manufacturers claimed it could be built. I don't doubt this at all as it's only a matter of physics and the ability to cram all of these huge steel cables into a very compact area and hope that one achieves good rubber impreganation during the cooking process.

So, can it be built? I say Yes. However, Nordell is right in stating that the more important figure to consider is splice efficciency. What good is an St 10,000 belt if the splice efficency is less than adequate? I doubt that the manufacturer mentioned what the splice efficiency would be in the conversation as they likely didn't know an accurate value. It's doubtful that it would be anywhere near 50%.

Splice efficency has increaed dramatically in the last few years, mostly due to the work carried out at the Univ. of Hanover and by Nordell. You dont have to be a rocket scientist, though, to know that a steel cord belt is only as strong as it's splice. By increasing the strength at the splice you can reduce the stated ST rating of the belt.

We designed Los Pelambres (LPL) and determined the correct belt rating to be ST 7800 (actually ST 8400 derated to ST 7800 to satisfy DIN code) and, as Nordell mentions, the splice efficiency proved to be greater than 50%. So, technically speaking, this is the strongest belt in the world but that is not what this discussion is all about.

The client is attempting to design an underground conveyor system handling coarse crushed copper ore. The fewer transfer areas, the better, as each one represents an enormous amount of capital. There is no need to split the conveyor into two flights. Power and drive technology for the conveyor as discussed is available but we'll be stretching the envelope once again on some of the mechanical components. That's Ok, nothing new for us.

However, the answer to building the system doesn't lie with finding someone who can manufacture a belt with a belt rating of ST 10,000. There are numeorus straight forward solutions that can be considered for the project and I'm surprised that no one has mentioned them yet.

best regards,

Steve @ Krupp ■

Hello all from a first time poster ... terrific site we have here.

Through my involvement in the design and specifications for the forementioned ST-7000 conveyor perhaps I can contribute some background.

Working at a new opening of an open-pit oilsands mine, this conveyor will not realize its full potential until the conveyor is extended down into the pit. Alternate belt rating (~ST-4000) was considered for the initial installation.

Consider some data:

Belt width 2400 mm

speed 5.5 m/s

cable quantity 124

diameter 12.4 mm

pitch 18.9 mm

breaking strength 138 kN each

This means (excluding covers) the carcass is ~50% steel by volume and the combined breaking strength of these cables is 17,112 kN.

The spilce was done with a Shaw-Almax sectional press; a practical solution considering the splice area (2.4 m wide belt with a 4@1.6 steps plus bend zone plus bias = ~8 m splice length).

Now, back to Steve's point regarding simple solutions ... use a wider belt and/or increase speed to reduce tension. ■

An excellent thread here, particularly because the oft-ignored factor of splice strength has been unequivocally highlighted.

This brings me to my question : is there any international specification which spells out the METHOD OF TESTING the splice joint strength of TEXTILE BELTING ? ■

KAYEM:

Good question. You won't like the answer.

There is no standard on fabric. There is a lot more variation in construction techniques, fabric types, and in splice types than with steel cord. One could write a book on it. Do a simple examination. Put a 3 or 4 ply pattern together and build a mfgs. catalog splice. Study the transfer of shear stresses by the conventional method. What happens to the tensile capacity of the remaining plies at the butt joint of any fabric ply?

At the joint, the remaining plies must carry the load across the gap. Furthermore, the adjacent fabric ply or plies sees an even greater local tensile stress rise in the fabric, and interply rubber shear stress. Need to do an FEM analysis to get close.

This is one of the reasons for special treatment, among some knowledgeable types, of the splice. Especially true with reduced plies.

Thus, why do fabric belts have high safety factor ratings such as SF= 10:1 or 12:1? It is because of the splice foremost. Elastic incompatibility is another issue. The fabric elongation and interply rubber shear deformation must be considered. Normally,not done. If it was done splice materials would be changed. You do not see FEM on fabrics and alternative splice procedures because the clients do not support the research. It is difficlt enough to get some conformity on steel cord. This is due to thebig buck ticket and risk.

Another reason for the high SF is due to construction difficulties in obtaining equal axial and transverse fiber loads in the belt press . Watch construction of fabric belts in the factory. There can be a great difference in the fabric behavior which leads to loss of capacity. Big SF hides the issues.

A brief Comment -- VLT (viva la tinto)

Lawrence Nordell

Conveyor Dynamcis, Inc. ■

Gabriel:

Many have researched fabric splice behavior using FEM. You are aware of the CDI research used to reinforce steel cord splices and for improving fabric splices strength using FEM. FEM helps to identify the elastic incompatabilities between rubber and fabric in the critical shear zones. Changes to the elasticity compatability field can be applied to improve fabric splice dynamic (fatigue) strength by more than 25%.

Bulk Solids has references from Australia from a number of years ago. Goodyear, Dupont (kevlar), and other belt manufacturers have applied research to the subject. Unfortunately, no standard has emerged.

I am sure, some of the lack of publication deals with intellectual property. There is a lot more latitude in fabric designs than in steel cord alternative constructions. Add to this the differences in splice configurations, and we see there is potential for significant improvement. Who funds the research?

Lawrence Nordell

Coonveyor Dynamcis, Inc. ■