Resistance factors are idler spacing, seal drag, sag, rolling resistance of the belt itself, scrapers, plows. Dynamic analysis takes all the resistances into consideration. ■

Originally Posted by Himanshu

To all Concerned,

How does the resistances to motion of belt vary with belt speed in a trough belt conveyor (regardless of conveyor length), during acceleration and braking conditions?

Regards,

Himanshu

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Increased indention rolling resistance is non-linearly proportional to increase in speed. Speed can be converted to a temperature base solution using the WLF equation, if you already have knowledge of rubber viscoelastic properties. If not best to either talk to a belt supplier that has this technology such as Goodyear, Bridgestone, or other, or work with a consulting house that has this technology. Goodyear and Bridgestone have used the CDI based rubber rheology model, since it is proven on many overland systems with a large body of field measurements. ■

Originally Posted by nordell

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Increased indention rolling resistance is non-linearly proportional to increase in speed. Speed can be converted to a temperature base solution using the WLF equation, if you already have knowledge of rubber viscoelastic properties. If not best to either talk to a belt supplier that has this technology such as Goodyear, Bridgestone, or other, or work with a consulting house that has this technology. Goodyear and Bridgestone have used the CDI based rubber rheology model, since it is proven on many overland systems with a large body of field measurements.

Common idea is that the belt conveyor resistance is more or less constant throughout its regime from starting to running. If it varies with velocity, then it will affect transient velocities during starting compared to the scenario when the resistance is considered almost equal from zero velocity to final velocity. I think the initiator of the thread precisely wants to know that whether he should consider variable resistance or fixed resistance in his dynamic analysis. The variable resistance with respect to velocity helps to stabilize the running velocity when the resistance at rated velocity is known. ■

Originally Posted by ambhad

Common idea is that the belt conveyor resistance is more or less constant throughout its regime from starting to running. If it varies with velocity, then it will affect transient velocities during starting compared to the scenario when the resistance is considered almost equal from zero velocity to final velocity. I think the initiator of the thread precisely wants to know that whether he should consider variable resistance or fixed resistance in his dynamic analysis. The variable resistance with respect to velocity helps to stabilize the running velocity when the resistance at rated velocity is known.

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Only if his belt speed exceeds 7 m/s, probably more like 10 m/s, and has a large temperature swing with a very sensitive rubber strain rate. Are we trying to enlighten or direct interest in future designs? There are so many ways conveyors can be improved well beyond present day published information. Is India able to apply any new developments? Belt speed standards are still at 4 m/s, belt safety factors at 7:1, buy ugly belt with ugly performance, ugly idlers, ugly pulleys. They put horrific counterweigths in center of end disk?

"Buy China" because India engineers cannot take the initative and responsibility.

The main point is the thread starter probably has no idea about rubber and its physics and behavior under ranges of strain, strain rate, idler features, temperature, belt cover thickness and properties, et al., much less on the dynamic effects.

I guess my comment should have been: "probably not" if he cannot get statics correct. The crude calculation methods most often applied do not consider the range of variables. What is the difference to error by 50% but stay within stress limits? If the client knew the penalty in performance, ownership cost, etc. then the engineering standards would become more focused. Until, clients take notice, business as usual. Worry about the micro details, when you don't know the macro effects.

CDI have worked in India for a substantial number of years. Today, most Consulting Firms have little knowledge about rubber, design optimization methods, and care less. They demand their way is the only way, even though the cost to a client adds into the millions of dollars. They are cost conscience of a bolt, an ancient standard, old steel, and follow the past and not the future. India will wallow in the engineering backwater until they overcome their fright in the vision of the future. Few engineers stray outside or visit modern operations to learn what can be done. Ask critical questions as engineers, not ask "why me lord".

For example, CDI designed 7 km Mundra and 5-14 km Dahej port @ 6000 t/h belt conveyors. Adani/CDI used LRR belt bottom cover and run at 7.5 m/s. Mundra just set India Port records for tons transported in 24 hours. Highly reliable, low down time, energy efficient, and lowest CAPEX & OPEX cost to transport tonnage. New belt and idler construction. Who now takes up this practice? Engineers come and witness the elevated truss, mobile trolley, large span trusses, and horizontal curved systems, but, cannot take action to do the same elsewhere. Witness two conveyors side-by-side, one Modern Conveyor and one "Not-So". Both installed at the same time. "Not-So" client drives by the Modern Conveyor and says "why couldn't I have that one?" It transports more, cost less, down less, spills less, easy access, still looks new after 4 years. "Not-So" dust clouds, at the transfer stations, don't make neighborhood friends. ■

Originally Posted by nordell

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Only if his belt speed exceeds 7 m/s, probably more like 10 m/s, and has a large temperature swing with a very sensitive rubber strain rate. Are we trying to enlighten or direct interest in future designs? There are so many ways conveyors can be improved well beyond present day published information. Is India able to apply any new developments? Belt speed standards are still at 4 m/s, belt safety factors at 7:1, buy ugly belt with ugly performance, ugly idlers, ugly pulleys. They put horrific counterweigths in center of end disk?

"Buy China" because India engineers cannot take the initative and responsibility.

The main point is the thread starter probably has no idea about rubber and its physics and behavior under ranges of strain, strain rate, idler features, temperature, belt cover thickness and properties, et al., much less on the dynamic effects.

I guess my comment should have been: "probably not" if he cannot get statics correct. The crude calculation methods most often applied do not consider the range of variables. What is the difference to error by 50% but stay within stress limits? If the client knew the penalty in performance, ownership cost, etc. then the engineering standards would become more focused. Until, clients take notice, business as usual. Worry about the micro details, when you don't know the macro effects.

CDI have worked in India for a substantial number of years. Today, most Consulting Firms have little knowledge about rubber, design optimization methods, and care less. They demand their way is the only way, even though the cost to a client adds into the millions of dollars. They are cost conscience of a bolt, an ancient standard, old steel, and follow the past and not the future. India will wallow in the engineering backwater until they overcome their fright in the vision of the future. Few engineers stray outside or visit modern operations to learn what can be done. Ask critical questions as engineers, not ask "why me lord".

For example, CDI designed 7 km Mundra and 5-14 km Dahej port @ 6000 t/h belt conveyors. Adani/CDI used LRR belt bottom cover and run at 7.5 m/s. Mundra just set India Port records for tons transported in 24 hours. Highly reliable, low down time, energy efficient, and lowest CAPEX & OPEX cost to transport tonnage. New belt and idler construction. Who now takes up this practice? Engineers come and witness the elevated truss, mobile trolley, large span trusses, and horizontal curved systems, but, cannot take action to do the same elsewhere. Witness two conveyors side-by-side, one Modern Conveyor and one "Not-So". Both installed at the same time. "Not-So" client drives by the Modern Conveyor and says "why couldn't I have that one?" It transports more, cost less, down less, spills less, easy access, still looks new after 4 years. "Not-So" dust clouds, at the transfer stations, don't make neighborhood friends.

Dear Nordel,

Giving value to your comments and sentiments, I am of the opinion that you skirted the technical question carefully. Not that in India people are completely unaware of all items you mentioned, but the academic question of a beginner should not be discouraged in the forum. Regards ■

Originally Posted by ambhad

Dear Nordel,

Giving value to your comments and sentiments, I am of the opinion that you skirted the technical question carefully. Not that in India people are completely unaware of all items you mentioned, but the academic question of a beginner should not be discouraged in the forum. Regards

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I said power varies with speed as the inverse of temperature, but, not so much till belt speed exceeds 7 m/s. Even at higher speed, if we analyze the system as a full speed steady-state drag, from zero to full speed, there is little engineering difference. No one, to my knowledge, will analyze the true rubber mechanics in a dynamic analysis model. There are so many more important points that must be considered, new vs. used belt, worn belt, FR vs. LRR, summer vs. winter, day vs. night, belt speed vs. bearing drag, lubricant vs. temperature influence on bearing drag, conveyor alignment, idler TIR, et al.

I am not aware of your engineering prowess. I talk to you as an equal.

I am frustrated with so many large Indian consulting houses putting marginally knowledgeable managers in charge of major projects that dumb-down modern optimizing design techniques. Designing to their standards is like designing to 1980's. Now 34 years later, times have changed what we know about design optimization. How do you avoid pitfalls of poor designs? Go to the manufacturer’s site and witness the mfg. For instance, go to 4-5 idler shops you are considering to supply their product. Walk through the shop and twist the shafts of rollers. You will likely find a large range of resistance. How much is too much? It is sad the shoddy work passes inspection. Poor quality control is acceptable, because no body does due diligence. I have been to over 8 shops at last count, only 2 make idlers I would purchase for an Overland Conveyor project. These shops are world class. Pulley supply is even worse, noting a large pulley mfgr. welding large CWT plates to the end disk. One pulley failed on the end disk CWT plate at its weld. The site has more pulleys that will see the same faith. The point is what happened to the consultant's due diligence?

Above that, I bet a good lunch, neither consultant nor mfg. knows why they weld the crazy balance weights (CWT) on the pulley to begin with. Balance weights are an artifact of placing pulleys on extended-cantilever structures. Do the sums and publish the results for all to see. Take a 5 or 10 kg weight and rotate it at one rev/sec. Can you hold on? Yes, and that is the same force the balance weight is applying to the bearing. So why do it? I believe the balance tells you how poorly the pulley is fabricated with a lopsided mass. Nothing more, except for extended/cataliver trusses.

When someone says do a dynamic analysis, what does it mean. There are about 5-8 dynamic analysis routines being used. Few are very accurate. Yet the layman has no clue if the analysis is accurate or a pretty picture. If the consultant does their job correctly, they will ask for evidence on performance on static and dynamic conditions.

Sorry for the rant. ■

Dear Mr.Larry,

Like idlers or fabric conveyor belts, is there any standards ( particularly for dimensions ) for conveyor pulleys ?

Regards, ■

Originally Posted by sganesh

Dear Mr.Larry,

Like idlers or fabric conveyor belts, is there any standards ( particularly for dimensions ) for conveyor pulleys ?

Regards,

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I am not versed on International Standards. I Googled " ISO Conveyor Belt Pulley Standards and best bet was a Sandvik Pamphlet:

http://www.miningandconstruction.sandvik.com/sandvik/0120/Internet/Global/S003713.nsf/Alldocs/Products*5CConveyors*and*conveyor*components*5CPulleys*2ALocking*element*pulleys*Light*duty/$file/Pulley-select.pdf

You can request the CEMA Standards, which will give good guidance. I have not memorized their method. Therefore, I will only speak of my experience, but, will not elaborate.

I am not endorsing this Sandvik phamphlet, only bringing the concept of many pages to focus on its depth. Our internal design standards go far beyond this as I am sure does Sandvik.

In a effort to answer your dimensional question, I can give some pointers on steel cord, which is the simpler to quantify:

1. Pulley diameters should be based on the construction of the steel cord: % belt tension, arc contact length, bottom cover thickness, and belt safety factor: ........... 100 x cord diameter for below 75% of rated working tension and 150 x cord diameter above 75 % rated working tension for Best SF >= 6.7:1

2. Pulley face width above belt width: ........................ A) 100 mm for belt width up to 1000 mm, ST-1000 N/mm, belt speeds to 4 m/s, and no horizontal curves. B) With horiz. curves ... 150 mm; C) belt width >1000 mm, speed > 4 m/s, >ST-1500 N/mm, use 200 mm; belt width > 2000 mm, speed > 6 m/s, >ST-3000 N/mm, use 250 mm; Speed >=7.5 m/s, belt width > 2500 mm, >ST-6000, use 300 mm. All pipe conveyors use 300 mm adder. due to snake action and loading dynamics that rotate pipe conveyor, unless you use well designed Confine Construction.

In short, you must provide allowance for the belt to misalign according to ISO, DIN, CEMA, which roughly is 6% of belt width. In addition, you must allow for poor splice construction alignment (what client will allow and operate that some will argue should be in 6%); ~ 100 mm; poor tracking at loading station that also depends on tonnage rating - higher tonnage = greater error in tracking, also alignment of discharge and receiving conveyor can influence allowance - best to minimize loading error by DEM analysis of flow onto belt that gives lateral thrust = degree of misalignment.

The above are pulled from my memory. Please use with caution, except for Graham.

3. Shafting ...... to big for this discussion.

Hope you find this of some help. ■