Dear Shailesh Dalwadi,

The limiting factor will be the speed and belt width of your stacker. You should not exceed the capacity of the stacker belt with that of your yard belt.

Take the desired stacking tons per hour, calculate the speed required to achieve this with your stacker belt, then calculate the speed required to feed the stacker belt with your yard belt. Be careful to consider your transfer point, to avoid jamming and possible damage to the stacker belt. Also, ensure that the loading point for the yard belt is sufficient for your needs.

Regards, ■

Dear Mr. Dalwadi,

You have mentioned maximum lump size as (–) 150 mm.

I presume your specified 150mm is the maximum dimension of the lump in any one direction, as per usual definition.

It is also presumed that the 90% of material is less than half the maximum size. That is 90% of material is less than 75 mm, as per usual definition of ‘unsized’ material.

For the above mentioned size distribution of the material, the allowable maximum dimension of lump is 450mm, for 1200mm belt. Thus, the maximum lump size is less than half the allowable maximum lump size.

For the aforesaid sizing of material, the generally used maximum belt speed is 3.75 mps, for in-plant conveyors of 1200 mm belt, for handling of limestone.

The belt speed is subjective issue and opinion can vary somewhat. Higher speed can be used for long distance (cross-country) conveyors.

You need to use belt fabric and cover thickness to suit above speed and impact condition. The chute layout should also be complementary to material size, nature and speed. The boom conveyor will need thicker cover, and belt life (beyond warranty period) could be different for short conveyors and long conveyors in such system, which is to be accepted.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Another Thought:

A yard belt, with a horizontal orientation, is speed limited by the following:

1. Idler roll diameter and treatment of tolerances

2. discharge chute design and plugging during an aborted stop

3. oreintation of stacker position associated with point 2.

4. belt wear life due to adverse loading chute design

5. dust generation -- low dust means below 5 m/s belt speed

6. area wind direction associated with point 5.

7. noise generation

8. idler spacing, belt construction and lump size considered together

The belt can achieve a faster speed. Designer knowledge and general economic benefit would point toward a 4 m/s speed. I do know of yard belts running much faster carrying + 8000 t/h. The answer must be taken in context -- limited answer with limited data.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Pelletman:

Metric is good. Imperial is becomming the dinosaur. Your 1140 fpm is an agricultural 5.8 m/s. There are yard belts running over 6 m/s (1181 fpm) in many parts of the world for ship loading coal and iron ore.

There are yard belts running up to 10 m/s (1969 fpm) if you allow cross-yard stacking.

Bottom line for maximum speed usually is either transfer chute design and its implications, or dust. When dust is an issue then the upper limit is around 5 m/s for a P80 of 50 mm (+/-) and less for finer granular configurations to keep the Reynold's terminal settling velocity number within acceptable time limits for the nominated belt transport speed.

The thread starter is, I believe, refering to horizontally profiled belts operating with stackers that have your bumps. Thus, types of surface bumps are not normally considered or relevant for the yard belts.

You are correct about increased speed requires more power. However, I am a non-believer: a) 3 fold power increase is possible or, b) 2-fold power increase or, c) any such large number. The big number is parasitic losses (idler and pulley seal drag, scrapers, et al. ) that increase linearly with increased speed. The speed increase does reduce the crossectional area needed and may allow a reduction in belt and idler width with is consequential cost savings. Where is the optimum?

Another bit: belt life is, in part, caused by belt speed and transfer chute design. Today, transfer chute designs can yield a belt life well beyond 15 years. Speed becomes less relevant and can be increase well beyond old practices if you know how to design the correct chute geometry. This can not be taken in isolation. There are other arguements that may control the design.

Conveyorman ■

We run our belts OK - 1200mm at 3.2m/sec for limestone/clay and high grade limestone.

Your could go sloightly faster but I would not recc. it.

The main issue would be the stacker transfer and boom belt...esp. if the stacker is layer forming. This is where we have problems esp. in wet weather and belt cover wear.

James Morrish

Australia ■

James,

You speak of speed restrictions, with belts > 3.2m/s, at the stacker transfer boom due to?

Wet weather refers to sticky ore?

Belt wear refers to ore slippage on the belt?

Limestone/clay verses other products, such as the red mud field, is the problem maintenance, technology, .... ?

I would think that, aside from the high speed stacker and its right angle and sloped transfer, the transfer physics is the same for large and small conveyors, short and long conveyors, big and little capacities.

We see in Australia, Alcoa running better than 7 m/s and transfering well with red mud (sticky, fine particle size, .....

From these points I would ask you to elaborate on your experience and attempts to do better. Is cost an issue? Technical understanding an issue?

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Hi,

We had a packaged stacker/reclaimer.

Hence, for minimum tender cost, U get a lightweight, short stacker with low transfer heights etc.

The stacker is on the raw materails side of the cement plant - it is a blending stacker...boom conv. lenght is only 25m, hence, cycle time is very short.

Hence, handles, high grade limestone, limestone/clay (low mix).

We handle 3Mt pa of raw materials

The apparent material speed into the tripper car varies considerabley depending on the stacker direction...the trajectory is effected also

The stacker will be slewing soon.

Hence, transfer to the boom conveyor is an issue - the material trajectory, the carryback (45o chute angle, less on the valley), boom conv. belt wear, belt tracking etc.

The clay when wet is very sticky - is is not well mixed, hence, get problems in the poor transfer point.

We tried feed point deflectors but these are sensitive to bottom buildup > blockage....

We have a curved discharge point chute > had to get get the material to change direction to vertical about 400mm after the pulley!!!

Boom conveyor mis tracking is an issue when wet , less so when dry.

A proper stacker transfer would mean more height/distance > this means larger drive on the yard belt etc. I would also go for a wider and slower boom conveyor > less wear rate plus try to get all the material sitting on the bottom of the trough > less tendency to mis track.

I am not against high speed belts but U need to consider the total application.

Cheers

James ■

Dear Mr. Shailesh,

Belt speed depends on material characteristic,lumpsize factor & abrasiveness factors.Considering the all factors the max. speed should not be more than 2.8m/s for 1200mm belt width.I want to restrict to max. of 2.5m/s.If it is from mining application only ,speed can be increased slightly.More speed above this will cause degradation of LS.

Regards.

A.Banerjee ■

The maximum speed can be determined after reference to the good old CEMA or MHEA handbooks. The former is written using North American units whereas the latter began life as a metricated copy of CEMA.

If you wind up the belt speed remember to review your stockpile geometry. ■

Dear Mr Shailesh

I would run such a yard conveyor on -150mm limestone between 3 and 3.75m/sec if it were my conveyor, and to match the capacity.

Run too slow and your stacker radius gets too big

Run too fast and you get degradation and wear

Regards

LSL Tekpro ■

dear All

My question is what is the max . speed for a reversible conveyor of 5 m length?

lump size is-)13 mm for coal.

Belt weidth:2200 mm (may be varry as per max. speed )

Capacity: 1650 TPH

G. Pandey

Originally Posted by I G Mulani

Dear Mr. Dalwadi,

You have mentioned maximum lump size as (–) 150 mm.

I presume your specified 150mm is the maximum dimension of the lump in any one direction, as per usual definition.

It is also presumed that the 90% of material is less than half the maximum size. That is 90% of material is less than 75 mm, as per usual definition of ‘unsized’ material.

For the above mentioned size distribution of the material, the allowable maximum dimension of lump is 450mm, for 1200mm belt. Thus, the maximum lump size is less than half the allowable maximum lump size.

For the aforesaid sizing of material, the generally used maximum belt speed is 3.75 mps, for in-plant conveyors of 1200 mm belt, for handling of limestone.

The belt speed is subjective issue and opinion can vary somewhat. Higher speed can be used for long distance (cross-country) conveyors.

You need to use belt fabric and cover thickness to suit above speed and impact condition. The chute layout should also be complementary to material size, nature and speed. The boom conveyor will need thicker cover, and belt life (beyond warranty period) could be different for short conveyors and long conveyors in such system, which is to be accepted.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916

■