Originally Posted by kundu09

Can somebody share some ideas about the selection

of a bucket wheel in bucket wheel reclaimer regarding

bucket volume considering the fill factor.

The speed of bucket wheel rotation, the slewing speed of

the reclaimer boom and the size of the material reclaimed

rule all. ■

Hello,

Although bucket fill factor definition is same for bucket elevators and bucket wheel, but there is a difference in the result. In case of bucket elevators, the fill factor alone is adequate to decide elevator average capacity and peak capacity.

This is not so in case of stacker reclaimer machine having bucket wheel on boom. There is another additional element called reclaiming efficiency of the machine. The bucket fill factor and reclaiming efficiency together results into average hourly capacity. Typical example for explanation purpose is as below:

A) Boom length: 28 m.

B) Machine operational reclaiming efficiency: 73%.

C) Bucket filling factor: 94%.

D) Machine average hourly reclaiming rate, as per plant requirement: 1000 mtph.

E) Machine peak reclaiming rate: 1000 / 0.73 = 1370 mtph.

F) Calculate the bucket filling volume corresponding to 1370 mtph. In case of cell-less buckets this calculated volume also includes ring volume influence.

G) Bucket constructional volume: [F - (ring volume influence portion)] / 0.94.

The machine operational reclaiming efficiency is influenced by the shape of stockpile cross section. Triangular shape tends to make it poor, whereas trapezoidal shape with sufficient flat portion at top, tends to improve the reclaiming efficiency. Obviously, the machine inherent design, construction, automation, systematic operation, etc. equally contribute for the overall efficiency.

The machine overall reclaiming efficiency is calculated for specific application, in accordance with machine planned motions and automation. Its calculation is not very difficult, provided one has thorough knowledge about the machine operational features, various sequence of motions, time intervals corresponding to these motions, their automation and manual aspects, etc. occurring during 4 hours reclaiming.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

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Would a rake-reclaimer be a better bet? Would'nt it produce less damage to the pellets and provide better metrics on flow? ■

Dear Mr. Nordell,

Possibly you are referring to the use of scraper - reclaimer machine for iron ore pellets. If so, some information is as below:

1) Bucket wheel reclaiming action is like pay loader bucket which scoops the material, travels and then discharges material into hopper.

2) Scraper - reclaimer machine reclaiming action is like bull-dozer pushing / dragging material on ground and then finally pushing into ground level hopper. This process will have relatively more degradation of material compared to sr. no. 1).

3) Looking to more than 375 world-wide installations of scraper - reclaimer machines by German companies, I do not see its use for iron ore pellets. Based on this, it can be inferred that scraper - reclaimer is not preferred machine for iron ore pellets. Well, I do not mean it can never be used.

As for reclaiming efficiency; the ‘Traveling scraper - reclaimer machine having cut by luffing boom’; its reclaiming efficiency is more compared to bucket wheel on slewing - luffing boom. The reclaiming efficiency implies ratio of average reclaiming mtph to peak reclaiming mtph only, and it is not related to energy.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

I cannot speak for either. I have witnessed both. The multi-pin rake (Bridge) reclaim does not push the pellet. Its rake angle to ground is adjusted to be just shy of stability angle so that when rake agitates pile, pellets begin to roll and maintain rolling with subsequent rake pin disturbances. When pellet rolls to bottom of pile, a reclaim dragline then pulls pellets to conveyor transport. I imagine the dragline is used to control flooding between wet and dry environments. The rake I speak of has a triangular structural shape with multiple-pins at multiple levels - like a Japanese Pachinko (falling pelllet) machine.

There are different styles of rake-reclaimers. We have worked with a various bucket types, and for copper concentrate, phosphate materials, iron ore fines and pellets. ■