If my memory is correct the one excavator has a set of buckets mounted on a chain conveyor-hence the draging of material to a gathering conveyor.

This type of bucket wheel excavator/dredge was used by the french excavating the Suez canal as well as the Panama canal.

The standard bucket wheel excavator has a separate bucker which excavates/luffing the materials and then lifts and throws it on the conveyor belt to remove it to a loadout area.

The same excavator/reclaim unit uses the same conveyor to deliver product in reverse at a high rpm to facilitate stacking and throwing/casting of material to a stock pile.

References: Krupp ind., Orenstein and Koppel excavating machinery.

Caterpillar.com

I am sure there are more to look at- be sure to use a web browser to search for:

(Bucket wheel reclaimer)

(bucket wheel excavator)

(Bucket wheel trencher)

(bucket wheel dredge) ■

Hello Marcel de Bruin,

It seems you are referring to the machine which has bucket wheel mounted on slewing and luffing boom. The machine will be in two versions, named and identified as below by the bulk material handling industry :

1) Reclaimer or stacker cum reclaimer : In this type of machine, the bucket wheel picks up (excavates), the material from the stockpile which has been formed earlier by the same machine or other machine. Such type of excavation from the formed stockpile is simply called reclaiming.

2) Excavator : In this type of machine, it excavates (picks up / digs out) material from natural deposits of bulk material. Such deposits could be old in millions of years. Therefore, the excavator is more robust, more powerful and it will have variants in its construction to suit such functional requirements. Generally, the excavators will be crawler mounted, whereas the reclaimers could be crawler mounted or rail mounted.

It is not clear from your query whether you are referring to the bucket wheel reclaimer or to the bucket wheel excavator. Please clarify.

If you are referring the bucket wheel reclaimer, as per my memory (I am not searching the records), the difference in power for cell type and cell-less bucket wheel will not be double as mentioned by you, but could have limited difference. The book you have mentioned has also given the basic calculation procedure for power.

While deciding the power you have to also take in to consideration the size of bucket wheel which you will have to use when it is cell type and cell-less type. As I remember, cell type is needed when material is particularly abrasive and cell-less is used when material is average and it is more efficient in discharge (easy discharge).

Regards,

Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Besides the material characteristics and the power consumption is is the weigth which needs to be considered. Since each 1kg at the bucket wheel needs to be balanced at the counterweight boom. This, leading to a heavier substructure as well may end in about 3kg more weight of the whole machine. Morevover, cell type bucket wheels tend to block when excavating sticky material.

In so far there is a clear tendency towards cell less bucket wheels in excavation as well as in reclaimation. Krupp supplied two large cell leess type stacker reclaimers for iron ore to Ningbo harbour in 1995. Despite some initial concerns with the customer thes machines work fine so far despite operating in a very abrasive material.

Holger ■

Dear Mr. Holger,

I had given the general / relative considerations in selection. The opinion of the experienced & regular manufacturers of such machines naturally prevails.

I would like to mention that the abrasiveness of the iron ore can vary substantially. If you refer to the abrasiveness of iron ore, American practice mentions it in second category, one German publication mentions it somewhere around third category. In India, the iron ore is excavated and handled very extensively. The experience in India puts it in fourth category. The Indian iron ore is at some of the places is extremely abrasive. So, kindly see these differences in abrasiveness of iron ore while formulating your decision.

Regards,

Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Mr. Mulani,

I share with you that the abrasivity of the iron ore depends on certain criteria. However, in general it needs to be considered. Often it is also required to use the same reclaimer for ore and pellets. Pellets are sensitive to mecjanical pressure and quite often this is the reason to choose cell type bucket wheels. In Ningbo, however, the two Krupp cell-less reclaimers are also quite successfully used for pellets.

Another issue to be kept in mind is that iron ore may be extremely sticky, depending on the water content. With ore mined in a middle east country it was even almost impossible to use vibrating feeders. Irrespective of the power of excentric drives the ore stuck to the feeders.

Holger ■

Dear Mr. Holger,

I agree with you. The conflicting / confusing apparent observation (which I also had long time back), could be due to following reasons :

1) If the material abrasion is dominant, then one might have used cell type bucket wheel.

2) If stickiness is so dominant, riding the other issues, one may have used cell-less type bucket wheel. Then, abrasion issue might have been tackled by superior liner or somewhat slower speed etc.

3) Cell-less bucket does not have its own bottom plate to hold the material. So, its discharge is superior without doubt.

4) It seems that during course of time, new type of liners might have evolved (commercially usable), making it possible to use cell-less type bucket for abrasive material also, in a reasonable / acceptable manner. So, original concept about the choice might have got blurred. Therefore, general guidelines for selection may be looking somewhat confusive today.

5) Regarding the use of particular type of bucket wheel in boundary line situation, one has to make an inference from the existing installation regarding its suitability. To make this point more clear, suppose if you wish to use cell-less type bucket wheel for certain class of abrasive material, its commercial suitability can be assessed from the installation. Or one has to make his own test in appropriate manner to see the response of bucket wheel for particular material. This would be expensive and would demand efforts.

6) Suitability of cell-less type bucket wheel for iron ore pellets would depend upon mechanical strength of pellets, which could possibly vary as per my information from talk with an engineer concerned with steel plants. You may check about this. 30 years back, tendency was to use cell type bucket wheel for iron ore pellets. So, only rational guess could be that either pellet quality have improved or with the on-going experience people might have found that it is possible to use cell-less type bucket wheel for iron ore pellet also, in a commercially acceptable manner.

To summarize my reply I would only say that please look at these issues with an open mind because experience might have led to blurring of the choice for the application. However, fundamental characteristics of both types of bucket wheel are very apparent and clear.

Regards,

Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

To prevent the material from dropping out of the cell after being loosened by the buckets, they were uventually deleted from the design and the buckets were then sealed by a radial chute (so called ring chute/ cell - less wheel) which allowed the discharge of the material in a predetemined area only so that it could slide over a transfer chute onto the conveyor belt. This design was first used i the USA during the 1950s

email: www.natuanxd@mda.com

www.edu.org.com

tel: 0081 04 8387523 ■

Dear Mr. Debruin,

I have this book. Kindly let me know where it is written that cell-less bucket needs twice the power than cell type.

Yeah, cell less will require little more power than cell type because of the inner plate. But it is never twice.

Regards.

A.Banerjee ■

Dear Mr. Debruin,

Please you may try at your end & check.

Regards.

A.Banerjee ■

It has been a while since I have considered the different type bucket wheel designs and, because of the superior discharging ability, I thought that only cell-less type were now considered seriously.

The cell-less type bucket wheel requires a stationary, boom mounted retainer plate just inside the circumference of the bucket openings until the high point where the retainer plate is discontinued, allowing the material to drop into the receiving chute of the boom conveyor.

The Cell type wheel requires a vertical retainer plate against the cells which is discontinued, to release the load, when the cells are over the receiving chute. The friction on the retained material in this case produces less resisting torque because the material, in the cells, is closer the the center of the bucket wheel's rotation. This is why it take less energy to turn the bucket wheel in this case. The cell type wheel had the problem of a short time exposure for the matrial to release to the reclaim chute.

This gave impetus, in the 1970's, at Dravo Corporation, to the Star-Cell design, a cell type bucket wheel that increased the time exposure for release of the bulk material.

My two cents.

Joseph A. Dos Santos ■

Cell-less buckets are a more economical design considering that cell type bucket wheels are heavier in construction than cell-less type of similar capacities.

The heavy cell type bucket wheel necessiates a more robust boom and heavier sub-structure leading to higher capital and operating costs (heavier machine, heavier foundations, higher power requirement, etc).

Cell type will be more suitable for mining/ excavation work where this robustness and extra weight aids excavation. This also may be a better option for lump sizes > 150mm (especially iron ore).

For reclaiming of calibrated and loosely piled material I feel the overall power requirement in cell-less type will be less; as any increase in friction is more than compensated by the lesser weight of the rotating bucket wheel.

The main problems we have encountered with cell-less type is undesirable degradation in material size due to the friction. ■

Mr. Sidsahu,

I am not aware that the Cell-less bucket wheels weigh less. The structural support of the buckets is more difficult with the cell-less being entirely cantilevered from the outboard side of the bucket wheel. The Cell-type allows for additional support spokes on the inboard side of the wheel.

The argument that the heavier wheel requires more power has absolutely no merit since it does not require any power to turn the wheel (which is perfectly balanced around the shaft) regardless of the weight.

Joseph A. Dos Santos ■

Dear Mr. Sidsahu,

As regards weight & power the cell-less is little economical.But please check capacity with same wheel diameter & then compair cost economy.

Regards.

A.Banerjee ■