Dear Banarjee

minimum pipe dia can be calculated based on 3 times of lump size or 70-75 percent filling which ever is higher

A R SINGH ■

I suggest you consider the lump size at its longest projected length and not the screen size length. I further suggest some allowance (50mm) be applied beyond the 3 x lump size rule to assure the bound rock can wiggle free when pinched in the idler trough configuration. ■

Dear Banarjee

In addition to Maximum size of lump as indicated by Mr nordell you have to see sieve analyses of material in case maximum lumps are in the range of 25-30 percent than pipe conveyor may be slightly on lower side however percentage of 200 size lumps are more han 70-80 percent you may have to go for sligtly higher pipe diameter. It is very difficult to predict third direction of lumps i sggest in case if maximum size in third direction is not predictable avoid using pipe conveyor for such big lump sizes.

By chance if at any time material cossection inside pipe is bigger than pipe dia your system will fail as projected side of belt will obstract in between pipe forming fixed rollers.

A R SINGH ■

Dear Banerjee

650 mm pipe dia for 70 percent 200 lump size seems to be theritically ok. However please ensure lump size in any direction is more than 200 mm

A R SINGH ■

The comments on the selection criteria satisfy some of the necessary engineering factors but not all.

Mr. Singh noted that the sieve analysis is important and may influence the pipe diameter and costs which couold lead to another diameter recommendation.

A 650 mm diameter pipe requires a 2200 mm wide belt and is 28%loaded when run at 3m/s. THis is not an economical solution.

I do not believe the client would approve. If the belt is very short maybe. For any pipe over 1km, other engineering judgements shold be considered including reducing the lump size or investigating the size distribution and its impact on the diameter selection. ■

Dear Mr. Banerjee,

It has been mentioned by you that 200 mm lump are 70% in iron ore. Kindly clarify the meaning of this whether :

- 70% of 200 mm size lump implies that 70% of material has size raging from 200 mm to fines.

- 70% of material is of 200 mm size lumps.

Please also clarify how are you creating this type of size gradation i.e. whether as an output of some crusher or whether by selective segregation by screening.

Probably it should be simply output from some crusher. If it is so its size will always be varying from fines to the size you are referring. The pipe conveyor selection depends upon the exact meaning of the size particulars mentioned by you. If you are inferring this size on the basis of crushing elements gap then also inform the crusher’s setting for this gap dimension.

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 ■

I believe it would be prudent (and definitely economical) to further crush the ore before loading it on to a pipe conveyor. Your suggested pipe diameter is already transgressing to belt widths which restrict vendors to just a few worldwide and prohibit serious competition. Further with such a wide belt you would need a very stiff (and therefore, heavy) pipe belt and this means unnecessary power consumption.

A pipe belt should ideally be selected based on capacity and the lump size restriction should be adopted as a check whereas in this case the pipe diameter selection is being based on lump size constraints - not the best approach. ■

Dear Mr. Banerjee,

the question for the crusher is correct. You should be aware that in particular jaw crushers or gyratory crushers porduce so called fishes, which are lumps passing a certain screen but beeing quite long, sometimes twice the screen mesh or more. This happens in particular if the crusher is not fully loaded, i.e. during start-up or shut down.

Best regards

Holger Lieberwirth ■