Please clarify whether you are referring to breaking of coal discharged by primary sampler, or at some other place. Is the grizzly mentioned by you, fed by primary sampler?

Regards,

Ishwar G Mulani.

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

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

The basic rule for the sampling system is that the sample should be taken and processed without any prejudice / selection. Therefore, the entire quantity of primary sampled coal should go into crusher, and then portion of this crusher output without any prejudice, should go towards secondary sample.

Accordingly, the presence of grizzly after primary sampler is not conforming to this basic rule. You need to use bigger crusher of appropriate type, to deal with the entire lot from primary sampler. You have three options:

1) If the system arrangement permits; then remove the grizzly and put a crusher which can deal with the primary sampled coal, in the condition as it is.

2) If the serial no. 1 is not feasible due to space restrictions, put small cross-conveyor of required belt width to receive discharge from primary sample and to feed into right type / size of crusher at suitable distance. Bring back the coal from this crusher output, into the existing sampling system.

3) If you cannot opt for serial no. 1 and 2, then think of putting the sampling system at some onward location in conveying system after secondary crushing. Here it will be dealing with smaller size coal. This will avoid big lump and thereby big crusher in sampling system.

I suggest you to contact reputed manufacturers of sampling systems also, to seek their advice.

Regards,

Ishwar G Mulani.

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

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Yes, you may be able to ram the coal through the grizzly and you and determine the ram size from the following procedure:

Break representative samples individually in a drop hammer test, by size, to get the Population Balance Model (PBM - such as JKTech process circuit simulator or other equivalent) Breakage Function (B). This gives you the surface energy liberated for the known lump volume/mass. From this data, a surface energy differential equation is determined that extends over a range of particle sizes that encompasses your product size distribution.

This gives you the scale up factor you need to find the energy to break pieces of any size. There is a little stretch, which can be worked out with our (CDI) rock/coal fracture mechanics model. The shape of the grizzly and administration of the ram need some definition. Pick them, model rock sizes and placements, with the selected ram kinematics, and the model will return all your points of interest.

As you noted, so much for sampling statistics. However, this can be addressed to a reasonable degree by more than one method.

Need more information contact us:

nordell@conveyor-dynamics.com

see our website: www.conveyor-dynamics.com for breakage sim.

I will be in South Africa for Beltcon 12 July 23-24. If you would like to get together give me your coordinates and timing.

Lawrence Nordell

Conveyor Dynamcis, Inc.

Bellingham, Washington ■