Instrumentation Inflight particle size analysis

Pete wrote:

This seems so obvious to me that I must be naive -- if you're talking
semi-portable that implies a guy going out there to do the measurement.
  So what about a shovel and a screen, or a shovel, a scale, and a screen?

There may be some higher-tech way of doing this (vision systems come to
mind, followed almost immediately of mental pictures of lenses caked
with dust).  But it's not my field, so I can't help you there.

Somewhere in between, what about a sampler in there someplace with a
screen?  If you were really clever you could put a little trommel with
the right sized holes in-line between point A and point B and measure
the rate of fall-through.  If you're lucky you may even be able to pour
the measured residue back into the screen, if it's not convenient to put
it into the waste pile.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

Getting a representative sample of the stuff on the train could be
tricky. I'd expect much more fines near the bottom of a carload that has
jostled down the tracks than at the top. In fact, the variation could
arise from that.

Jerry

P.S. The number 6.2 mm is interesting. Assuming that the wire in the
screen is about 1.5 mm diameter (about 15 AWG) that would make the
center-to-center spacing of the wires 6.35 mm, in other words,
quarter-inch mesh.
--
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oted text -

Thanks Tim and Jerry:

Tim, the only downside of the shovel and screen approach is having to
stop the belt. But if that is what it takes to get the results, then
so be it. I was hoping for an automated solution based on what I once
saw for an oversize determination - that was indeed a visual approach
consisting of a camera mounted vertically above the belt, pointing
down, and it scanned the top layer of the ore in real time. It kept up
with the belt running at full tilt, and digitised the image, drew
borders around the individual stones on the belt, determined their
sizes, and gave a percentage of oversized material on the belt. I
guess they made some kind of compensating assumptions about the
vertical distribution of the ore on the belt, but that's another
story. I do like your "sampler with a screen" - it would require some
mechanical modifications inside a chute to take a representative cut,
but not impossible.

Jerry, the profile of how the ore ends up in the orecar (after
travelling 500km) will undoubtedly show more fines on the bottom, but
then the car gets tipped upside down in the dumper anyway, and that
will mix the lot up again. I have noticed that, upon being stacked
onto the stockpiles, larger lumps of ore tend to roll down the sides
of the stockpile. The reclaimer would probably be capturing more fines
at the top of the stockpiles, and that is where our long sweeps in
feed to the screenhouse comes from.

Thanks again, and regards,

Pete

Tim, the only downside of the shovel and screen approach is having to
stop the belt. But if that is what it takes to get the results, then
so be it. I was hoping for an automated solution based on what I once
saw for an oversize determination - that was indeed a visual approach
consisting of a camera mounted vertically above the belt, pointing
down, and it scanned the top layer of the ore in real time. It kept up
with the belt running at full tilt, and digitised the image, drew
borders around the individual stones on the belt, determined their
sizes, and gave a percentage of oversized material on the belt. I
guess they made some kind of compensating assumptions about the
vertical distribution of the ore on the belt, but that's another
story. I do like your "sampler with a screen" - it would require some
mechanical modifications inside a chute to take a representative cut,
but not impossible.

Jerry, the profile of how the ore ends up in the orecar (after
travelling 500km) will undoubtedly show more fines on the bottom, but
then the car gets tipped upside down in the dumper anyway, and that
will mix the lot up again. I have noticed that, upon being stacked
onto the stockpiles, larger lumps of ore tend to roll down the sides
of the stockpile. The reclaimer would probably be capturing more fines
at the top of the stockpiles, and that is where our long sweeps in
feed to the screenhouse comes from.


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A google search like

http://www.google.ca/search?num  &hl=en&q=sample+from+gravel+crusher

or

http://www.google.ca/search?num  &hl=en&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=gravel+crusher+approved+mechanical+sampling+device&spell=1

may give some decent information such as

http://www.infratrans.gov.ab.ca/INFTRA_Content/docType233/Production/ATT38.pdf