Crushing, Screening & Conveying

Crushing, Screening & Conveying 2017-04-04T06:57:13+00:00
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CRUSHER SETTING LIMITS (5 replies and 1 comment)

Paul Morrow
11 months ago
Paul Morrow 11 months ago

All Metso C-Series Crusher models have a maximum possible setting as well as a minimum allowed setting, and Metso claims it is very important that the user understands why these are important to keep these in mind at all times.

The maximum possible setting is simply the maximum setting that the Crusher is physically able to accommodate. Typically, such setting is indicated with new jaw dies, and the setting actually depends on the jaw die profile as well as on whether a spacer is being used or not. 

The minimum allowed setting (c.s.s. or o.s.s.) is the minimum setting at which the Crusher can be used when the Crusher is operated according to Metso’s recommendations. Metso warns the minimum allowed setting is very important as it takes into account the design and operation limits of the Crusher. Metso states not respecting these recommendations can lead to a poor utilization of the jaw dies (high scrap rate) as well as a shortened Crusher life.

I have a C106 to run. Is the Metso talk just fear mongering voodoo or real?

I want to crush as fine as I can. Metso is telling me to run as if I had hard rock or my warranty will be voided. Tell are not telling me what my Mpa actually is. (All I know is my BWi = 15).

What hardness test do I perform to confirm my rock's Mpa?

Thank you!

Alex Doll
11 months ago
Alex Doll 11 months ago

The value they are describing is a rock mechanics (or geomechanics or geotechnical) test called the "unconfined compressive strength", or UCS for short.  It is sometimes also called the uniaxial compressive strength text to distinguish it from the triaxial test.  You can see more about the test on this appropriately named web page:


Paul Morrow
11 months ago
Paul Morrow 11 months ago

Thank you Alex.
Is the Metso talk just fear mongering voodoo or real?

Also, what sample is required to perform such a test? Is jaw crusher feed OK?

How many pieces should be tested to be representative?

Alex Doll
11 months ago
Alex Doll 11 months ago

First question, short answer:  Yes, it is real.

First question, long answer:  It depends on things like crusher throw, rock hardness hardness (thus the discussion), liner and chamber geometry, and so on.  Too complicated to describe in a freebie forum like this.

Second question, find a geotechnical lab that does the test and ask them what their criteria for specimens is (it can depend on the size of their apparatus).  The ASTM standard is often used, so spend $44 and buy this:

If you have an easy source of samples, I'd say take 20-30 specimens of rock that have the required geometry described by ASTM.  The lab can shave down oversized samples, but they can't do anything with undersized ones.

9 months ago
palarfoote 9 months ago

What is the smallest setting I could adjust a 7 36 Allis Chalmers hydrocone at? I am feeding it with 1/2" chips and want to reduce it to sand (3/16") is that possible?

9 months ago

What do you mean on 3/16", P80? What capacity and ore strength?

Bill Fraser
9 months ago
Bill Fraser 9 months ago

I do not think you can on a 736.  Look at the table here. The 636 cannot. The 7 ft shorthead symons could. Maybe the 736 hydrocone could in closed circuit.

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