CRO Test Module 2 Questions & Answers 2024/2025
If the first chamber of a horizontal ball mill is performing well, what is the maximum size necessary in the second chamber? - ANSWERS30 mm
True or False: It is recommended to release and recharge grinding media charge only once a year. - ANSW...
If the first chamber of a horizontal ball mill is performing well, what is the maximum size necessary in the
second chamber? - ANSWERS30 mm
True or False: It is recommended to release and recharge grinding media charge only once a year. -
ANSWERSTrue
What is the benefit/purpose of injecting grinding aids? - ANSWERSa) Allow for the use of finer grinding
media in second chamber
b) Eliminate particle polarity that causes material agglomeration
c) Improve separator efficiency
What is the main reason why finished cement needs to meet a certain blaine target, why is this fineness
so important? - ANSWERSTo have enough surface area to react with water properly during cement
hydration (leading to proper strength development and setting time).
Having a grit separator in circuit with an end discharge ball mill contributes to a (increase OR decrease)
in venting air velocity. - ANSWERSIncrease
Why is temperature control so critical in a cement grinding system? - ANSWERSTo properly control the
dehydration of gypsum in the mix.
What is the critical speed of a ball mill? - ANSWERSThe speed where the media begins completely
centrifuging and spins with the walls of the mill without tumbling (lowest grinding efficiency)
True or False: The most effective method of cooling water injection in ball mill is co-current (same
direction) with the ventilation air flow through the mill. - ANSWERSTrue
, The ideal speed for most mills is around _____% of critical speed? - ANSWERS70-85%
Which is the most widely used grinding equipment in the cement manufacturing industry for cement
milling? - ANSWERSBall Mill
What is the recommended Cement exit temperature from the mill? - ANSWERS110 - 115 deg C (230 -
239 F)
What is the intended purpose of gypsum in cement performance? - ANSWERSTo slow the setting time of
cement during hydration.
What compound does the SO4 from gypsum react with to slow setting time? - ANSWERSC3A
What factors determines the power consumption of a mill? - ANSWERSTons of grinding media, mill
speed, mill size (diameter)
What is meant by volume loading inside the mill? - ANSWERSPercentage volume grinding media
occupies in a chamber.
What is max recommended value for mill volume loading degree? - ANSWERS33%
What could be happening inside the HBM if main motor amps are increasing and elevator amps are
increasing suddenly? - ANSWERSMill is suddenly flushing (could be grinding aid/water suddenly added),
break through caking/plugging in the diaphragm
What could be happening inside the HBM if main motor amps are dropping and elevator amps are
dropping? - ANSWERSMaterial being retained inside the mill (loss of grinding aid/water, plugging of the
diaphragm, etc.)
What could be happening if the product from HBM system is too coarse? - ANSWERSToo coarse --- Not
grinding adequately or over drafting. Diaphragm slots too big or worn. Separator efficiency dropped
(vanes are worn or speed reduced).
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