Statistical Methods For: Mineral Engineers

Then she closed her laptop, patted Montgomery’s textbook, and smiled. Statistics didn't move rock. But they told you which lever to pull, and when to leave it alone. That was the real art of mineral engineering.

“Here to fix what ain’t broke, Doc?” he grunted. Statistical Methods For Mineral Engineers

“For the last six hours,” she said, pointing to a string of seven points all below the centerline, “we have been running fine. But this run of seven points all below the mean? That’s a Nelson Rule violation. It’s not out of control statistically, but the probability of this happening by chance is less than 1%. It’s a trend. The mill is grinding finer because the new media supplier’s ball hardness is different. We need to back off the feed rate now—not in two hours.” Then she closed her laptop, patted Montgomery’s textbook,

She left him with a process behavior chart and walked to the grinding mill. That was the real art of mineral engineering

Her first stop was the primary crusher. The operator, a veteran named Gus who chewed tobacco and hated change, saw her coming.

She drew a Shewhart control chart on a whiteboard in the control room. Upper control limit. Lower control limit. And in the center, the target P80 of 150 microns.

The average was just a ghost. The plant was either choking or starving, never steady.