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Circulating Load: Practical Mineral Processing Plant Design

Author: Robert Shoemaker
Published by Society for Mining, Metallurgy, and Exploration - 2002
56 pages

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The Circulating Load: Practical Mineral Processing Plant Design by an Old-Time Ore Dresser is loaded with innovative ideas and practical solutions to some of the most troublesome day-to-day mineral processing operational challenges. From mess-free flooring systems to inventive crusher and conveyor system designs to time-saving quality control techniques, this references is full of fresh approaches to age-old problems that can inhibit mill operating performance.

Veteran metallurgical engineer Bob Shoemaker spent his 40-year career seeking out better ways to design and manage minerals processing operations. He visited dozens of plants throughout the world and witnessed some of the industry's best ingenuity at work. He also saw his share of mistakes.

Part engineering, part common sense, this treasure trove of tips and tricks presents new and smarter ways to manage minerals processing.

Chapters include:

  • Primary Crushers
  • How to Clean Up a Dirty Dump Pocket
  • Sampling a Ball Mill
  • Vibrating Feeders
  • Notes on Conveyors
  • Storage Bins
  • The Design and Operation of Floors (From the Mill Operator's Standpoint)
  • Notes on Fines
  • Overengineering
  • Cage Mills, Impactors, and Hammer Mills
  • Environment Controls for Grinding Mills
  • That Odious Pump
  • Never Hire a Plumber Who Claims to be a Pipefitter
  • Pilot Plants
  • recious Metals Column and Heap Leaching Pilot Plants
  • Sumps, Pumps, Etc.
  • Foolproof Plug Valves
  • Design for Maintenance
  • Mexican Feeders
  • Supervising the Engineer-Constructor

REVIEW: By Doug Halbe

Bob Shoemaker has probably designed, and visited, more processing plants than any millman around…and he also took the time to write down much of what he learned. As he notes in SME’s new book The Circulating Load, “…I found that the managers and mill superintendents of …plants were most hospitable in showing me their operations and freely answered any questions I asked. During these visits I observed many clever ideas in plant design…and also many mistakes….” These ideas (and mistakes), from Bob and others in Bechtel, were collected over the years in an in-house publication “published in the interest of fewer spills in the mills.” The Circulating Load is a compilation of the best of those ideas, along with a generous helping of editorial comment by Bob Shoemaker.

Bob writes well and always to the point. What about slope on mill floors? Everyone who has hosed a spill on a flat mill floor has vowed to never allow that mistake in a new mill again but what is the proper slope? Bob has a well thought out recommendation. Which way should the slots run on floor trench grating? There’s a right way and a wrong way. How do you load fines on a conveyor belt with a vertical curve? Bob tells us how and why.

The author does have strong opinions: “The vibrating feeder…is not a feeder in the true sense of the word but is actually sometimes a vibrating, self-destroying transport device”. He is however, always fair: “There are …applications where they can be employed successfully”; and better yet, spells out what a millman or engineer needs to consider in selecting and installing this type of feeder.

The book contains suggestions for operators on simple ideas to improve operations (The leaky cyclone valve really does work) and to include in new mill design. Don’t ever design a convey system again without re-reading “Notes on Conveyors”. On the other hand, you probably only have to read once “Never Hire a Plumber Who Claims to be a Pipefitter”.

And “Storage Bins”. There’s an engineering lesson or two here, but that doesn’t interfere with a good story.

She’s deep enough.


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