Ask an Expert

Q: We have a plant in another country that manufactures the same product that we make here in the U.S. We each qualify our product by a sieve analysis of the finished blend. The foreign plant buys their sieves locally. Can I be sure that they are using the same mesh sieves that I am using?

James Davis, Powder Processing Solutions, says: The key is understanding what sieve sizes mean so your domestic and foreign plants can be in sync. Mesh sizes were developed by the W. S. Tyler screening company to more easily qualify screen sizes. The mesh number refers to the number of openings per lineal inch of screen cloth. For example, a Tyler 32 had 32 openings per lineal inch.

In some cases, the Tyler number was hard to remember. For mesh sizes from 20 to 60, the Tyler numbers are 20, 24, 28, 32, 35, 42, 48, and 60, corresponding to the number of openings per inch. By comparison, the more universally accepted US Standard Sieve sizes (which are arbitrary and not tied to the number of openings) are 20, 25, 30, 35, 40, 45, 50, and 60. It is easier to remember sieves organized by units of 5 and 10. The micron sizes of the openings for both are:

Incidentally, each sieve is the fourth root of 2 smaller than the sieve above. So, 841 divided by the fourth root of 2 is 707, 707 divided by the fourth root of 2 is 595, and so on. A common practice for creating a sieve stack for a broad particle size range is to use the square root of two for each successively smaller sieve; mathematically, this works out to every other sieve. A common sieve stack might include 20, 30, 40, 50, and 70 in the U.S. Standard numbers. This is much easier to remember than the real openings per inch of the Tyler numbers, which are 20, 28, 35, 48, and 65.
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James Davis is president of Powder Processing Solutions and a member of PBE's Editorial Advisory Board. To contact him, send an e-mail to jimdavispe@gmail.com.

Editor’s note: To send your comments or questions about this or other issues related to handling and processing dry bulk solids, send an e-mail to holly@cscpub.com.

Feature

Plant owners and workers alike prefer to avoid having workplace dust. A dusty plant increases housekeeping duties. It can be a health hazard for workers or simply irritate them by requiring them to use bulky personal protection equipment. A dusty workplace can also be dangerous if the powder is explosive. To minimize these problems, plant owners install dust collection systems that remove fines from separation equipment and capture nuisance dust at various process points.

But what happens to the collected fines and dust? Reusing this fine powder can be difficult because its small particle size tends to make it cohesive. Like some plants, your plant may simply discard the powder as a waste stream, perhaps paying to landfill it. Or your plant may put the fine powder back into the process, with the result that segregation problems develop in your downstream equipment. Maybe your plant simply mixes it with the final product stream, hoping customers won't reject the lower-grade product that this sometimes produces.

Even a small amount of waste fines and dust can mean significant financial losses for your overall process. For instance, if your process runs at 60 t/h 24 hours a day, 7 days a week, and has a waste material stream that represents a 0.5 percent loss in product yield, you're discarding more than 2,600 t/y of material. This is equivalent to losing 36 hours of full production each year. To turn these losses into gains, turn to agglomeration. This process, which turns fine waste powders into larger, easier-to-handle agglomerates, can be defined as "particle size enlargement in which small, fine particles, such as dusts or powders, are gathered into larger masses, clusters, pellets, or briquets for use in products or in a secondary processing step." Agglomeration for fine waste powders is commonly achieved by compression or mechanical mixing.
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Read It Here First

Stanco Projects, a division of Semco Systems Ltd., Richmond, British Columbia, designs, manufactures, and installs a wide range of turnkey bulk chemical handling systems for power, mining, and petrochemical facilities around the world. The company frequently installs chemical slurry makeup systems for produced water treatment at oil and gas facilities in northern Canada.

A typical system consists of a storage tank with an upper storage section topped by a dust collector and a lower skirted section that holds ancillary equipment, including a slide gate, screw feeder, slurry mixer, slurry pump, and other controls and components. For many of the company's projects, the tank can be up to 14 feet in diameter and up to 100 feet tall.

In the past, the company typically purchased shop-welded steel tanks from one supplier and the other equipment from other suppliers and shipped these various system components to the installation site. An on-site assembly crew erected the tank by crane and installed the ancillary equipment inside the tank's lower skirt section. However, this was an expensive and time-consuming process that generally took about 4 weeks to complete. Faraway, isolated job sites meant higher freight costs, worker transport costs, and overtime expenses, not to mention difficult working conditions.

The company tried to reduce the cost of some projects by using local contractors to install the systems, but found that when it could find qualified contractors in such remote locations, they usually cost more. And the company was installing more systems at facilities in increasingly remote locations.

To learn how the company worked with a tank supplier to decrease the time and work required to install a system, you can read "A better storage tank system," in the November issue of Powder and Bulk Engineering. To read it today, click here.

International

Global zirconium concentrate production drops
Production difficulties in Australia, Indonesia, and Mozambique contributed to a 5 percent global decrease in zirconium concentrate production in 2008. A report from MarketPublishers, a publisher of market research reports in Birmingham, U.K., "Zirconium Oxide (CAS 1314-23-4) Market Research Report 2009," also noted that the more limited supply led to significant price increases for zirconium concentrates.

For more information, go to www.marketpublishers.com.

Industry News

US rigid bulk packaging demand to reach $7.0 billion by 2013
US demand for rigid bulk packaging is expected to increase 2.1 percent annually to reach $7.0 billion in 2013, according to "Rigid Bulk Packaging," a study from industrial market research firm The Freedonia Group Inc. Gains will be bolstered by an improvement in real manufacturing activity as well as a shift toward larger, higher-value containers that offer enhanced performance and cost effectiveness.

Demand will be aided by the ongoing need for containers that comply with various regulations. Rigid intermediate bulk containers will register the fastest gains, with demand increasing 4.2 percent annually to $890 million in 2013. Material handling containers will also see above-average growth, supported by a shift to reusable bulk containers. Drum demand will advance less than 1 percent annually to $2.2 billion in 2013.

The study is available from The Freedonia Group (pr@freedoniagroup.com, www.freedoniagroup.com).


Supplier News

Renold Americas names new president
Rick Hamilton has been named President of Renold Americas, effective immediately. He will be responsible for all sales operations in the United States, Canada, and Latin America. www.renold.com


Company offers free safety brochure on X-ray systems for contaminant detection
Eriez Magnetics is offering a free PDF that answers frequently asked questions about cabinet x-ray inspection systems. eriez.com/products/xray.

Beumer designs award-winning automated packaging system
Beumer Corporation developed an automated packaging system that won the PMT Packaging Line of the Year Award for Barry Callebaut LLC's Eddystone, Pa., facility. http://www.pmmi.org/a/article.asp?id=2423.

Events

Innovations in Food Processing, November 4, at the Embassy Suites Hotel Dallas in Irving, Texas. Sponsored by K-Tron Process Group, Sweco, Quadro Engineering, Eriez, and Matcon. Course covers screening and sieving, material handling and conveying, ingredient feeding, mixing, pneumatic conveying, contaminant removal, and milling. Contact K-Tron at 856-589-0500, fax 856-582-7968 (www.ktron.com/seminars).

Feeders: Don't Overlook the Basics, Webinar, November 10, 2009, 2:00 EST. Sponsored by PBE. Presenter Eric P. Maynard, Jenike & Johanson, will discuss fundamental principles involved in selecting an effective bulk solids feeder and special feeding applications, like micro-feeding. Click here to register.

Continuing Education

Powder Flow 2009: Practice, Theory, Visualisation and Meaning, December 16 at the RSC, Burlington House, London. Sponsored by The Formulation Group. Course covers the practice of powder flow measurement, visualisation of powder flow, and theory and its physical meaning to understand particulate flows. Contact The Formulation Group at info@powderflow.com ( www.powderflow.com).