Powder and Bulk Engineering
Thursday, August 21, 2014
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Powder and Bulk Engineering is a technical publication devoted to readers in the bulk solids market, worldwide.
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Publication Date: 11/1999
Pages: 6
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Safety first: Hiring a vessel cleanout service to safely unblock your silo

Have you ever had to hang from a harness inside a silo and poke rock-hard material with a pick, shovel, or other device to get the vessel contents to flow? Are your feeders covered with sledgehammer marks? Then you know material flow problems in bulk solids storage vessels can not only be unavoidable, but dangerous. Read this article for help selecting a professional vessel cleanout service that can effectively and safely get your material flowing. A related article [page 50] explains how a cleanout service handles confined-space entry.

If material has ceased to flow from your bulk storage vessel, chances are the problem is buildup, ratholing, bridging, or plugging, as shown in Figure 1. Buildup [also called hangup or wall scale] is material that clings to the vessel walls and won't flow out when the vessel is discharged, as shown in Figure 1a. The buildup's thickness can range from 1/4 inch to several feet. Ratholing, as shown in Figure 1b, is extreme buildup that leaves only a small funnel-like flow channel, called a rathole, for material to flow from the vessel top toward the outlet.

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