rathole

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rathole

[′rat‚hōl]
(mining engineering)
A shallow, small-diameter, auxiliary hole alongside the main borehole, drilled at an angle to the main hole; after core drilling is completed, the rathole is reamed out and the larger-size hole is advanced, usually by some noncoring method.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Oil-lubricated, oil-cooled gyrators induce flow and eliminate bridging and ratholing. The gyrators also reduce particle segregation to make sure each bag is completely discharged.
Problems with arching and ratholing in bins and hoppers can lead to erratic flow or complete flow stoppages.
Paddle action gently massages material down into the metering screw, eliminating ratholing and bridging, while conditioning material into a uniform bulk density.
For a funnel flow bin to operate reliably without ratholing, the outlet diameter must be greater than the critical rathole diameter, determined from appropriate shear tests (3), (4.) Limiting (worst-case) conditions for ratholing can be encountered after storage and hold periods, which are typically a part of manufacturing operations handling powder blends in bins.
If ratholing is a concern, several changes can be considered to minimize the potential.
The hopper is gently massaged from the outside by two paddles, conditioning the material to a uniform bulk density and eliminating bridging and ratholing. The feeder sits on a counterbalanced scale that weighs only the material in the feeder, not the feeder itself, to deliver maximum resolution.