Product Profile

Carman Drawdown Hoppers eliminate outdoor stockpile storage and reclaim problems including Coring, Bridging, and Minimal Active Reclaim by using vibratory action to transmit energy directly into the stockpile, encouraging sloughing into the flow stream and maximizing active reclaim.

Carman Drawdown Hoppers feature a projection ring to transmit vibration and energy directly into a storage pile.

Typical rathole (top) and Carman Drawdown Hopper (bottom).

Individually engineered for each application, the unique design of the Carman Drawdown Hopper allows easy installation with the ruggedness to stay on-line.

To ensure proper application, Carman engineers carefully analyze the flow properties of your product or raw material in our laboratory and by using our exclusive computer analysis program.

Outdoor Storage Problems

Outdoor storage problems, including coring and bridging are usually related to compaction resulting from one or more of the following conditions:


Coring occurs when the material in the core of the pile discharges, while material on the periphery resists movement.


Bridging is the arch-like formation of material over either the static hopper inlet or outlet. It results from improperly designed hoppers or when the outlet is too small. Bridging also masks the location of the flow stream, a potentially dangerous condition for on-pile equipment operators.

Minimal Active Reclaim

By utilizing a static hopper and feeder, active reclaim is limited to within approximately 40 degrees of the stored material's natural angle of repose.

Carman Drawdown Hopper Solutions

A properly sized Carman Drawdown Hopper can economically eliminate outdoor storage problems.

Eliminate Coring

The projection ring of the Carman Drawdown Hopper, which is always exposed to the pile, transmits vibration and energy directly into the pile. As the central column of flow is drawn down, fracture lines encourage sloughing into the flow stream, eliminating coring.

Eliminate Bridging

Carman Drawdown Hoppers have command of the material equal to the Drawdown diameter. This results in an initial flow column equal to the inside diameter of the projection ring. A highly visible flow stream also improves on-pile equipment operator safety.

Maximize Active Reclaim

Carman Drawdown Hoppers consistently increase active reclaim to within 5 to 10 degrees of a material's natural angle of repose. A Carman Drawdown Hopper can provide 4 to 5 times the reclaim of an equally sized static hopper with a feeder.

Case Histories


A Midwest power company experienced serious reclaim problems when handling fine eastern coal. The existing static hopper produced nothing more than a rathole and required continuous bulldozer attention which resulted in compaction. Bulldozer operator safety was another concern.

The Carman Solution:

A model 8GDH Drawdown Hopper was installed on a steel structure and concrete pad that replaced the static hopper. With only minor modifications, the existing gate and belt feeder were reused. When handling fine coal, reclaim is equal to that predicted with little bulldozer activity.


An Iowa power company required a reliable active reclaim system which would insure positive flow to fuel preparation equipment.

The Carman Solution:

Application data was analyzed and four Drawdown Hoppers, symmetrically placed around the stacking tower provide a positive and continuous material source for feeders located in the tunnel. The concrete pads provide a flush, bulldozer-proof installation.


A cogeneration facility in North Carolina required maximum reclaim and equipment reliability in the reclamation of coal for boilers.

The Carman Solution:

Carman recommended two Drawdown Hoppers located on each side of two stacking tubes. Field tests conducted by the customer report the reclaim achieved is nearly identical to that predicted.


A major southern utility required a system for reclaiming stored coal including western sub-bituminous. Various grades of coal were then to be blended at specified rates to satisfy boiler demand and air quality regulations.

The Carman Solution:

Telescoping chutes control dust while distributing graded coal over fourteen (14) Carman Drawdowns strategically located to maximize reclaim. Self-contained adjustable rate vibrating feeders under each drawdown maintain blend specifications while satisfying boiler fuel requirements.

800-456-7560 | 812-288-4708 FAX | | ęCarman Industries 2009

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