Drawdown Hoppers & Flow Control

The Carman Drawdown Hopper is designed for all types of outdoor storage piles. The discharger’s Projection Ring transmits vibrations throughout the pile, encouraging “slough-in”. Wet and frozen materials such as coal, potash, salt and aggregate come to life and flow from outside storage reclaim piles.

GREATER EFFICIENCY FROM VIBRATIONThe Vibratory Drawdown Hopper is located at ground

level below the stockpile, and its function is to provide

the initial flow stimulation. Once product movement

is established the flow rate is regulated by the Flow

Control Gate. Overall control is achieved by linking

a downstream belt weigher to the Flow Control Gate

operation.

This system can provide 80% more live reclaim

compared to a static hole, and is a very effective and

cost efficient method of stockpile reclaim.

STOCKPILE DISCHARGE PROBLEMSMinimal Active Reclaim:

• By utilising a static hopper and feeder, active

reclaim is limited to within approximately 40° of the

stored material’s natural angle of repose.

Bridging:

• Bridging is the archlike formation of material over

either the static hopper inlet or outlet. It results

from improperly designed hoppers or when the

outlet is too small.

Coring:

• Coring occurs when the material in the core of the

pile discharges, while material on the periphery

resists movement.

HOW THE DRAWDOWN HOPPER ELIMINATES THESE PROBLEMSMaximise 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.

Bridging Solution:

• Carman Drawdown Hoppers have command of

the material equal to the Drawdown diameter. This

results in an initial flow column equal in diameter

to the overall diameter of the Drawdown Hopper.

A highly visible flow steam also improves on-pile

equipment operator safety.

Coring Solution:

• The projection ring of the Carman Drawdown

Hopper, which is always exposed to the pile,

transmits vibration and energy directly into the

pile. This eliminates coring and maximises active

reclaim.

Drawdown Hoppers & Flow Control

Email: [email protected]


FLOW CONTROL METHODSVibrating feeder:

• The Drawdown Hopper and vibrating feeder has

been used for many years and has proven a reliable

method to reclaim material from a stockpile. The

vibrating feeder is well suited to handle small to

moderate flow rates.

“Swing hopper” Flow Control Gate:

• With the requirement for larger reclaim rates

other systems were developed. The Halley &

Mellowes “Swing Hopper” Flow Control Gate was

designed to enable large flow rates up to 6,000

tonnes per hour (coal) to be controlled. With only

one moving component, this system will allow

variable discharge rates by position adjustment of

a pivoted swing hopper against a stationary curved

floor. When adjusting the swing hopper away

from curved floor, an open area is created to allow

material flow. The volume of material discharged

varies depending on gate position. This system

has been installed in a large number of locations

in Australia and overseas, and has been operating

reliably for more than 20 years.

Low Headroom Flow Control Gate:

• The latest development to regulate material flow is

the Low Headroom Flow Control Gate. This gate

is a heavy-duty bi-parting slide gate designed by

Picor (US), and it incorporates a range of unique

design features. It was introduced in Australia a

few years ago by Halley & Mellowes in response to

a call for lower headroom in reclaim tunnels. This

new Low Headroom Flow Control Gate has been

installed in a number of recent Australian projects

and is performing reliably as it has done overseas

for many years.

The benefits of this gate:

• Reduced reclaim chamber head height (by over

2 metres). This reduces excavation and concrete

structure costs.

• Reduced capital cost by 50%

• Non-stop infinite modulating control. Hydraulic

power source allows instant flow rate change in

response to weigh scale signals.

• Easy low maintenance (no rollers). This gate uses

low friction HD polymer blocks with long lifespan.

• Fail-safe close. Hydraulic accumulator immediately

closes the Flow Control Gate in the event of power

failure, ready for restart.



APPLICATIONSProblem:

• An ore mine was experiencing periodic shutdowns

due to an inadequate method of handling

mine tailings. Constant attention and excessive

manpower was required to permanently dispose of

refuse.

The Solution:

• A waste system was installed which included

10 Carman Drawdown Hoppers with reclaim

capability of 14,500 tons. The Drawdown Hoppers

feed a conveyor system leading to a permanent

refuse facility. Shutdowns have been replaced by

immediate, uninterrupted flow of refuse material.

Problem:

• An lowa power company required a reliable active

reclaim system which would insure positive flow to

fuel preparation equipment.

The Solution:

• Application data was analysed 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, bulldozerproof

installation.

Problem:

• A cogeneration facility in North Carolina required

maximum reclaim and equipment reliability in the

reclamation of coal for boilers.

The Solution:

• Carman recommended two Drawdown Hoppers

located in each side of two stacking tubes. Field

tests conducted by the customer report the reclaim

achieved is nearly identical to that predicted.

60 Degree Cone Design:

• After testing many cone configurations, our 60

degree design has proven to be the most effective

for Drawdown Hopper performance. Its 60 degree

cone promotes steady flow eliminates dormant area

associated with other configurations.

Installation Ease:

• No other reclaim device installs as easily as a

Carman Drawdown Hopper – we guarantee it. Our

units come absolutely complete, ready to install. All

you supply is the crane. Premounted isolators and

installation hardware are provided.

Cycled Operation:

• Carman’s unique design permits cycling of the unit

to achieve maximum reclaim. Cycling produces

uniform flow, longer exciter life and reduced power

consumption.

MAT-DS-0009 - FEB 2018


Drawdown Hoppers & Flow Control

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