Drawdown Hoppers |
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.
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Greater Efficiency from Vibration
The 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. |
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| Discharge Problems |
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Minimal 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. |
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| How the Drawdown Hopper eliminates these problems |
Maximise 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. |
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Vibrating 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
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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.
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| Advantages of our Drawdown Hopper |
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1 - Projection Ring:
Carman’s unique Projection Ring is
always in contact with the storage
pile. Better flow stimulation and high reclaim percentages result from the controlled transmission of vibratory energy. |
2 - Complete Range of Construction Materials and Liners:
Carman provides a complete range of construction materials and liner choices, including various grades of stainless steel, abrasion resistant steel, epoxy and urethane. Whether your application is coal, wood, fertiliser, salt, iron ore, tailings or something else Carman can supply the proper construction materials. |
3 - Drive Motor:
Carman’s Drawdowm Hopper has separate electrical and mechanical drive components for reliability and ease of maintenance. A standard 1800rpm, TEFC foot-mounted motor transmits power though a belt drive to the centrifugal force exciter. |
4 - Patented Rubber Isolators:
Carman’s patented isolators system was developed to support the enormous loads encountered under a storage pile. Specifically designed for use with Drawdown Hoppers, molded rubber isolators are totally non-restraining to allow more motion more flow stimulation, less power consumption and maximum reclaim. The chamfered top of each isolator allows improved isolation under all conditions from full to no-load.
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5 - Centifugal Force Exciter:
The low frequency, long stroke action of the force exciter generates the high energy required for maximum reclaim. Carman’s centrifugal force exciter consists of adjustable eccentric weight mounted on a single shaft and supported by bearings. Grease lubricated double roll spherical bearings assure long life. The exciter is easily accessible for
maintenance and serviceability. |
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| Applications |
Problem:
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. |
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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. |
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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. |
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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. |
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