The Safe Working Practice of Changing Out a Raisebore

Report
The Safe Working Practice of
Changing Out a Raisebore
Reaming Head Underground
Eloise Copper Mine
Overview of Operation
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Eloise Mine Site.
Underground Operation – mining ~
500,000t/annum – 70,000t/annum Cu Con.
Currently 570m underground.
Main Orebodies – Levuka and Elrose.
Levuka South – offset by main faulting structure.
Necessary to install new ventilation shaft to
supply adequate ventilation to this area.
Overview of Ventilation Shaft
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Ventilation shaft established through collaboration of
the following contractors.
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Major Pontil.
Raisebore Australia.
Townsville engineering.
Jetcrete.
EROC (formally Peabody mining services).
Piling contractors.
Nortask.
Australian mining consultants (AMC).
Hard rock electrical.
Supervision and design Amalg resources.
Development of Ventilation Shaft
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Begun 20th July
Major Pontil – 482.5m directional hole accurate within
0.35m
Hole reamed to accommodate RBA drill string
RBA back reamed 3.5m diameter shaft up to the
cretaceous sediments (overburden)
Lower rods – will expand upon this step
Changed to 660mm diameter head – reamed to
surface
Piling contractors and Jetcrete worked together to
bore and line the remaining 57m to a diameter of 3.0m
Installation of the southern ventilation fan
As a note increased the quanity of air from 82m3/s to
197m3/s
Completed 22nd December
The PROBLEM
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Risk assessment conducted on all identifiable
sections of the project.
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Significant risk associated with the servicing of the
raisebore cutter head.
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Needed to completely isolate the area around the
bottom of the reamed shaft – Identified 3m as being a
safe working distance after risk assessment
conducted.
The SOLUTION
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Planned for at least one change out.
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Decision between AMALG Res. and RBA was to
design and fabricate an extended pair of breakout
spanners.
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Drawings were completed sent to AMALG’s
Mechanical engineer to perform strength of material
calculation’s.
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These were then sent to Townsville Engineering for
fabrication.
Super Spanner
SPECIFICATIONS
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Spanners constructed of:
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Bisalloy 80
50mm thick
Built up around jaws of spanner
Top spanner 3.85m
Bottom spanner 4.1m
– Arguably the biggest spanners in North
Queensland
Close up of top spanner
The CONCEPT
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Top spanner wraps around stabilizing rod inside ribs.
Bottom spanner sits below it and offset from it.
Portapower ram links the two spanners via a rod.
Ram extended forcing spanners together.
Force supplied sufficient to overcome the torque
applied when initially tensioning rods.
Joint between stem rod and stabilizer loosened.
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Simply rotate drill string anti clockwise to remove
reaming head.
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Result – removal of reaming head without personnel
being exposed to shaft brow.
The PROCESS
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Operators briefed and JSA agreed upon and signed off.
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Establish communications between surface drill rig
operator and underground operators.
Lower rods to floor.
Forklift hooks up conventional spanner.
Rotate rods so spanner on right hand side of drive.
Forklift hooks up second wrap around spanner.
Link two spanners with rod and portapower ram.
Apply pressure to portapower to loosen raisebore head
from stabilizer rod.
Spanners removed.
Stem rod and reaming head removed.
Raisebore head dragged out with loader.
Connect 660mm raisebore head.
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PHOTO 1
PHOTO 2
PHOTO 3
The COST ALTERNATIVES
Alternative 1 Alternative 2
Spanners
Delay Rates ($350/hr)
Replacement Stabilizer Rod
Time to Complete (hrs)
Total Cost
$11,124
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$875
$42,000
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$15,000
2.5
120
$11,999
$57,000
*Note The spanners were available at the completion of the project. Sold to RBA at cost
The RESULT
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Alternative 1 was chosen
 Completed ahead of time and under budget
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Safe, economical and timely solution to a common
problem
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The result proved that INNOVATIONS such as this can
be implemented if a little thought goes into the initial
design stages

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