Gearless Mill Drives - Cbmua.org

2009 

Gearless Mill Drives 

Machinery Risk Solutions 

Practice 

Matt Dugalic P.Eng., MARSH – MRSP Risk Consultant, VP 

Kurt Tischler Dipl.-Ing., Siemens – Product Manager, Mining 

www.marsh.ca www.marsh.com

WHY shift to the gearless drives in mineral processing ??? 

� Mill size – grinding economies of scale 

� Relative lifecycle cost 

� Lower power consumption 

� Robust design 

� Avoiding critical open gear power trains 

� Variable speed 

� Compatibility with processing plants 

� Engineering design efficiencies 

� Availability 

� Minimal downtime 

Marsh 

1

Marsh 

However, 

from the machinery breakdown 

underwriting perspective, this 

often creates a 

critical, single point exposure !!! 

2

Significant Mining Industry Property Losses (Jan 2006 – Jul 2009) 

Class Loss Type Gross Claim 

Marsh 

(MM US$) 

Coal Flood +/- 603 



Iron Storm / Flooding +/- 180 

Manganese Smelter Explosion +/- 170 

Platinum Flood +/- 140.3 

Iron / Salt Typhoon (Glenda) +/- 122.4 

Copper & Zinc Electrical Flashovers of SAG Mill Stator +/- 115 

Iron / Salt Typhoon (Emma) +/- 107.7 

. . . 

Siemens 

3

www.marsh.ca www.marsh.com

SIMINE Mill Gearless Drive 

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Siemens’ Gearless Drive Technology 

Performance 

Facts & Figures 

Confidential / Copyright © Siemens AG 2009


Performance 

Content 

� Experience & References (5 minutes) 

� Maintenance, Service (2 minutes) 

� Major Problems and their Solutions (25 minutes) 

Cadia, Repairs, Lessons learned 

Chilean plant, Rotor failure 

� Performance: Downtime; Availability (10 minutes) 

Page 2 October 2009 Kurt Tischler 

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Experience First Gearless Drive in Mining 

Sydvaranger Norway 

Gearless Drive 8200 kW 

for a Ballmill 

of 21.3 ft ID 

Start-up: 

1980 


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Experience 




of 21.3 ft ID 

Start-up: 

1980 

History: 

1997: Shutdown of plant 

due to low iron prices 

2005: 

Mill and Gearless Drive 

sold to Zinifex Australia 


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Experience 




of 21.3 ft ID 

Start-up: 

1980 

History: 

1997: Shutdown of plant 

due to low iron prices 

2005: 

Mill and Gearless Drive 

sold to Zinifex Australia 

2008: Restart in Zinifex’ 

Century Zinc Plant 


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CODELCO Chuquicamata, 2 GD 8210kW, 32’ 

First SAG-Mill Gearless Drives 

Start-up: 

1988 

Altitude: 

3000 m 


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CODELCO El Teniente, GD 12000 kW 

First 36’ SAG-Mill Gearless Drive 

Start-up: 

1991 


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Freeport II; Indonesia, 20400 kW 

First 38’ SAG-Mill Gearless Drive 

Start-up: 

1997 

Altitude: 

2700 m 


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Cadia Australia, GD 20000 kW, 

First 40’ SAG-Mill Gearless Drives 

Start-up: 

1998 


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References 

Plant 

SYDVARANGER 

CHUQUICAMATA 1 

CHUQUICAMATA 2 

EL TENIENTE 

GOLDFIELDS 1 

GOLDFIELDS 2 

KENNECOTT 

NORILSK NICKEL 1 

NORILSK NICKEL 2 

CANDELARIA 1 

FREEPORT 1 

ALUMBRERA 1 

ALUMBRERA 2 

FREEPORT 2 

CANDELARIA 2 

CADIA 

ANDINA 

OLYMPIC DAM 

PELAMBRES 1 

PELAMBRES 2 

20 Gearless Drives 

Country 

Norway 

Chile 

Chile 

Chile 

South Africa 

South Africa 

USA 

Russia 

Russia 

Chile 

Indonesia 

Argentina 

Argentina 

Indonesia 

Chile 

Australia 

Chile 

Australia 

Chile 

Chile 

Type of Mill 

Ball-Mill 

SAG-Mill 



AG-Mill 
















ID of Mill (ft) 

Total Power 

233,542 


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Confidential / Copyright © Siemens AG 2009 

21.3 

32 

32 

36 

16.4 

16.4 

36 

21.3 

21.3 

36 

34 

36 

36 

38 

36 

40 

36 

38 

36 

36 

Rated Power (kW) Start-up 

8,200 

8,210 

8,210 

11,200 

4,000 

4,000 

12,000 

9,650 

9,650 

12,000 

10,600 

13,400 

13,400 

20,400 

12,000 

20,000 

12,000 

18,000 

13,311 

13,311 

1980 

1988 

1989 

1990 

1990 

1990 

1991 

1991 

1991 

1993 

1995 

1997 

1997 

1997 

1997 

1998 

1998 

1998 

1999 

1999 

kW


References 

Plant 

20 above 

SAN CRISTOBAL 

SAN CRISTOBAL 

SAN CRISTOBAL 

EL TENIENTE 

EL TENIENTE 

EL TENIENTE 

EL TENIENTE 

Barrick Cowal 

Barrick Cowal 

Equinox Lumwana 

Equinox Lumwana 

RPM Kinross 

Peñasquito 

Peñasquito 

Los Pelambres 

Los Pelambres 

Las Brisas 

Las Brisas 

ANGLO Los Bronces 


Country 

Bolivia 

Bolivia 

Bolivia 

Chile 

Chile 

Chile 

Chile 

Australia 

Australia 

Zambia 

Zambia 

Brazil 

México 

México 

Chile 

Chile 

Venezuela 

Venezuela 

Chile 

















Ballmill 





Total Power 

520,310 

Scheduled 2011 


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36 

22 

22 

38 

24 

24 

24 

36 

22 

38 

26 

38 

38 

38 

36 

26 

38 

38 

40 


233,542 

13,050 

7,830 

7,830 

19,400 

11,186 

11,186 

11,186 

12,500 

10,500 

18,000 

15,000 

20,000 

18,300 

18,300 

15,000 

15,500 

20,000 

20,000 

22,000 

2007 

2007 

2007 

2003 

2003 

2003 

2006 

2006 

2006 

2008 

2008 

2008 





Project stopped 


kW


References 

Plant 

39 above 

ANGLO Los Bronces 

CP –Mining 

CP –Mining 

CP –Mining 

CP –Mining 

CP –Mining 

CP –Mining 

CP –Mining 

Xstrata Las Bambas 



Aurox Balla Balla 

Aurox Balla Balla 

Antamina 

Antamina 

Escondida 

Escondida 

Escondida 

Escondida 


Country 

Chile 

Australia 

Australia 

Australia 

Australia 

Australia 

Australia 

Australia 

Peru 

Peru 

Peru 

Australia 

Australia 

Peru 

Peru 

Chile 

Chile 

Chile 

Chile 











Ballmill 

Ballmill 


Ballmill 


Ballmill 


Ballmill 

Ballmill 

Ballmill 




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26 

40 

40 

40 

40 

40 

40 

40 

40 

26 

26 

34 

26 

38 

24 

40 

26 

26 

26 

Total Power 


520,310 above 

16,400 

28,000 

28,000 

28,000 

28,000 

28,000 

28,000 

28,000 

24,000 

16,400 

16,400 

14,000 

17,000 

20,142 

11,190 

22,000 

15,700 

15,700 

15,700 

892,942 



















kW

Plant 

SIMINE CIS Mill gearless drives 

References 

58 above 

Escondida 

Escondida 

Escondida 

Xstrata 2 

Xstrata 2 

Xstrata 2 


Country 

Chile 

Chile 

Chile 

Peru or Chile 

Peru or Chile 

Peru or Chile 


Ballmill 

Ballmill 

Ballmill 


Ballmill 

Ballmill 


in operation: 33 

in fabrication or installation: 21 

project stopped: 4 

order cancelled: 6 



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26 

26 

26 

40 

26 

26 

Total Power 


892,942 above 

15,700 

15,700 

15,700 

24,000 

16,400 

16,400 

1’003,920 






kW


Clarification 

No flashovers in Siemens’ SAG-Mill Stators 


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Clarification 

Collahuasi Chile: 40’ Gearless Mill Drive NOT Siemens supply 

Escondida Chile: 38’ Gearless Mill Drive NOT Siemens supply 

Escondida Chile: 25’ Gearless Mill Drives NOT Siemens supply 

Antamina Peru: 38’ Gearless Mill Drive NOT Siemens supply 

Antamina Peru: 24’ Gearless Mill Drives NOT Siemens supply 


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10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

SIMINE Mill GD 

Experience 

Number 

11 

Goldfields 

Ball-Mills SAG-Mills 

Antamina 

El 

Kolskaya San Teniente 

Cristobal 

Syd- Cowal 

varanger 

Xstrada 2 

Antapaccay 

Pelambres 

Los Bronces 

Lumwana 

Pelambres 

San Cristobal 

Cowal 

Pelambres 

Andina 

Alumbrera 

Candelaria 

Kennecott 

El Teniente 

Chuquicamata 

Balla Balla 

Freeport 

Antamina 

Las Brisas 

Paracatu 

Peñasquito 

Lumwana 

El Teniente 

Olympic Dam 

Freeport 

16’ 21’ 22’ 24’ 26’ 

32’ 34’ 36’ 38’ 40’ 

Xstrada 2 

Antapaccay 

CP-Mining 

Los Bronces 

Cadia 


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Mill 

Diameter


Experience 

Total Operation hours 

SIMINE Mill GD in Mining: 

307 

Machine years 

until September 2009 


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Experience 



105,000 

Machine days 



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Performance 

Content 






Performance: Downtime; Availability (10 minutes) 


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Maintenance, Service 

Preventive Maintenance of Gearless 

Drive is performed during downtime 

for Mill Maintenance 

No additional downtime for preventive 

Maintenance of Gearless Drive 


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Recommended Maintenance Schedule 


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Recommended Maintenance Schedule 

Preventive maintenance recommended 

� Four (4) actions (in total 13 minutes) once per month, during operation, 

� Eleven (11) actions (in total 247 minutes) once per 3 months, during operation, 

� Two (2) actions (in total 130 minutes) once per 6 months, 

during downtime for maintenance of mill, 

� 27 actions (in total 25 hours and 46 minutes) once per year, 


� Five (5) actions (in total 8 hours) once per 3 years, 


� Five (5) actions (in total 9 hours) once per 5 years, 



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Maintenance, Service 

� Minimum work for maintenance of Gearless Drive, 

average of 37 hours per year, 

� Normal electricians and engineers are requested for scheduled 

maintenance, 

�Siemens offers maintenance and service contracts 


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Performance 

Content 








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Cadia; Australia 

Gearless Drive 20 000 kW for a 40 ft. SAG-Mill 

Observed Phenomena 

at the Motor of Cadia 

Commissioning in 

May 1998 

Elastic Deflections 

During Startup 

Vibrations 

during operation 


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Cadia: Investigation 

P [MW] 

20 

10 

0 

Resonance frequency of the stator system 

Operating 

range ran range ge 

7 Hz = 9.5 rpm 

Rated speed: 9.01 rpm 

Rated frequency: 6.6 Hz 

Maximum speed: 10.36 rpm 

Max. frequency: 7.6 Hz 

0 1 2 3 4 5 6 7 8 9 10 11 12 

f [Hz] 


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Cadia: 

Resonance of the stator system 

The resonance already appeared during commissioning in July 1998 

The problems occurred at cold 

condition of the motor. 

Reaching the operation temperature 

of the Ring motor the vibrations 

disappeared 

and the Gearless Drive was operated 

using the complete speed range 


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Cadia: Resonance of the stator system; 

PRELIMINARY MEASURES 

During commissioning stage Siemens provided preliminary measures to 

enable the operation of Gearless Drive and SAG-Mill also at cold condition. 

Pedestals with hydraulic jacks were installed at 

the stator bottom to increase stiffness of stator. 


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PRELIMINARY MEASURES 

The preliminary measures allowed the operation in the complete speed range 

also in cold condition. 

The preliminary measures were so successful that Cadia 

operated the SAG-Mill continuously at full throughput. 

As a consequence Cadia allowed 

access for investigation 

only during liner change, 

six months after start of 

commercial operation. 


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INVESTIGATION 

During liner change was performed the deflection measurement taken on 

the motor of Cadia with photogrammetric system 


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Cadia: Lessons learned 

Improved FE model, considering non-linear air gap behavior 

� Special airgap elements 

allow a direct input of 

excitation current 

� Reaction forces are 

calculated on deformed 

structure 

� Dynamic reaction of 

structure is calculated 

with direct time integration 

Foundation 

stiffness 

Stator modeled 

with beam 

elements 

Mill 

stiffness 

Mill modeled 

as rigid body 

on springs 

Air gap 

elements 

Non-linear air gap force 

vs. deflection 

relation 


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3 rd mode shape: 

Ovalization 


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4 th mode shape: 

Twisting 


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Cadia: Repairs 

Modification of stator 

Modified form of the stator 

Additional stiffener built 

on the stator 


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End of 1999 the stiffener was installed on the stator 

The installation of the 

stiffener was performed 

during a 

downtime of 7 days 

parallel to a liner change of 

five days. 


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Final solution: Stator with stiffener 

Since installation of the stiffener, end of 1999, the Ring motor of Cadia 

does not show any vibrations any more. 


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Cadia: Rotor Pole Segments 

Cracks at support ribs 

Rotor poles 

Lamination core 

Rotor support 

Rotor flange 

Mill flange 


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Cracks at support ribs 

Change of airgap at several 

spots was detected in 2003. 

The problem was investigated 

during liner change. 

Engineering analysis and repair 

concept was developed by 

Siemens together with Cadia and 

EAnD. 

Cadia published a paper on the SAG-conference 2006 in Vancouver. 

Please find more details there. 


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Repair 

Repair was performed during a scheduled downtime of 15 days in 

June 2005 in parallel to a liner change, which normally needs four 

days. 


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Cadia Gearless Drive 

AVAILABILITY 

Start-up July 1998 to 2003 mechanical & electrical: 98.5 % 

From 2003 to 2005 electrical: 98.5 % 

2005 Repair of rotor electrical: 95.5 % 

2005 to date electrical: higher than 99 % 

Ring motor: 100 % 


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Cadia: Cracks of welding beams at rotor support 

Design Change 

Lamination 

Weld 

Pressure plate 

Flange plate 

Pressure bolt 

Divided rib 


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Design Change 

Magnetic pull 

Magnetic pull 

Tensile 

Tensile 

load 

load 

Stator core 

Stress concentration 


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Design Change 

Magnetic pull 

Tensile load 

Stator core 

The magnetic pull 

tries to bend the 

lamination and the rib 

welded on to it. 

Through this a tensile 

load arises in the 

lower edge of the rib. 

There is no stress 

concentration since 

the rib cross section 

is undisturbed. 


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Design Change 

Design Change was implemented 2005 

and is in operation in all Siemens Gearless Drives since then. 


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38’ Gearless Mill Drive, Chile 

Cracked Weld at rotor support 

� The 38’ SAG-Mill is in operation since 

September 2003 

� During the weekend of August 31, 2008 the SAG-Mill 

stopped several times and was restarted. 

Finally the air gap supervision tripped the motor and did not permit to 

restart it again on September 1, at 4:48 a.m. 

� Air gap and rotor were revised and there was found a crack of a weld 

of the rotor segment support (Picture next page) 

� Specialists from Siemens Germany arrived on September 3 at site and 

investigated the motor. They found another crack at the same segment 

and another segment with cracks. 

� They started the repair on September 4 and the mill restarted on 

September 8, 2008 at 9:10 a.m. 


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Chilean Plant 

Cracked Weld at rotor support 


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Chilean Plant 

Origin: Fatigue by mechanical stress 

The mechanical stress is caused by three effects 

� Constant stress by constant magnetic force, (does not cause fatigue) 

Fatigue is caused by variable stress 

� Variable stress by gravity, 

� Variable stress by changing magnetic force over the circumference, 

due to air gap deformation 


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Chilean Plant 

Variable Stress around the circumference 

Small air gap 

higher force 

Normal air gap deformation during operation 

Large air gap 

smaller force 


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Chilean Plant 

Provisional Repair of Rotor Segment 


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Chilean Plant 



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Chilean Plant, 



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Defect of rotor segments; 

Consequences for other users 

� Siemens investigated the possibility of similar damages in other 

Ring Motors and informed in September 2008 three other users to 

inspect the rotors: 

� Other Chilean Plant 

Inspection was performed during mill maintenance in February 2009: 

no findings 

� Australian plant 

Inspections were performed during plant maintenance in November 

2008 and February 2009: 

cracks were found and provisionally repaired; 

2 additional days of downtime; 

� Indonesian plant 

Inspection was performed during plant maintenance in April 2009 

cracks were found and provisionally repaired; 

12 additional hours of downtime; 


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Chilean Plant 

Final Repair of Rotor Segment 

The final repair of the rotor segments were planned from 

June 30, 2009 to July 14, 2009, 

parallel to a mill maintenance (liner change) . 

After replacing 4 segments, turning of motor for positioning was 

interrupted by earth fault. 

There were found foreign objects in the air gap, which had damaged 

stator windings and rotor coils. 

Repair of windings and coils was finished August 10, 2009 

without completion of rotor segments. 

A failure of the feeding switchgear delayed the restart of production for 

another two days. 

Caused Downtime: 43 days minus 4 days for mill maintenance 


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Performance 

Content 





Chilean Plant, Rotor failure 



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Downtime, Availability 

Major downtimes for repair: 

� Cadia, Vibrations, 

� Cadia, defect at the rotor segments, 

� Chilean Plant, defect at the rotor segments, 

� Australian plant, defect at the rotor segments 

� Indonesian plant, defect at the rotor segments 


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Cadia; Vibrations 

� Downtime for repair: 7 days minus 5 days for liner change 

Cadia; Defect of rotor segments 

� During 2003 Cracks of welds at rotor support were found and 

provisionally repaired. 

Downtime: 5 days for investigation and repair 

minus 4 days for liner change. 

� In 2005 the final repair was performed with a downtime of 15 days. 

� Downtime for repair: 15 days minus 4 days for liner change 


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Chilean plant; Defect of rotor segments 

� September 1, 2008 the air gap supervision of the 38’ Ring 

motor tripped the mill. Cracks were detected and provisionally 

repaired. September 8, 2008 the 38’ mill was restarted. 

9 days of unscheduled downtime 

� First part of final repair in 2009 including repair of occurred damages: 

Downtime: 43 days minus 4 days for mill maintenance 

� Scheduled completion of final repair in 2010: 

Downtime: 15 days minus 4 days for liner change 


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Major downtimes for repair: 

� Cadia, Vibrations: 2 days 

� Cadia, defect at the rotor segments: provisional repair: 1 day…. 

final repair: 11 days 

� Chilean plant, defect at the rotor segments: 2008: 9 days 

First part of repair in including repair of damages 2009: 39 days 

final repair, scheduled 2010: 11 days 

� Australian plant, defect at the rotor segments: 2009: 2 days 

final repair, scheduled 2010: 14 days 

� Indonesian plant, defect at rotor segments: 2009: 0.5 days 

final repair, date to be defined: 10 days 

Total sum 99.5 days 


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Performance 



105,000 

Machine days 


With major downtimes of in total 99.5 machine days 


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Thank you for your attention! 

Contact: 

Kurt Tischler 

Siemens AG 

Metals Technologies 

Mining Industry 

W-v-Siemens-Str. 50 

91052 Erlangen / Germany 

Phone: +49 (9131) 7-42420 

Mail: kurt.tischler@siemens.com 


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Gearless Mill Drives - Cbmua.org

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