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Presentation done at the TMS conference, 2007 held in Florida, USA.

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  • 1. BALCO FUSE TECHNOLOGY
    • J.Ramaswamy
    • Bharat Aluminium Company Limited
    • (A member ofVEDANTAResources plc.)
    • India
    2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA

2. Contents

  • Introduction
  • Present Technology
  • Innovation
  • Principle
  • Design
  • Observation
  • Further Modification
  • Result

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 3. Introduction<

  • VISION
  • To achieve global standards of excellence in productivity and customer satisfaction
  • TECHNOLOGY
  • GP 320 Potline - GAMI Technology,China
  • 288 pots Single pot line ( Two rooms )
  • 2,45,000tons Al / annum
  • 540 MW Captive Power Plant

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 4. Present Technology<

  • No provision for online power on of pots.
  • As per the GAMI design, power outage was required every time a pot is put on preheat.
  • The shorted riser joint bolts are loosened and a gap is made at the joint to insert the insulation plates at 0 kA to put the pot on power.(fig.)
  • This procedure of putting pots on power involves 6-10 minutes at 0 kA along with 30-35 minutes of power reduction (320 kA 0 kA and 0 kA to 320kA)

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 5. Innovation>

  • Two fuses per riser were designed to by pass the line current, till the pot was cut into the circuit. After a calculated safe period of time, the fuses melt resulting in the pot coming into potline circuit.
  • Fuse assembly - Two fuse blocks, a Fuse and three types of fuse clamps(fig.)
  • Fuse block is designed to maintain proper contact with the riser and as a platform to clamp the fuse.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 6. Innovation (contd..)<

  • Clamp 1 is used to clamp the fuse block with the riser.
  • Clamp 2 is used to clamp the fuse block with the shorted joint bus bar(fig.)
  • Clamp 3 is used to clamp the fuse with the fuse blocks.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 7. Principle>

  • Prior to the power on of the pot, fuse assembly is fitted on lower part of all riser with clamps.
  • When the shorted riser joint is opened for the insertion of insulation plates, the circuit is temporarily completed through the fuses.
  • These fuses by pass the line current for a calculated period of 10 minutes, till the pot is cut into the circuit.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 8. Principle (contd..)<

  • During the increase of current to 320 kA in steps, the fuses melt and the pot is put on power.
  • With the fuse technology, power on takes 20-25 minutes with around 6-10 minutes at 240 kA.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 9. Design>

  • The dimensions for the fuse were calculated
  • Based on Resistivity.
  • Based on the thermal stress due to short circuit current .
  • Electrical fusing time principle.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 10. Design(contd..)>

  • Based on Resistivity
  • R= V / IandR = l / A
  • Where R = resistance in
  • V = Voltage drop in Volts
  • I = Current in Amps
  • = resistivity of Al at 200 c
  • l = Current in Amps

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 11. Design (contd..)>

  • Based on the thermal stress due to short circuit current .
  • I k* 1000 * t
  • A =
  • [4.184 {(c* d )/ ( r* )} ln {1 + (V max V 1 )}]
  • Where,A= cross sectional area of the fuse
  • I k= current in kA t= time in seconds
  • c= specific heat of Aluminium
  • d= density of Aluminium
  • r= resistivity of Aluminium at ambient temperature
  • = 0.004 V max= Maximum temperature
  • V 1= initial temperature

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 12. Design (contd..)<

  • Electrical fusing time principle.
  • I * 33 * S
  • A m=
  • log 10[{(T m T a ) / (234 + T a )} + 1]
  • where I= current in amps
  • A m= conductor area in circular mills
  • 1 circular mill = 0.7854 mil 2
  • 1 mil= 1/1000 inch
  • S= time in seconds
  • T m= melting point of aluminium
  • T a= ambient temperature

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 13. Observation<

  • With the fuse technology, power on takes 20-25 minutes with around 6-10 minutes at 240 kA as compared with 30-35 minutes with around 6-10 minutes at 0 kA without fuse(fig.)
  • The results have shown that 100% of the fuses have melted(fig.)

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 14. Further Modification<

  • Although pots could be powered on at full line current of 320 kA but to be on safe side, the line current is reduced to 240 kA.
  • The numbers of preheat shunts were increased to bypass a higher percentage of current, as the line current is brought up to 320 kA.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 15. Result>

  • The saving is $ 1.4 million for starting up of the pot line of 288 pots.
  • Disturbances to the operating pots due to frequent power outages are eliminated.
  • No negative impact on the power plant operation as well as on its equipment.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 16. Result (contd..)>

  • Comparatively negligible production losses due to only nominal decrease in line amperage during power on of pots.
  • GP 320 technology is enhanced by this innovation and becomes more competitive in the world market.

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 17. Thank You 2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 18. 2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA Shorted Joint< 19. 2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA Fuse Assembly< 20. 2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA Fuse Assembly fitted on riser< 21. Current vs. Time Graph< 2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 22. Status of Fuse< 2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 23. Savings2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA 24. Line current increase in steps

  • 0-80-160-240-280-320

2007 Annual Meeting; February 25-March 1, 2007 Orlando, FL, USA