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Repair of Cement Mill Shell Crack

 CEMENT MILL FOR GRINDING

  • Ball mill: It is a horizontal cylinder partly filled with steel balls (or occasionally other shapes) that rotates on its axis, imparting a tumbling and cascading action to the balls.
  • Material fed through the mill is crushed by impact and ground by attrition between the balls. The grinding media are usually made of high-chromium steel.

X’tra life welding treatment : cement mill shell crack

Repair of Cement mill shell crack of 90 tonnes per hour capacity.

WRTPL SOLUTIONS : 

Wear Factors : Impact Load

  • Analysing the cause of crack & its nature and depending on the working parameters , WRTPL  suggested welding alloy XL- LH and XL- HTS NM for repair of the complete crack.

          Product   :   XL- LH
          Size   :  3.15mm
          Product   :  XL-HTS NM
          Size   :  2.5mm and 3.15mm

Product name

Specifications

XL- LH

•Special coated electrode high grade and crack resistant welds on hydrogen controlled steels.

•Tensile strength – 650 N/mm²

•Elongation – 30% (approx)

XL- HTS NM

•It is a specially developed electrode for repair welding of  critical material where  normal joining electrode does not meet required weld specifications.

•Extra care is required for welding/repairs of critical steels can be avoided using this alloy, especially get rid of  problems like cold cracking using the same.

•Low heat input electrode for welding of critical maintenance because of its mechanical characteristics.

•Tensile strength – 670 N/mm²

•Elongation – Min.40%

Welding procedure :

  • Weld process : MMAW
  • Welding machine : 2 nos. rectifier (600 amps)
  • Electrode diameter : 2.5 mm and 3.15 mm
  • Polarity : DC +ve
  • Current : 120-135 amperes (minimum current to be used)
  • Welding technique : Stringer bead
  • Before welding : Surface preparation to be done. Tools and tackles to be ready (wire brush, chipping hammer, etc.)

Stage-1 

  • Arrangement of scaffolding with customer help due to the height of the crack in ball mill shell is approx 15 feet.
  • WRTPL  technicians and welders have taken all safety measures as per the company guide lines.
  • First of all removing all strengthening bars throughout the crack area by grinding and carbon arc gauging for faster option.
  • Cleaned the crack area with wire brush.
  • Gouging of cracks with carbon arc gouging electrodes from outer side up to 25 mm.
  • Grinding the crack area in U- groove by wheel grinder for removing carbon and defects.
  • After analysing full crack length a hole was drilled 20 mm dia. after 50 mm of crack extremities on both end by drillings machine to avoid the propagation of crack.
  • DP test of crack / MPI / UT.

Welding process : 

  • Preheated the crack portion up to 150°C @ 50°C / hour.
  • Maintained the inter pass temp. during the welding process 250-275°c
  • Slag removal & peening done.
  • Place dia. 16 mm SS  tube in crack portion on length of crack and join it with XL-HTS NM electrode.
  • XL-LH used as base layer for fatigued portion, and filling by XL-HTS-(NM) (Nickel Based) on U- Groove.
  • After this repair is done, gouge about 100 mm length up to about 6mm depth at every 150 mm and place and weld strengthening bars across the joint. the bars dia. 12-14 mm will be in EN-8 and the bar ends not to be strictly welded.
  • Grinding and finishing and checking of DP/MPI.

WRTPL SCOPE :

  • SS tubes/strengthening rods
  • Preheating/SR by induction heating
  • Welding by our experts
  • WRTPL has successfully completed the crack repair job within 72 hours of time.

Key benefits due to successful repair of cement mill shell crack : 

  • Above case study addresses the concern of top management about reclamation of key spares rather then buying new. This approach is economical and technically superior for the society.
  • The solution in terms of repair and reclamation aware society to adapt better metallurgical upgrades and innovative processes to improve the availability of the plant and machinery.
  • Overall, this thereby reduces the downtime losses and operational costs resulting into absolute improvement of the bottom line for the organization.