Reduction of zinc consumption in hot-dip galvanizing

A hot-dip galvanizing plant asked us to collaborate to reduce their zinc consumption, which was quite high. The benchmarking established in the sector for this sector is usually very disparate due to the great diversity of different materials that are galvanized, in terms of weights, sizes, shapes and thicknesses. But, even so, it is assumed that if the plant shows a consumption above 5.0% in zinc intake, then it has options to improve.

The plant we were talking about had the following initial numbers at the time of the production audit:

  • Production: 1.140 tons/month
  • Dips per hour: 1,7
  • Efficiency: 23%
  • Productivity Kg/p/h: 54,8
  • Zinc consumption: 57,5 Kg/tons
  • Dross generation: 7,4 Kg/tons
  • Ash generation: 13,4 Kg/tons
  • Hydrochloric consumption: 23,2 Kg/tons
  • Non-conformities: 1,19% (of those 6% were external)

We carry out a complete implementation of Lean Manufacturing methodologies in the plant, as described in our Lean Galvanizing ™, but also Six Sigma oriented to two projects: reduction of consumption (zinc take was almost 7%); reduction of non-conformities, for which the plant showed a sigma level of 3.76.

Through VSM we evaluated that, in general, the plant had a Lead Time of 4.43 hours, without counting the storage time in “white”. This average time was distributed in a very irregular way by the different families of material received, from 1.9 hours for heavy material to 5.3 hours for laminates and even more than 52 hours for centrifuged. The plant worked three shifts and was unable to fully respond to market demand.

Our in-depth knowledge of the galvanizing processes and the use of Kanban-Heijunka methodologies allowed us to dramatically improve assembly, pickling and reworking times. The Lead Time became 2.72 hours: 38.5% less. Instead of 1.7 hour dives, he went on to do 3.3. Almost double.

Well-applied galvanizing best practices, together with careful statistical control of the process, achieved two beneficial effects at the same time: on the one hand, reducing non-conformities to 0.28% (equivalent to a sigma level of 4.3) ; on the other, reduce zinc take by 3.6% and dross/ash production by 26%.

With these improvements, the final numbers of the plant were as follows:

  • Production: 1,780 tons / month
  • Dives per hour: 3.3
  • Efficiency: 36%
  • Productivity Kg / p / h: 58,7
  • Zinc consumption: 55.4 Kg / tons
  • Dross generation: 4.9 Kg / tons
  • Ash generation: 10.4 Kg / tons
  • Hydrochloric consumption: 20.5 Kg / tons
  • Non-conformities: 0.28% (none external or customer)
Do we translate it into money? The improvements in consumption meant an annual saving of 250,000 dollars and the increase in productivity translated into sufficient capacity to make an additional 2 million dollars a year, or what is the same, a possibility of increasing its market share by 40% while maintaining or even lowering prices.


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