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September 1998
Summary
The implementation of a waste minimisation strategy has reduced
the company's waste generation. Employee waste minimisation training
has led to an improvement in process integrity and product quality.
The greatest gains have been made by improving work practices
at the flux stage of the process. Cost savings from all work practice
changes are approx $100,000 per annum.
Business Profile
Korvest Galvanisers is a publicly listed company and the
largest hot dip galvanisers in South Australia. The company has
been operating at its current site for the last 14 years and has
a workforce of 55.
Financial assistance provided
ICI Watercare Consultants carried out the consultancy study
with a grant of $15,000 provided by the EPA's Cleaner Industries
Demonstration Scheme.
Measures implemented
Source reduction of waste.
Cleaner production motivators
Improve product quality, reduce operating costs.
Traditional approach
The company uses a galvanising method that has remained largely
unchanged for 150 years. A reduced level of ammonia in the flux
decreases flux performance and the efficiency of the galvanising
process. The flux was 'topped up' at the end of each week with
zinc ammonium chloride in an attempt to maintain flux quality.
Reworks were running at 3.5%, costing $100,000 per annum in lost
production and rework costs.
Waste management
| Waste stream description |
- Spent acid, caustic rinse water, acid rinse water.
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| Process generating waste |
- The steelwork is dipped into a series of baths containing
pretreatment chemicals followed by air-drying and a dip
in molten zinc. The hot galvanised work is quenched in
a post treatment chemical with manual 'fettling' to remove
unsightly barbs and run off from the completed work.
- The main source of waste is from the removal of paint
and surface oxidation from the fabricated steel.
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| Waste stream composition |
- Waste acid, waste caustic and sludge.
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| Disposal methods |
- Approx 10-12 tonnes of spent acid per week was taken
by a licensed liquid wastes contractor.
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| Cost of disposal |
- 1995 waste removal costs were in excess of $150,000.
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Cleaner production initiatives
Benefits recommended and implemented
Work practices
The changes made to work practices were vital to the success of
the project which involved training the workforce in waste minimisation.
Changes included:
Flux
The flux was analysed during periods of poor galvanising and it
was found that the ammonia level was far from optimum. Traditionally
zinc ammonium chloride had been added to the flux at the end of
each working week to maintain flux quality, so for the last day
of the working week, the flux was in a very poor state. The practice
of continuous air sparging of the flux bath to reduce iron content
caused the ammonia to dissipate to the atmosphere.
New approach:
- The flux is measured for ammonia, zinc and chloride content
once per week.
- Zinc ammonium chloride is added daily in a smaller amount.
- Ammonia solution is added daily.
- Steelwork is dipped in the flux bath for a longer time to
allow it to equilibrate with the bath temperature.
Jigs
Employees were trained to ensure that as little as possible of
the jig, which holds the items to be galvanised, is coated with
zinc to ensure that zinc does not contaminate other stages of
the process. The jig design was also modified to ensure that as
little as possible of its surface is dipped into the process baths.
Acid rinse
Larger items had not been rinsed after the acid dip stage because
the rinse tank was too small. Process modifications ensured the
acid rinse tank could accommodate the larger items.
Benefits
| Environmental |
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| Waste reduction |
- Less zinc usage. The amount of dross waste produced
has been reduced by 4.5% of the weight of zinc used, and
has improved coating quality.
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| Economic |
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| Investment |
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| Productivity |
- The gains made in waste minimisation enabled the company
to be more competitive in the marketplace.
- Lower rework rates, better product quality.
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| Savings, outcomes |
- Improved quality of flux increased efficiency of galvanising
process, improved quality of product and reduced rework
rate from 3.5% to 1%, saving around $44,000 per annum.
- Total cost savings from all work practice changes:
approx $100,000 per annum.
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This page was last modified 31-07-2007
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