Qantas Airways Limited operates domestically within Australia and flies internationally to Asia, Europe and the USA. Its routine overseas flights provide some of the longest sectors flown by any airline. Qantas currently has thirty one 747 ëjumboí and twenty 767 wide bodied aircraft in its fleet.
Qantas aircraft are painted with a coating which must provide effective corrosion protection for up to a decade. In addition, the coating must withstand a wide range of climatic conditions, including temperatures from minus 60 degrees to plus 45 degrees Celsius, snow storms and tropical downpours.
Prior to repainting the aircraft the old paint must be completely removed. Paint stripping is undertaken at the jet maintenance base located at Mascot Airport. Traditionally this was done using a methylene chloride and phenol based stripping solution which was washed off after removing the paint. Between 1,000 to 1,200 litres of solution was used per aircraft.
The phenol contaminated paint waste was difficult to treat and resulted in high trade waste costs when disposed to the sewer.
The stripping was undertaken in a hanger and due to the hazardous nature of the stripping solution no other activities could be undertaken while stripping was taking place.
Cleaner Production Initiative
Qantas investigated a number of alternative paint stripping approaches.
One significant constraint upon the airline in considering various approaches was that it was tied to traditional techniques so as not to void the aircraft warranty.
One of the possibilities was a benzyl alcohol based product. This had been previously tried by a number of other airlines, but had achieved mixed results in terms of paint removal. Qantas persisted with the benzyl alcohol treatment, tightening the application conditions and insisting upon product guarantees from the supplier, and have subsequently achieved satisfactory results.
There were two disadvantages with the new system:
- It initially took eight to ten hours to lift the paint from the fuselage compared with one to two hours for the methylene chloride stripper. Subsequent optimisation of the process has reduced this time to approximately four hours, and
- the price was approximately fifty per cent more than the methylene chloride and phenol product.
Qantas rearranged its maintenance program so that the extended time required for paint stripping was linked with a late night shift.
The dry paint residue is manually dislodged and collected on kraft paper that has been laid out beneath the aircraft. The paint residue, comprising approximately 200 kg of material per aircraft, is suitable for disposal at an approved landfill site.
Qantas is currently undertaking further development on this process to strip the areas where more chemically resistant paints are used. A number of overseas airlines have now expressed interest in using this procedure.
Advantages of the Process
The disposal costs for methylene chloride and phenol paint stripper solution was approximately $40,000 per aircraft. Using the bio-degradable benzyl alcohol has eliminated this waste disposal cost. Although the cost of the benzyl alcohol is $4,000 more expensive (per plane), productivity gains from now being able to use the hanger during stripping far out weigh the additional cost. With a fleet of some 97 aircraft, this cleaner production initiative offers significant cost savings for Qantas.
The airline was able to use the existing facilities and methods to implement the new benzyl alcohol paint stripping procedure. Maintenance personnel were trained in its application and it was possible for the new process to be introduced as a straight change from the old.