Energy savings for PET container production
Retrofittable action package

Where can costs be cut in the stretch blow-moulding process? When the production costs for PET containers are examined, the biggest factor involved is the material costs for PET, which account for over 70 per cent of the total. The rest are divided more or less equally between preform manufacture and the stretch blow-moulding process. Of the approximately 13 per cent of total costs accounted for by stretch blow-moulding, around 23 per cent in their turn are attributable to the operating costs involved.

Saving energy on heating
In the stretch blow-moulding process, energy costs for heating can be reduced firstly by replacing the lamps at regular intervals, and secondly by checking the distance between the lamps and the preforms. Studies have shown that old lamps (after approximately 11,000 operating hours) require up to 30 per cent more energy than new ones. Regular checks and stringent lamp replacement are accordingly advisable. The second cost-cutting factor is the distance between the lamps and the preforms: in the lamp case newly developed by Krones, the lamps are positioned closer to the preforms. This new oven standard, which is also retrofittable, produces an approximately 10-per-cent reduction in energy consumption during the heating function.

Minimising consumption costs in the blow-moulding process
During blow-moulding, a reduction in the volume of dead space can likewise minimise the consumption costs involved. Downsizing the volume of the valve block and the blow nozzle from 500 ml to 250 ml does not entail any disadvantages in terms of process engineering, since the cross-sectional areas for the flow remain the same. This downsizing is a standard feature for new Contiform machines and available as a retrofit kit for stretch blow-moulders already installed. By downsizing the volume that has to be filled with pressurised gas, savings of more than 7 per cent (in the case of 500 ml up to 25 per cent) can be achieved in air consumption costs, depending on the size of the container involved.

Air recycling
One significant cost-cutting factor for blow-moulding is air recycling using the Air Wizard, which acts in three or four stages. If the final blow-moulding air is recycled for pre-blowing, the energy costs are already being cut by around 9 per cent. If this recycling is used not only for the pre-blowing function, but also for stretching, energy savings are already running at 22 per cent. If the recycled air is fed back into the operating air network, energy savings of 30 per cent can be achieved, and if the recycled air is fed back directly into the compressor, energy costs can even be cut by 40 per cent a year. Clients operating Contiform machines from the S series can retrofit their stretch blow-moulders with all these variants, thus helping to cut their operating costs significantly.