Degree Name

Doctor of Philosophy


Department of Mechanical Engineering


Crustbreak/feeding systems in prebake aluminium smelting pots are critical to efficient pot control as they contribute in a large way to the alumina balance in the pot. Inefficient feeder and pot operation may cause emission of global warming gases, severe cost penalties and may affect the health and safety of operating personnel This study investigated the causes of failure and the performance of existing designs. Most of the research was conducted at Portland Aluminium (Victoria) and contact was made with about 30 smelters world-wide.

Methods have been developed to improve shot size accuracy, reduce costs, increase crustbreak/feeder life and improved the safety of operators and tradespersons. New designs were developed and two were subsequently patented in Australia, New Zealand South Africa and the U.S.A.

Over 30,000 measurements were taken of dose mass on 7 different feeder designs. Changing the shape of the dosing unit to accommodate better alumina flow rate reduced the standard deviation of the shot size to 0.6% of shot mass for one of the patented designs and 1.9% for the most commonly used pot feeder (compared to an original 7- 14%). These figures compare with 2.5% for the Aluminium Pechiney independent design.

In the investigation into the mechanism of plunger wear and optimising materials, over 10,000 measurements of plunger diameter were taken during feeder maintenance and over 2,500 were taken in 3 monthly measurements in operating pots. Some 19 materials were tested. Plunger life at Portland increased from 1 year to 8 years (for plant scale operation) and trials in operating pots achieved life up to 15 years for one design.

Feeder life at Portland improved by over 80% and repair costs reduced by $1.4m per annum. Feeder life improved from 9 months to 55 months. Many recommendations have been shared at many smelters which has led to significant benefits in improving the existing crustbreaker/feeder units used across the world.