The use of expanders in the preparation stage of oil extraction has centered on their ability to increase tonnage, and improve drainage for deep bed extractors. The Crown shallow bed extractor does not suffer from percolation problems but never the less, can include expanders if deemed beneficial to the overall process. Indeed we normally recommend them, especially large sunflower and cottonseed plants as a more economical and energy saving option to using pre-presses.

An expander is a continuous, controlled mechanical pressure cooking & cell rupturing device. The addition of steam "expands" the material, improving its extractability by creating an increased porosity in the pellet or "collet" form. The unit can have an integral oil expelling section to recover a quantity of oil when higher oil content seeds are processed

Expanders were first developed by Anderson International in the USA from their success with extrusion cooking devices. Today, both Solvex™ and Hivex™ series expanders are available for capacities up to 1700mtpd on soyabeans and 600mtpd on high oil content material. The latest innovation is the Dox™ design. This idea uses mechanical energy to cook and shear the seed, and the use of an adjustable jaw choke arrangement to encourage effective rupturing of the seed's cellular structure. One of the most promising applications for this technology is the high temperature, short residence time cooking as a possible replacement for traditional stack cookers, and for increasing oil expelling-efficiencies in screw presses.