In heavy-duty decanter centrifuges used to produce polyvinyl chloride, the moving assembly and other parts in contact with the process fluid are made entirely of Ferralium® 255 super duplex stainless steel (UNS S32550, Alloy 255, DIN 1.4507, ASTM F61). It significantly reduces the risk of stress corrosion cracking that affected the austenitic stainless steels used previously.
Thomas Broadbent & Sons, Limited, of Huddersfield, manufacture heavy-duty decanter centrifuges used extensively in the chemical, petrochemical, mining and mineral-treatment and other process industries worldwide. Applications include separating crystalline and granular solids from liquids, drying fine solids, and classifying solids by particle size.
Why Ferralium® 255
In PVC production, the retention of some chlorides under slightly acid conditions within the slurry, together with the elevated temperature, can cause stress corrosion cracking and blistering of the standard 18/10 and 18/10/3Mo austenitic stainless steels previously used. Ferralium® 255 has proved its superiority over austenitic stainless steels under these arduous conditions, greatly increasing service life.
The conveyor component
The conveyor is an Archimedian spiral approximately 4'0" long, tapering from 2'0" to 2'6" in overall blade diameter, formed and welded from ¼" Ferralium® 255 plate. The spiral is carried on a central tube of 1'5" diameter, rolled and welded in ½" plate. This component, fabricated by F. Pedley & Sons Limited of Chadderton, Lancs, clearly demonstrates the weldability of Ferralium® 255.
