Dave Smith, of Columbus Stainless, Kyle Atcheson, John Cluett, formerly of SABMiller, and John Tarboton, Sassda executive director, inspect the vessel before the move to the University of the Free State
In 2000, a collaboration between Rand Afrikaans University (RAU), the Southern Africa Stainless Steel Development Association (Sassda), Columbus Stainless and South African Breweries (SAB), now ABInBev, was entered into to research the cleanability of stainless steel surfaces.
This research project was part of John D Cluett’s M Phil Dissertation “Cleanability of Certain Stainless Steel Surface Finishes in the Brewing Process” at RAU.
This project aimed to address the effect of stainless steel surface finishes on the cleanability and residual biofilms after clean in place (CIP) procedures were initiated.
This was supported by real live tests on a vessel that was large enough to carry out the experiments over a number of cycles.
Research involved the manufacture of a vessel at the SAB World of Learning. A 500 litre fermentation vessel was manufactured from type 304L stainless steel. The vessel body consisted of four quarters having different internal surface finishes. These were the standard 2B, 120 grit and 240 grit polished finishes and an electro polished finish. The base or cone was electro polished.
The vessel was manufactured by Falcon Engineering.
The cleanliness was evaluated after brewing using Adenosine Triphosphate (ATP) Bioluminescence. This is a sensitive method of evaluating the presence of bacteria. The surfaces were evaluated using 2D surface profiles measured using a Taylor-Hobson Surtronic 3 profile measurer and surface replication techniques using RepliSet, a silicon based rubber compound manufactured by Struers. The surface replicas also revealed biofilms still present after cleaning.
This technique is a first for the brewing industry. This initial work resulted in a better understanding of the effectiveness of cleaning regimes from the top to bottom of brewing vessels and to the development of standards for cleaning.
The vessel has now been in operation for more than 15 years. The vessel is being relocated to the University of the Free State and, prior to its dismantling, the surfaces were re-evaluated and compared with the measurements taken at the start of the project in 2001. This evaluation was
carried out by the Columbus metallurgical laboratory in conjunction with John Cluett, formerly of SABMiller, and John Tarboton of Sassda.
The results give important insight into the performance of different surface finishes, the deterioration of the surfaces after 15 years of brewing and important pointers as to the most cost-efficient surface finishes for brewing vessels.
The measurements taken showed no deterioration of the surfaces after 15 years in service. The polishing lines and original mill finish were as if they were produced yesterday. If one needs proof of the resilience and hygiene of stainless steel, this is it.
In a separate research done at SAB Prospecton brewery in 2000, as part of the RAU research, Columbus and Sassda carried out an in depth investigation of brewing hot and cold stainless steel equipment, vessels and piping that had been operating in a fully functional environment for a period of about 15 years. The results were very unexpected, showing heavy soil build up, insufficient CIP process, and some deterioration of the stainless steel surfaces.