Statistical Control of the Quality of Decanters Used for the Continuous Virgin Olive Oil Extraction

It was set up a study of a diagnostic program by means of specific Quality Control Charts. The quality control was carried out on 14 AMENDUNI REX-250 two-phase decanters, according to ISO 20816-1: 2016 standards. The machines were studied at rotational speeds 3,000 rpm, 2,900 rpm, and 2,800 rpm. The tested decanters provided the best performance in terms of process controllership at 3,000 rpm. The machines that reported significant anomalies at the maximum number of revolutions were those balanced on lower rotation speeds which is usual in the extraction of virgin oil. It was possible to identify the most stressed sections of the machines at all speeds; these were the closest to the engine and on the left side of the basin (the side where the machine is set in rotation by the branch of the belt transmission). The possible causes of the anomalies are: unbalanced bowl, incorrect assembly of the bearings and, more rarely, defects and damages in the raceways, balls or rollers. The process carried out by the manufacturing company was adequately monitored, in accordance with current technical standards. On the top of the regulations, the statistical quality control of the balancing process shows to be free to the non-natural variability according to one of the criteria and seems that no further improvement to the process are needed. However, the control chart tool provides an efficient breakdown of the current state of quality of the process. Eventually, other criteria may be explored to fully determine the degree of control on the explored process.