Centering— Determine the centering of the stirring element shaft within the vessel for each position. Centering can be evaluated for the stirring element placed within the vessel as it would be during the test. Measure the centering with respect to the cylindrical vessel not more than 2 cm below the vessel flange. Use the centering gauge to evaluate the alignment of the stirring element and the vessel. The difference between the largest and smallest observed readings should not be greater than 2.0 mm for 360° rotation.