6.5.4 If specified, corrosion-resistant shaft sleeves shall be provided. Sleeves shall extend 6 in. (150 mm) into the fan housing or to the impeller hub. Shaft sleeves shall be installed with an interference fit, and the fit and assembly shall take into account differential thermal expansion at the highest operating temperature. After assembly of the shaft, mechanical run out on the shaft sleeve shall not exceed 0.002 in. (50 μm) total indicated runout (TIR) in the seal area.