The bearing clearance and the condition of the babbit-bearing surfaces and of the antifriction bearings should be checked, and the shaft diameter should be measured at the bearing surface. The condition of the oil or grease should be checked, and the lubricant should be changed as required.
The general condition of the rotor and rotor blades should be checked, and loose blades should be fixed. Couplings should be examined, and the alignment of all parts should be inspected. If any parts are out of alignment, the cause should be determined and corrective action should be taken. Any dampers should be tested for ease of operation and freedom from obstruction.
Induced-draft fans are subject to erosion and corrosive attacks from ash particles and flue gas. In addition to the inspections discussed in preceding text, inspections of the rotor blades and casings should be made for corrosion, excessive thinning, and holes in the blades and casing. The shaft should be examined for corrosion from dew-point condensation near the casing. Missing or faulty gasket seals around the shaft will allow the entry of cold air and lead to condensation and subsequent corrosion. Rotor blade surfaces should be checked for cracks with magnetic particle testing or penetrant testing focusing on stress riser locations.