$($A$)-$ Vibration Case StudyExcessive vibration in a fanCentrifugal fan on foundation used to forceheated air over drying maltSpecification: $2\mathrm{.}5$ m dia impeller. Spherical roller bearings. Multiple v$-$belt drive.Operation problems: Pulsations, on closure of inlet vanes $($flowcontrol device$).$ Excessive vibration levels in spite of carefulimpeller balancing. Prominent second and third harmonics in thefrequency spectrum. When run down, irregular knocking noisesproduced.Also damage to machine identified on inspection: Failure of two $24$mm bolts holding steelpedestal to concrete foundation block. Partial disintegration of grouting betweenpedestal & foundation. Some damage to shaft surfaces wherebearings attached.