Predisposition is shown of small capacity units to low frequency vibration (LFV) provided that the unit shaft contains a flexible clutch. Mechanism is examined of units break down into low frequency vibration as a result of a connecting clutch malfunction. Some examples are presented of LFV originating at PT-60-130 turbine and K-1700 compressor unite. As it is shown by practical experience the defining factor of unit low frequency vibration break down could be flexible clutch unsatisfactory operation.