The document provides specific guidance for assessing the severity of radial vibration measured on the shafts of steam turbines and generators in situ. The criteria provided in this document apply to steam turbines and generators exceeding 50 MW, and with a nominal operating speed of 1500 r/min, 1800 r/min, 3000 r/min and 3600 r/min. It also includes steam turbines and/or generators which are directly coupled to a gas turbine (such as for combined-cycle applications). In such cases the criteria of this part of ISO 7919 apply only to the steam turbine and the generator (including synchronizing clutches). Two criteria are provided for assessing the machine vibration when operating under steady state conditions. One criterion considers the magnitude of the observed vibration; the second considers changes in the magnitude. In addition, different criteria are provided for transient operating conditions, such as run-up and coast-down. The evaluation procedures presented in this part of ISO 7919 are based on broad-band measurements.