This part of ISO 10816 establishes provisions for evaluating the severity of in-situ, broad-band vibration measured radial (i.e. transverse) to the shaft axis on all main bearing housings or pedestals and in the axial direction on thrust bearings. These are in terms of:- vibration under normal steady-state operating conditions; - vibration during other (non-steady-state) conditions when transient changes are taking place, including run up or run down, initial loading and load changes; - changes in vibration which can occur during normal steady-state operation. This part of ISO 10816 is applicable to land-based steam turbines and generators with power outputs greater than 50 MW and a normal operating speed of 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min. It is also applicable to 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 10816 apply only to the steam turbine and the generator (including synchronizing clutches). ISO 7919-4 and ISO 10816-4 are applicable to the evaluation of the gas turbine vibration.The evaluation criteria in this part of ISO 10816 are not applicable to the electromagnetic excited vibration with twice line frequency at the generator stator core and housing. The numerical values specified are not intended to serve as the only basis for judging the severity of vibration. For large steam turbines and generators, it is also common to judge the vibration based on measurements taken on the rotating shafts. For such vibration measurement requirements, see ISO 7919-1 and ISO 7919-2.