This part of ISO 10816 gives guidelines for applying bearing housing vibration evaluation criteria measured under normal operating conditions at the bearings, bearing pedestals or bearing housings of the main machine sets in hydraulic power generating and pumping plants. These guidelines are presented in terms of both steady-state running vibration and any amplitude changes which may occur in these steady values. The numerical values specified are not intended to serve as the only basis for vibration evaluation, since, in general, the vibratory condition of a machine is assessed by consideration of both the bearing housing vibration and the associated shaft vibration (see introduction of ISO 10816-1 and ISO 7919-1). This part of ISO 10816 is applicable to machine sets in hydraulic power generating and pumping plants where the hydraulic machines have speeds from 60 r/min to 1800 r/min, shell or shoe type sleeve bearings and a main engine power of 1 MW and more. The position of the shaft line may be vertical, horizontal or at an arbitrary angle between these two directions. Machine sets covered by this part of ISO 10816 may be combined from — hydraulic turbines and generators, — pumps and electrical machines operating as motors, or — pump-turbines and motor-generators. Auxiliary equipment (e.g. starting turbines or exciters lying in the shaft line) is included. Evaluation criteria are at present only given for the main bearings of the machine set. This part of ISO 10816 is applicable also to single turbines or pumps connected to generators or electrical motors over gears or/and radially flexible couplings. However, electrical machines of this type should in principal be evaluated according to the criteria specified in ISO 10816-3. This part of ISO 10816 is not applicable to the following: — pumps in thermal power plants or industrial installations (for these machines, see ISO 10816-3); — hydraulic machines or machine sets having rolling element bearings. Consistent with clause 1 of ISO 10816-1:1995, bearing housing vibration of machine sets in hydraulic power generating and pumping plants may be determined with regard to following tasks: — task A: monitoring changes in vibrational behaviour; — task B: prevention of excessive kinetic load. The criteria are applicable mainly for the vibration produced by the machine set itself. Special considerations should be made when necessary for vibration transmitted to the machine set from external sources.