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 heavy-duty gas turbine sets used in electrical and mechanical drive applications, with fluid-film bearings, outputs greater than 3 MW and an operating speed range under load between 3 000 r/min and 30 000 r/min. This includes gas turbines coupled to other rotating machinery either directly or through a gearbox. In some cases, this part of ISO 10816 is not applicable to the evaluation of the vibration of the coupled equipment (see the list of exclusions in this clause). EXAMPLE For single-shaft combined-cycle power units in which a gas turbine is coupled to a steam turbine and/or generator, the evaluation of the gas turbine vibration is according to this part of ISO 10816, but that of the steam turbine and generator is according to ISO 10816-2 or ISO 10816-3. This part of ISO 10816 is not applicable to the following: a) aero-derivative gas turbines (including gas turbines with dynamic properties similar to those of aero-derivatives); NOTE ISO 3977-3 defines aero-derivatives as aircraft propulsion gas generators adapted to drive mechanical, electrical or marine propulsion equipment. Large differences exist between heavy-duty and aero-derivative gas turbines, for example in casing flexibility, bearing design, rotor to stator mass ratio and mounting structure. Different criteria therefore apply for these two turbine types. b) gas turbines with outputs less than or equal to 3 MW (see ISO 10816-3); c) gas turbine driven pumps (see ISO 10816-7); d) coupled steam turbines and/or generators with outputs less than or equal to 50 MW (see ISO 10816-3); e) coupled steam turbines and/or generators with outputs greater than 50 MW (see ISO 10816-2); f) synchronizing clutches which couple the gas turbine to a steam turbine or generator (see ISO 10816-2); g) coupled compressors (see ISO 10816-3); h) gearbox vibration (see this clause); i) rolling element bearing vibration. This part of ISO 10816 is applicable to other driven equipment not included in this list of exclusions. This part of ISO 10816 is applicable to machines which can be coupled to a gearbox, but does not address the evaluation of the vibration condition of those gears. Specialist techniques are required for evaluating the vibration condition of gears which are outside the scope of this part of ISO 10816. The numerical values specified are not intended to serve as the only basis for judging the severity of vibration. For gas turbine sets, 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 7919-4.