ISO 20816-2:2017 is applicable to land-based gas turbines, steam turbines and generators (whether coupled with gas and/or steam turbines) with power outputs greater than 40 MW, fluid-film bearings and rated speeds of 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min. The criteria provided in this document can be applied to the vibration of the gas turbine, steam turbine and generator and other shaftline components (such as synchronizing clutches, exciters or flywheel masses). ISO 20816-2:2017 establishes provisions for evaluating the severity of the following in-situ, broad-band vibration:

a) structural vibration at all main bearing housings or pedestals measured radial (i.e. transverse) to the shaft axis;

b) structural vibration at thrust bearing housings measured in the axial direction;

c) vibration of rotating shafts radial (i.e. transverse) to the shaft axis at, or close to, the main bearings.

These are in terms of the following:

- 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.

ISO 20816-2:2017 is not applicable to the following:

i) electromagnetic excited vibration with twice line frequency at the generator stator windings, core and housing;

ii) 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.

iii) steam turbines and/or generators with outputs less than or equal to 40 MW or with rated speeds other than 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min (although generators seldom fall into this latter category) (see ISO 20816-3);

iv) gas turbines with outputs less than or equal to 40 MW or with rated speeds other than 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min (see ISO 20816-3 or ISO 20816-4);

v) the evaluation of combustion vibration but does not preclude monitoring of combustion vibration.