This document 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 (including
synchronizing clutches). This document 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.
This document 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 7919-3 and ISO 10816-3)
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 7919-3 or ISO 7919-4 and ISO 10816-3
or ISO 10816-4)
v) the evaluation of combustion vibration but does not preclude monitoring of combustion vibration.
INTERNATIONAL STANDARD ISO 20816-2:2017(E)
© ISO 2017 – All rights reserved 1

ISO 20816-2:2017(E)