ISO 20816-9:2020

INTERNATIONAL ISO
STANDARD 20816-9
First edition
2020-06
Mechanical vibration — Measurement
and evaluation of machine
vibration —
Part 9:
Gear units
Vibrations mécaniques — Mesurage et évaluation des vibrations de
machines —
Partie 9: Engrenages
Reference number
ISO 20816-9:2020(E)
©
ISO 2020

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ISO 20816-9:2020(E)

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© ISO 2020
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ISO 20816-9:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General . 2
4.1 System considered . 2
4.2 Effects of the system . 2
4.3 Housing or shaft measurements . 2
5 Instrumentation . 3
5.1 Type . 3
5.1.1 General instrumentation requirements . 3
5.1.2 Shaft measurement instrumentation . 3
5.1.3 Housing measurement instrumentation . 3
5.2 Measurement frequency range . 4
5.3 Permissible errors . 4
5.4 Calibration . 4
6 Vibration measurements . 4
6.1 Shaft measurements . 4
6.2 Housing measurements . 5
6.3 Units of measurement . . 5
7 Test conditions . 5
7.1 General . 5
7.2 Arrangement of the test system . 5
7.2.1 Manufacturer's shop test . 5
7.2.2 On-site acceptance tests . 6
7.2.3 In-service monitoring . 6
7.3 Test conditions . 6
8 Evaluation criteria . 6
8.1 General . 6
8.2 Evaluation zones . 6
8.3 Acceptance criteria . 7
8.4 Vibration evaluation zone boundaries . 7
8.5 Classifications . 9
9 Test report . 9
9.1 General . 9
9.2 Manufacturer . 9
9.3 Operating data . 9
9.4 Description of the arrangement .10
9.5 Measuring equipment .10
9.6 Test measurements and results .10
9.7 Acceptance test approval .10
Annex A (informative) Rating curves for vibration displacement and velocity measurements .11
Annex B (informative) Effects of the system .15
Annex C (informative) Vibration instruments and characteristics considerations .17
Bibliography .19
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ISO 20816-9:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www. iso. org/d irectives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www. iso. org/p atents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www. iso. org/
iso/f oreword. html.
This document was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and
condition monitoring, Subcommittee SC 2, Measurement and evaluation of mechanical vibration and shock
as applied to machines, vehicles and structures.
This first edition of ISO 20816-9 is a technical revision of ISO 8579-2:1993, which was withrdrawn
in 2016.
The main changes compared to ISO 8579-2:1993 are as follows:
— It has been re-formatted to match other parts of the ISO 20816 series and includes zones A to D.
— It has two new tables for values of vibration and displacement at zone boundaries.
— A table with values for vibration acceleration rating at zone boundaries has also been included.
— The classifications table has been revised, referring to these new rating tables.
— The displacement and velocity rating graphs have been moved into an informative annex.
A list of all parts in the ISO 20816 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www. iso. org/members . html.
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ISO 20816-9:2020(E)

Introduction
ISO 20816-1 is the part of the ISO 20816 series that gives the general requirements for evaluating the
vibration of various machine types when the vibration measurements are made on both non-rotating
parts and rotating shafts.
ISO 20816-9 (this document) provides specific provisions for assessing the vibration of individually
housed, enclosed, speed increasing or speed reducing gear units. It can be used for acceptance testing,
and, by agreement between manufacturer and customer and/or operator, for guidance for routine
operational measurements.
Guidance is provided for assessing the vibration of gear units when operating under steady-state
conditions and considering the magnitude of the observed vibration. However, no criteria are provided
for transient operating conditions.
The evaluation procedures presented in this document are based on broad-band measurements.
However, because of advances in technology, the use of narrow-band measurements or spectral analysis
has become increasingly widespread, particularly for the purposes of vibration evaluation, condition
monitoring and diagnostics. The specification of criteria for such measurements is beyond the scope of
this document. They are provided in greater detail in the relevant parts of the ISO 13373 series which
establish requirements for the vibration condition monitoring of machines.
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INTERNATIONAL STANDARD ISO 20816-9:2020(E)
Mechanical vibration — Measurement and evaluation of
machine vibration —
Part 9:
Gear units
1 Scope
This document specifies requirements for determining and classifying mechanical vibration of
individually housed, enclosed, speed increasing or speed reducing gear units. It specifies methods for
measuring housing and shaft vibrations, and the types of instrumentation, measurement methods and
testing procedures for determining vibration magnitudes. Vibration grades for acceptance are included.
Torsional vibration measurements are outside the scope of this document.
It applies to a gear unit operating within its design speed, load, temperature and lubrication range for
acceptance testing at the manufacturer's facility. By agreement between manufacturer and customer
and/or operator, it can be used for guidelines for on-site acceptance testing and for routine operational
measurements.
This document applies to gear units of nominal power rating from 10 kW to 100 MW and nominal
rotational speeds between 30 r/min and 12 000 r/min (0,5 Hz to 200 Hz).
This document does not apply to special or auxiliary drive trains, such as integrated gear-driven
compressors, pumps, turbines, etc., or gear type clutches used on combined-cycle turbo generators and
power take-off gears.
The evaluation criteria provided in this document can be applied to the vibration of the main input and
output bearings of the gearbox and to the vibration of internal shaft bearings. They can have limited
application to the evaluation of the condition of those gears. Specialist techniques for evaluating the
condition of gears are outside the scope of this document.
This document establishes provisions under normal steady-state operating conditions for evaluating
the severity of the following in-situ broad-band vibration:
a) structural vibration at all main bearing housings or pedestals measured radially (i.e. transverse) to
the shaft axis;
b) structural vibration at thrust bearing housings measured in the axial direction;
c) vibration of rotating shafts radially (i.e. transverse) to the shaft axis at, or close to, the main
bearings;
d) structural vibration on the gear casing.
NOTE Vibration occurring during non-steady-state conditions (when transient changes are taking place),
including run up or run down, initial loading and load changes are outside the scope of this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
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ISO 20816-9:2020(E)

ISO 2041, Mechanical vibration, shock and condition monitoring — Vocabulary
ISO 2954, Mechanical vibration of rotating and reciprocating machinery — Requirements for instruments
for measuring vibration severity
ISO 10817-1, Rotating shaft vibration measuring systems — Part 1: Relative and absolute sensing of radial
vibration
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2041 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
gear unit
mechanical input/output device with a series of at least two meshing gears
4 General
4.1 System considered
For manufacturer's factory testing, the gear unit shall be measured and tested in such a manner as to
minimize, as far as possible, effects of the system (see Annex B). For in-field service testing, the driver
and driven machine components, mounting and other factors can influence the vibration of the gear
unit. Other International Standards and vibration evaluation can be required for measuring the driver
or driven machine when operating in-field service.
4.2 Effects of the system
Vibration magnitudes of the gear unit in field service can be adversely affected by factors beyond the
control of the gear unit manufacturer, as listed in Annex B. It is preferable to estimate the vibration of
the whole system and to check the system effects at the initial design stage of a transmission system.
The responsibility for checking should be clearly defined during this stage and all interested parties
made aware of the decision.
4.3 Housing or shaft measurements
The vibrations of a gear unit can be measured in two ways, i.e. on the housing (casing) or relative to the
shafts. Housing vibration measurements are preferred for gear units operating with rolling element
bearings when the clearance in such bearings is small and little relative movement normally occurs
between the shaft and housing.
Both shaft and housing vibration measurements are usually made on gear units operating with plain
journal bearings (fluid-film bearings). Shaft vibration measurements can provide detailed information
which is sometimes not evident from housing measurements, but only over a limited frequency range
(typically up to 500 Hz).
Care shall be taken when choosing the measurement instrument to be used for a given gear unit and
operating conditions, as each instrument has its own characteristics (see Annex C). Where possible, it
is useful to combine both shaft and housing vibration measurements to obtain the absolute motion of a
gear or a shaft.
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ISO 20816-9:2020(E)

When operating conditions during acceptance testing deviate considerably from field service, the
differences shall be taken into account in the assessment of vibration data.
5 Instrumentation
5.1 Type
5.1.1 General instrumentation requirements
Vibration shall be measured using instrumentation capable of measuring broad-band acceleration,
velocity and/or displacement, as appropriate, over frequency ranges specified below.
Care should be taken to ensure that the measuring system is not influenced by environmental factors
such as:
— temperature variations;
— magnetic fields;
— surface finish;
— power source variations;
— transducer cable length;
— transducer orientation.
Particular attention should be given to ensure that the vibration transducers are correctly mounted
and that such mountings do not degrade the accuracy of the measurements.
The type and use of vibration instrumentation systems shall conform to ISO 2954 for housing vibration
measurement and shall conform to ISO 10817-1 for shaft vibration measurement. The instrumentation
should preferably include a facility for time and spectral frequency analysis.
5.1.2 Shaft measurement instrumentation
The recommended type of transducer for measuring relative shaft vibration is a non-contacting
transducer or proximity probe.
The instrument shall allow a reading of peak or peak-to-peak values of vibration displacement to be taken.
NOTE Shaft-riding transducers are no longer in common use, but if fitted, can be acceptable if the rotational
frequency of the shaft is less than 3 000 r/min, the signal frequency is less than 200 Hz, and surface rubbing
velocity is less than 30 m/s.
5.1.3 Housing measurement instrumentation
The recommended type of transducer for measuring housing vibration is a seismic transducer
measuring velocity or acceleration. In order to measure acceleration, velocity and displacement, it is
preferable to use an accelerometer. The instrumentation used to acquire the signal should be capable
of displaying the root-mean-square (RMS) values of vibration velocity in millimetres per second and
the true peak values of vibration acceleration in metres per second per second. The mounting method
can affect the frequency response of the transducer; it should therefore preferably be mounted with a
screw or stud or using a suitable bonding material. Magnet-mounted accelerometers can be acceptable
if the highest fundamental frequency of tooth meshing is less than 2 000 Hz. Hand-held housing
measurements are not acceptable for acceptance testing.
NOTE Information on mounting transducers is contained in ISO 5348 and ISO 13373-1.
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ISO 20816-9:2020(E)

5.2 Measurement frequency range
The instrumentation shall be capable of measuring from half the lowest shaft rotational speed to at
least 3,5 times the highest tooth mesh frequency.
The shaft displacement frequency measurement range shall be from 2 Hz to at least 500 Hz. The housing
velocity frequency measurement range shall be from 10 Hz to at least 2 000 Hz. The acceleration
frequency measurement range shall be from 10 Hz to 5 000 Hz. If a component rotational speed or tooth
meshing frequency occurs outside these ranges, revised frequency ranges shall be agreed between the
gear unit manufacturer and customer and/or operator.
5.3 Permissible errors
The measuring instrumentation system, including both the transducer and instrumentation, shall be
capable of indicating the vibration magnitude within a permissible error of ±10 % of the reading over
the entire operating frequency range.
NOTE Guidance on transducer selection is given in ISO 13373-1.
5.4 Calibration
For acceptance testing, the vibration instrumentation shall be checked against a reference signal and
any specified adjustments made immediately before and rechecked immediately after each series of
gear unit acceptance vibration measurements have been taken.
For in-situ measurements, calibration of the complete measuring equipment system should be carried
out regularly as specified by the instrumentation supplier. Calibrations are typically valid for one to
five years.
NOTE 1 Guidance on transducer calibration by comparison is given in ISO 16063-21.
NOTE 2 Guidance on transducer in-situ calibration is given in ISO 16063-44.
6 Vibration measurements
6.1 Shaft measurements
Vibration displacement of the shafts should be measured relative to the housing. Non-contacting
transducers (proximity probes) are normally used to measure radial vibration displacement, fitted in
orthogonal pairs through the journal bearing housing. Shaft vibration can also be measured axially,
especially when fluid-film thrust bearings are fitted. The number and location of transducers shall be
agreed between the gear unit customer and manufacturer. Guidance on mounting proximity probes is
given in ISO 10817-1.
Prior to running the gear unit up to its rated speed(s), slow-roll measurements of shaft displacement
may be carried out. If so, the measurement system needs to be capable of measuring down to low
frequencies (e.g. <5 Hz). Such measurements cannot normally be regarded as giving a valid indication of
shaft runout under normal operating conditions, since they can be affected by, for example, temporary
bows, erratic movements of the shaft within the bearing clearance, and axial movements. Subtraction of
slow-roll measurements from rated-speed vibration measurements should not be carried out without
careful consideration of these factors, since the results can provide a misleading interpretation of the
machine vibration.
The combined mechanical and electrical runout should not exceed 25 % of the allowable vibration
displacement at the shaft rotational frequency, or 6 µm, whichever is greater.
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ISO 20816-9:2020(E)

6.2 Housing measurements
Housing vibration shall be measured on a rigid housing section such as a bearing block. Measurements
should not be made on housing sections which do not support bearings or are not rigid, since they
will not provide a true indication of gear unit vibration. Measurements shall be taken in up to three
orthogonal directions, two of which lie in a plane perpendicular to the rotating axis of the gears. If
the load zone of the bearing is known, it is preferable to measure radially in this direction; otherwise
horizontal, vertical and axial are the preferred measurement directions. Axial measurements can give
additional information on faults such as gear misalignment and unbalance.
It is recommended that measurements be taken at each accessible bearing location on a gear unit. If a
bearing block is inaccessible, then the nearest mounting point may be used giving due consideration to
the transmission path from the bearing to this location. The number and location of transducers shall
be agreed between the manufacturer and customer and/or operator.
6.3 Units of measurement
The preferred units of measurement are given in Table 1.
Table 1 — Units of measurement
Quantity Unit
Displacement (peak-to-peak) µm
Velocity (RMS) mm/s
2
Acceleration (peak) m/s
Frequency Hz
7 Test conditions
7.1 General
The measurement of vibration on a gear unit can be conducted during:
a) manufacturer's shop test;
b) on-site acceptance testing;
c) in-service monitoring.
Special provisions can be required for vibration measurements in each case. The type of measurement
and acceptance values for each case should be agreed between the manufacturer and customer at an
early stage of negotiation.
7.2 Arrangement of the test system
7.2.1 Manufacturer's shop test
The mechanism for driving the gearbox during a shop test shall be the gear unit manufacturer's
responsibility unless otherwise negotiated with the customer and/or operator.
The test transmission, driver, gear unit and any load applied shall be connected by the in-service
couplings or by couplings with similar effective overhung masses. The gear unit can be tested with no-
load or with a light load to stabilize operation or in accordance with the conditions set out in 7.3.
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ISO 20816-9:2020(E)

7.2.2 On-site acceptance tests
On-site acceptance tests shall be carried out with the gear unit in the as-fitted, in-service configuration,
which shall be agreed between the gear unit manufacturer and customer and/or operator.
7.2.3 In-service monitoring
In-service monitoring shall be carried out with the gear unit in its in-service operating configuration,
to be agreed between the gear unit manufacturer and customer and/or operator.
7.3 Test conditions
The following test conditions shall apply, unless otherwise agreed between the gear unit manufacturer
and customer and/or operator:
a) the gear unit shall be tested at its intended in-service operating speed or, if designed for variable-
speed service, at the minimum, maximum and median values of its specified in-service speed range;
b) the gear unit shall be tested in its intended direction of rotation or, if reversible, in both directions;
c) the gear unit shal
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