ISO 20283-4:2012

INTERNATIONAL ISO
STANDARD 20283-4
First edition
2012-04-15
Mechanical vibration — Measurement of
vibration on ships —
Part 4:
Measurement and evaluation of vibration
of the ship propulsion machinery
Vibrations mécaniques — Mesurage des vibrations à bord des navires —
Partie 4: Mesurage et évaluation des vibrations des machines de
propulsion des navires
Reference number
©
ISO 2012
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ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vibration tests . 3
4.1 Instrumentation . 3
4.2 Test conditions . 3
4.3 Test procedure . 4
4.4 Data processing . 5
4.5 Measurements . 5
5 Evaluation criteria .14
6 Test report .15
Annex A (informative) Manoeuvring, transient measurements .16
Annex B (informative) Evaluation of vibration at mechanical azimuth drives (e.g. Schottel rudder
propellers) and shaft lines by measurements on non-rotating parts .17
Annex C (informative) Evaluation of the vibration of a Voith−Schneider propeller by measurements on
non-rotating parts.18
Bibliography .20
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 20283-4 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.
ISO 20283 consists of the following parts, under the general title Mechanical vibration — Measurement of
vibration on ships:
— Part 2: Measurement of structural vibration
— Part 3: Pre-installation vibration measurement of shipboard equipment
— Part 4: Measurement and evaluation of vibration of the ship propulsion machinery
The following part is planned:
— Part 1: General guidelines
iv © ISO 2012 – All rights reserved

Introduction
In general, classification societies ask for a numerical study on the torsional vibration behaviour of the propulsion
system for seagoing vessels at the design stage as a base for the design approval. Depending on the results
of this study and the kind of plant to be considered, further torsional vibration investigations for verification on
a case-by-case study may be required. Explicit criteria for the evaluation of the torsional loadings are given
within the rules of the international classification societies as well as in the form of unified requirements (UR)
[10]
of the International Association of Classification Societies, specifically IACS UR M68, with focus on the
torque transmitting parts, such as shafts, gears, couplings, and connections. Studies of the bending vibration
behaviour of the shaft as well as axial vibration of the propulsion system or crankshaft may be required by the
classification societies in the exceptional case that the special design of the system makes such additional
investigations necessary.
Propulsion systems may be exposed to vibration of high magnitude in general excited by the engine
and/or propeller. In addition to the numerical criteria for evaluation of torsional vibration, some further special
requirements may be raised, such as avoiding load reversal in the transmission train. In general, mechanical
components may be perfectly designed for load reversal operation; however, some specific requirements in
this direction are also based on smooth operation of the plant, and the owners or managers of special vessels
such as navy ships or yachts consequently raise them.
The user of this part of ISO 20283 should bear in mind that for the evaluation of measured data on propulsion
plants of ships the rules of the responsible classification society for the vessel in their latest edition or the valid
IACS UR should be considered.
Should any issues regarding this part of ISO 20283 be directly or indirectly addressed by the contracted
classification society’s rules or other international binding regulations, such as those of the International
Maritime Organization (IMO), the International Convention for the Safety of Life at Sea, and UK Maritime
and Coastguard Agency, the choice of the measuring method applied should fulfil the sense of these rules or
regulations, independently of whether the special measuring method is specified within this part of ISO 20283.
INTERNATIONAL STANDARD ISO 20283-4:2012(E)
Mechanical vibration — Measurement of vibration on ships —
Part 4:
Measurement and evaluation of vibration of the ship
propulsion machinery
1 Scope
This part of ISO 20283 provides guidelines for the instrumentation, measurement, and data processing
procedures required to obtain reliable vibration data on ship propulsion systems. It also gives guidelines for the
application of specific measuring techniques, which are common and adequate for measuring the mechanical
vibration on propulsion plants of seagoing and inland vessels. The measuring techniques can be applied
to diesel engine as well as turbine or electrically driven plants, always considering the specific limitation of
application of each individually described procedure.
The procedures specified in this part of ISO 20283 focus on repetitive mechanical vibration (steady-state or
quasi-stationary like a sweep) and can therefore be inadequate for measuring and evaluating transient, very
fast-changing or shock signals.
This part of ISO 20283 mainly specifies techniques for measuring the mechanical vibration of the main propulsion
plant during sea trials. The same or similar measuring principles can also be used for other purposes, such
as performance monitoring, investigations of abnormal vibration in service, and evaluation of the condition
of repaired parts. However, in such cases, the measuring procedure needs to be adapted to the specific
requirements.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable
for its application. For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
ISO 2041:2009, Mechanical vibration, shock and condition monitoring — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2041 and the following apply.
3.1
free route
condition achieved when the ship is proceeding at a constant speed and course with helm adjustment of ±2°
or less and no throttle adjustment
[SOURCE: ISO 20283-2:2008, 3.3]
3.2
vibration severity
value, or set of value, such as maximum value, average or r.m.s. value, or other parameters that are descriptive
of the vibration, referring to instantaneous values or to average values
[SOURCE: ISO 2041:2009, 2.51]
Note 1 to entry: The vibration severity is a generic term, which in the past has been used in relation to vibration velocity.
However, it is now more generally used as descriptive of other measurement units, such as displacement and acceleration.
3.3
peak value
maximum value of a vibration during a specified time interval
[SOURCE: ISO 2041:2009, 2.44]
Note 1 to entry: A peak value is usually taken as the maximum deviation of that vibration from the mean value. A positive
peak value is the maximum positive deviation and a negative peak value is the maximum negative deviation, see Figure 1.
Note 2 to entry : In vibration, usually the peak value is understood as half of the peak-to-peak value (of a
vibration) since positive and negative peak values can be different, see also 3.4.
3.4
peak-to-peak value
〈vibration〉 difference between the maximum positive and maximum negative values of a vibration during a
specified interval
[SOURCE: ISO 2041:2009, 2.45]
Note 1 to entry: See Figure 1.
3.5
r.m.s. value
〈vibration〉 root mean square value (computed by the square root of the sum of the squares of the magnitude) of
a fast Fourier transform spectrum with a defined bandwidth or of a time signal during a specified time interval
(e.g. a period of the fundamental frequency)
EXAMPLE 1 An r.m.s. value within a time interval t to t
1 2
t
ut()dt
∫
tt−
t
EXAMPLE 2 An r.m.s. value from a fast Fourier transform (FFT) spectrum with N spectral lines
N
X
∑
n
n=1
See Figure 1.
Note 1 to entry: This definition of r.m.s. value of a spectrum is derived from the more general definition of r.m.s. spectrum
in ISO 2041:2009, 5.11, adapted to the common use in vibration.
Note 2 to entry: For sine waves, the r.m.s. value is the peak value divided by √2.
Note 3 to entry: In case of mixed source excitation, windowing should be applied. Additional factors need to be included,
to give an r.m.s. value of the form:
N
X
∑
n
2B
n=1
where
B is the window noise bandwidth factor depending on the anti-leakage window:
B = 1,5 for a Hanning window,
B = 3,77 for a flat top window,

B = 1 without an anti-leakage window;
X is the narrow band magnitude obtained by FFT.
n
2 © ISO 2012 – All rights reserved

Key

1 peak value, u
 
2 peak-to-peak value, from −u to +u
3 r.m.s. value
4 period duration
Figure 1 — Values of a vibration u(t) (simplified for a sine wave)
4 Vibration tests
4.1 Instrumentation
The transducers, the signal conditioning, and data storage equipment shall be capable of performing accurate
measurements in the frequency range, which is adequate for the vibration quantities to be measured. The
applied measurement techniques should be able to maintain an accuracy of ±10 %. The involved parties,
namely the yard or builder, owner, class, and supplier, should define a suitable frequency range for the
measurements, depending on the mechanical quantity to be measured. As a general guideline, for linear
vibration measurements, an upper frequency limit of 1 000 Hz is normally used and sufficient. For strain gauge
measurements of forces or torques or other measurements on the rotating parts of the propulsion system,
an upper frequency limit of 100 Hz for low-speed two-stroke engines and of 400 Hz for four-stroke engines
is sufficient (for four-stroke engines at least the upper frequency has to come up to the product of maximum
rotational speed by number of cylinders). For acceleration measurements on gearboxes, higher frequencies,
depending o
...