ISO 18312-1:2012
(Main)Mechanical vibration and shock — Measurement of vibration power flow from machines into connected support structures — Part 1: Direct method
Mechanical vibration and shock — Measurement of vibration power flow from machines into connected support structures — Part 1: Direct method
This part of ISO 18312 specifies a method for evaluating the vibration power emitted by machines or pipelines, referred to hereinafter as machines, under operational conditions on to supporting structures to which the machines are directly connected via bolted joints. This part of ISO 18312 specifies the method for evaluating the vibration power components emitted in the six degrees of freedom of a Cartesian coordinate system at each joint, i.e. three translations and three rotations. The vibration power is determined by processing the signals from force and velocity (or acceleration) transducers mounted on to the bolted joints under operational conditions of interest. This method is applicable for machines under the assumption that their vibration can be characterized by a stationary random process. The components of emitted vibration power in the frequency domain are obtained by computing the cross‑spectrum of the force and velocity measurement pairs with a given narrow band width at each bolted joint. This direct method assumes that the supporting structures are adequately rigid and, hence, it is not applicable to cases where the foundation or supporting structures are resilient, which will potentially go into a state of resonance within the frequency range of interest. Practical frequency limits of the method are specified in this part of ISO 18312. This part of ISO 18312 can be used in operational conditions for: a) specification of vibration power emission of machines at the (bolted) joints; b) identification of vibration power severity; c) resolving diagnostics issues; d) planning vibration control measures.
Vibrations et chocs mécaniques — Mesurage du flux de puissance vibratoire transmis par des machines aux structures de support dont elles sont solidaires — Partie 1: Méthode directe
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 18312-1
First edition
2012-01-15
Mechanical vibration and shock —
Measurement of vibration power flow
from machines into connected support
structures —
Part 1:
Direct method
Vibrations et chocs mécaniques — Mesurage du flux de puissance
vibratoire transmis par des machines aux structures de support dont
elles sont solidaires — Partie 1: Méthode directe
Reference number
ISO 18312-1:2012(E)
©
ISO 2012
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ISO 18312-1:2012(E)
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ii © ISO 2012 – All rights reserved
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ISO 18312-1:2012(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Fundamentals . 3
5 Measurement . 5
5.1 General . 5
5.2 Arrangement of vibration transducers . 5
5.3 Measurement of forces . 5
5.4 Measurement equipment . 7
5.5 Metrological specifications . 8
5.6 Determination of upper frequency limit . 9
5.7 Choice of number of joints to measure from . 9
5.8 Determination of total vibration power by measuring from a limited number of joints . 9
6 Measurement uncertainty .10
7 Data presentation and test report .10
Bibliography .12
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ISO 18312-1:2012(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.
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 18312-1 was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and condition
monitoring.
ISO 18312 consists of the following parts, under the general title Mechanical vibration and shock — Measurement
of vibration power flow from machines into connected support structures:
— Part 1: Direct method
— Part 2: Indirect method
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INTERNATIONAL STANDARD ISO 18312-1:2012(E)
Mechanical vibration and shock — Measurement of vibration
power flow from machines into connected support structures —
Part 1:
Direct method
1 Scope
This part of ISO 18312 specifies a method for evaluating the vibration power emitted by machines or pipelines,
referred to hereinafter as machines, under operational conditions on to supporting structures to which the
machines are directly connected via bolted joints. This part of ISO 18312 specifies the method for evaluating
the vibration power components emitted in the six degrees of freedom of a Cartesian coordinate system at
each joint, i.e. three translations and three rotations. The vibration power is determined by processing the
signals from force and velocity (or acceleration) transducers mounted on to the bolted joints under operational
conditions of interest. This method is applicable for machines under the assumption that their vibration can be
characterized by a stationary random process.
The components of emitted vibration power in the frequency domain are obtained by computing the
cross-spectrum of the force and velocity measurement pairs with a given narrow band width at each bolted joint.
This direct method assumes that the supporting structures are adequately rigid and, hence, it is not applicable
to cases where the foundation or supporting structures are resilient, which will potentially go into a state of
resonance within the frequency range of interest. Practical frequency limits of the method are specified in this
part of ISO 18312.
This part of ISO 18312 can be used in operational conditions for:
a) specification of vibration power emission of machines at the (bolted) joints;
b) identification of vibration power severity;
c) resolving diagnostics issues;
d) planning vibration control measures.
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, Mechanical vibration, shock and condition monitoring — Vocabulary
ISO 5348, Mechanical vibration and shock — Mechanical mounting of accelerometers
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2041 and the following apply.
3.1
vibration velocity vector
n
v
velocity vector at the nth bolt joint, consisting of three translational and three rotational components along the
coordinate axes x, y and z
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ISO 18312-1:2012(E)
3.2
vibration velocity component
n
v
i
component of the vibration velocity vector in the degree of freedom i at the nth bolted joint; i = 1, 2 and 3 for
linear components in the x-, y-, and z-directions, respectively, and i = 4, 5 and 6 for angular components in the
x-, y- and z-directions, respectively
3.3
vibration acceleration component
n
a
i
vibration acceleration component in the degree of freedom i at the nth bolted joint
3.4
root mean square value of acceleration component
r.m.s. value of acceleration component
n
a
i:rms
root mean square value of the vibration acceleration component in the degree of freedom i at the nth bolted joint
3.5
force vector
n
F
vibration force vector at the nth joint, consisting of three components of linear force and three components of
angular force, i.e. moment, along the coordinate axes x, y and z
3.6
force component
n
F
i
component of the vibration force vector in the degree of freedom i at the nth joint; i = 1, 2 and 3 for force
components in the x-, y- and z-directions, respectively, and i = 4, 5 and 6 for moment components in the x-,
y- and z-directions, respectively
3.7
vibration power component
n
P
i
vibration power in the degree of freedom i at the nth bolted joint, equal to the time-averaged scalar product of
the vibration force vector and vibration velocity vector in the degree of freedom i at the nth bolted joint
Note to entry: A vibration power component is expressed in watts.
3.8
vibration power at a joint
n
P
vibration power at the nth bolted joint, equal to the sum of the vibration power components in each degree of
freedom at that point
3.9
vibration power
P
sum of vibration power of the machine over all joints and in every degree of freedom
3.10
vibration power spectrum
P(f, Δf)
decomposition of the vibration power of the machine into frequency domain with a given centre frequency, f, narrow
frequency band, Δf, equal to the sum of the vibration power spectra over all joints and in every degree of freedom
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ISO 18312-1:2012(E)
3.11
component of vibration power spectrum
n
Pf ,Δf
()
i
spectrum of the vibration power transmitted in the degree of freedom i at the nth joint
3.12
vibration power spectrum at a joint n
n
Pf ,Δf
()
spectrum of the vibration power transmitted at the nth joint
3.13
component of vibration power cross spectrum
n
Gf
()
Fv
ii
cross spectrum of a vibration force component, F (t), and a vibration velocity component, v (t), in the degree of
i i
freedom i at the nth joint
3.14
vibration power level
P
L =10lg dB
W
P
0
common logarithm of the ratio of measured vibration power to the reference value, P = 1 pW, corresponding
0
to zero level of vibration power
4 Fundamentals
The layout of a machine bolted directly on to the foundation structure at multiple joints is shown in Figure 1 and
the detail of a bolted joint is shown in Figure 2 together with a coordinate system, where the z-axis is chosen
in parallel with the bolt axis.
Key
1 machine
2 bolted joints
3 foundation
Figure 1 — Layout of machine bolted on to foundation directly at multiple joints
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ISO 18312-1:2012(E)
Key
1 machine leg
2 bolt
3 nut
4 foundation flange
Figure 2 — Coordinate system of a bolted joint
Vibration power emitted by the machine on to the foundation via the nth bolted joint is defined as the time
average of scalar product of the force vector and velocity vector as follows:
L L L
6 6
11 1
nn n n n n n
P = Fvtt⋅ ddt = Ft vt t = Ft v tttd (1)
() () () () () ()
∑ i i ∑ i i
∫ ∫ ∫
L L L
i=1 i=1
0 0 0
where the term within the summation on the most right hand side
L
1
n n n
Ft vt dtP≡
() ()
i i i
∫
L
0
denotes vibration power emitted in the degree of freedom i at the nth joint with the index i = 1 to 3 denoting the
linear or translational degrees of freedom and the index i = 4 to 6 denoting the angular or rotational degrees of
freedom. The record length L in Equation (1) shall be far greater than the fundamental period of the measured
signals. In practice, contributions of the rotational components in Equation (1) due to angular velocities and
moments may be omitted when difficulty of measurements exists. The total vibration power emitted by a
machine with multiple bolted joints on to the support structure can be obtained just by summing up the vibration
power transmitted via each bolted joint in Equation (1). Vibration power is a scalar quantity and, hence, the total
vibration power emitted from a machine with a number of bolted joints, K, is given simply by a sum:
K
n
PP= (2)
∑
n=1
n
The vibration power in the ith degree of freedom at the nth joint, P , can be resolved into the frequency domain
i
n n
by taking real parts of the cross power spectrum Gf ,Δf from the force signal Ft and velocity signal
() ()
i
Fv
ii
n
vt using a commercial signal analyser as follows:
()
i
n n
Pf,RΔΔfG= e,ff (3)
() ()
i
Fv
ii
n n
where Re[•] denotes the real part of a complex quantity • and the unit of Pf,RΔΔfG= e,ff is watt
() ()
i
Fv
ii
at a centre frequency, f, over a narrow frequency band, Δf, e.g. 1 Hz when the units of the force and velocity
n
are newton and metre per second, respectively. If acceleration at in metre per second squared is measured
()
i
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ISO 18312-1:2012(E)
n
instead of the velocity vt() in metre per second, the vibration power in Equation (3) is given in a slightly
i
different format as follows:
1
n n
Pf,IΔf = m,Gf Δf (4)
() ()
i
Fa
ii
2πf
where Im[•] denotes the imaginary part of the complex quantity •. The sum of the vibration power over
frequencies, degrees of freedom, and all the mounts of interest can now be easily calculated. When a partial
vibration power over a specific frequency range of interest, in hertz, e.g. from f to f is of interest, it can
min max
n
be obtained simply by summing the vibration power spectrum Pf ,Δf in Equation (3) or (4) as follows:
()
i
N
n n
Pf()~,fP=+fk()−1 ΔΔff (5)
{}
i minmax ∑ i min
k=1
where N is the number of frequency points over the frequency range of interest given by
ff−
maxmin
N =
Δf
in case of a narrow frequency band analysis. Once the vibration power spectrum is available in a narrow band
from Equations (3) and (4), the vibration power spectrum over one-third octave band or other octave bands can
be obtained by simply summing over the bandwidths of interest.
5 Measurement
5.1 General
This part of ISO 18312 specifies how to evaluate the vibration power transmitted by a machine on to its
foundation from the measurement of forces and vibration at the bolted joints. Such measurements are not limited
to translational degrees of freedom, but may be extended to rotational degrees of freedom, depending upon the
capabilities of the employed transducers. This clause explains how to install the vibration and force transducers.
5.2 Arrangement of vibration transducers
One multi-axial vibration transducer is placed on a joint bolt head as shown in Figures 3 an
...
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