ISO 20155:2017

INTERNATIONAL ISO
STANDARD 20155
First edition
2017-08
Ships and marine technology — Test
method of flow induced in-pipe noise
source characteristics for a ship-
used pump
Navires et technologie maritime — Méthode pour déterminer les
caractéristiques des sources de bruit induites par l’écoulement dans
les tuyaux d’une pompe de navire
Reference number
ISO 20155:2017(E)
©
ISO 2017

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ISO 20155:2017(E)

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© ISO 2017, Published in Switzerland
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ISO 20155:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Two-port source model and test method of source characteristic of pump .2
4.1 Two-port source model of a pump . 2
4.2 Test methods for source characteristic parameters of the pump . 3
5 Test rig . 4
5.1 Test loop . 4
5.2 Installation of test pump . 5
5.3 Ground foundation and supporting structure . 6
5.4 Test-bed pipeline . 6
5.5 Test section . 6
5.6 Throttling valve . 6
5.7 Secondary acoustic exciter . 7
5.8 Water tank. 7
6 Instrumentation . 7
6.1 General . 7
6.2 Static measurements. 7
6.3 Dynamic measurements . 7
7 Test preparation . 8
8 Test procedure . 8
9 Data processing . 9
9.1 General . 9
9.2 Passive characteristic of noise source . 9
9.3 Active characteristic . 9
10 Evaluation criteria for the test result . 9
11 Test report .10
11.1 Overview .10
11.2 General information .10
11.3 Test record .11
11.4 Test result .11
Annex A (informative) Theoretical models of a two-port source and transformation
mutually between matrix Z, S, T .13
Annex B (informative) Evaluation of quantities at inlet and outlet ports.15
Annex C (informative) Judgment of effectiveness for the test .17
Annex D (informative) Formulae for determining passive characteristics of noise source .19
Annex E (informative) Formulae for determining active characteristics of source .20
Annex F (informative) Verification of test method taking a T-shaped sound excitor as a two-
port acoustic source .21
Bibliography .24
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ISO 20155:2017(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/ directives).
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
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 8, Ship design.
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ISO 20155:2017(E)

Introduction
In hydraulic fluid power systems of ships, power is transmitted through a liquid under pressure.
Pumps are components that convert rotary mechanical power into hydraulic fluid power. During the
process of converting mechanical power into hydraulic power, flow and pressure fluctuations and
structure-borne vibrations are generated. These fluid-borne and structure-borne vibrations, which
are generated primarily by the unsteady flow produced by the pump, are transmitted through the
connected piping system.
The fluid-borne vibration generated by a pump is called pressure ripple or flow induced noise. For
pumps used for coolant and drainage in ships, flow induced noise can be transmitted along the piping
and radiated into the surrounding water area through a pipe mouth outboard the ship, which produces
noise pollution and disturbs the environment including marine mammals.
The level of flow induced noise for a pump depends upon not only the characteristics of the pump itself,
but also the circuit in which the pump is installed. Thus, the determination of flow induced noise by
a pump is complicated by the interaction between the pump and the circuit. The directly measured
data using hydrophones inserted in pipe reaches connecting the pump cannot reflect noise source
characteristics of the pump. The method adopted to measure the flow induced noise of a pump should
be such as to eliminate the interaction.
ISO 10767-1 and ISO 10767-2 provide the test methods for the positive displacement pump with the
precision and simplified method, respectively, where the pump is treated as a single port acoustic
source and its source characteristics expressed by two parameters of source strength as well as source
impedance can be obtained. For other common pumps with two ports, the sound field between the
inlet and outlet of a pump is inter-coupling, source characteristics cannot be fully expressed by two
parameters, but expressed by up to six parameters, i.e. source pressures at the inlet and outlet of a
pump and four elements in a 2 × 2 impedance matrix. There is a need to establish a new standard about
a test method for noise source characteristics of a pump, based on two-port acoustic source model.
The source characteristics of flow induced noise are used for evaluating the hydrodynamic noise feature
of the pump. The measured results can be compared for pumps of different types and manufacture.
This will enable the pump designer to evaluate the effects of design modifications and help hydraulic
system designers to avoid selecting pumps having high noise levels.
The method is based upon the application of plane wave transmission line theory to the analysis of
noise propagation in hydraulic systems. By adopting a two-port model with noise source and evaluating
the impedance characteristics of the pump using a secondary-source method, it is possible to obtain the
source strength of the pump, independent of the circuit that the pump locates.
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INTERNATIONAL STANDARD ISO 20155:2017(E)
Ships and marine technology — Test method of flow
induced in-pipe noise source characteristics for a ship-
used pump
1 Scope
This document specifies a test method for determining flow induced in-pipe noise source characteristics
of a ship-used pump as a two-port sound source in laboratory conditions by measuring acoustic
pressures in the pipe reaches of inlet and outlet.
The test method is applicable to all types of centrifugal pumps with a diameter over 50 mm operating
under steady conditions.
The suitable frequency range of the test method is about 10 Hz to 1 000 Hz, and the upper frequency is
dependent on the inner diameter of the pipe, in which the plane acoustic wave propagates.
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.
ISO 10767-1:2015, Hydraulic fluid power — Determination of pressure ripple levels generated in systems
and components — Part 1: Method for determining source flow ripple and source impedance of pumps
IEC 60565, Underwater acoustics — Hydrophones — Calibration in the frequency range 0,01 Hz to 1 MHz
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
two-port source
test object with inlet and outlet which are inter-coupling acoustically
3.2
passive characteristic
acoustic characteristic of a test object only acting as a transmission path, which can be indicated by
different manners such as a transfer matrix, impedance matrix, scattering matrix, etc.
3.3
active characteristic
acoustic characteristic of a test object which provides acoustic energy into a piping system
Note 1 to entry: Depending on the adopted theoretical model, active characteristics can be represented by
acoustic pressure source, volume velocity source, etc.
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ISO 20155:2017(E)

3.4
test section
pipe reaches which are used to fix the hydrophones, measuring the in-pipe noise from the acoustic source
3.5
static pressure in pipe
fluid pressure in pipe as fluid is in still, which is one of the parameters describing the working conditions
of the test object
3.6
working flowrate
fluid volume or mass per unit time, which is one of the working parameters of the test object
3.7
pressure drop/hydraulic loss
static pressure difference between the inlet and outlet as the fluid passes through the test object, which
is a reference parameter for analysis use
3.8
foundation
platform built by ferroconcrete, used to install the experimental facility and test objects, including
ground basis, guide rail for convenient mount of pipeline
4 Two-port source model and test method of source characteristic of pump
4.1 Two-port source model of a pump
It is assumed that only plane wave would transmit in the pipeline, and the noise source characteristic
of a pump could be described by linear superposition of active and passive characteristic. Based on
the electro-acoustic analogy and acoustic transmission line theory, there are three different models
to characterize a two-port source, which can be called “Transmission model”, “Impedance model” and
“Scattering model”. They are illustrated in Annex A.
4 5
13
P , Q P , Q P , Q
s s o o
i i
p p
so
si
2
Key
1 flow
2 source
3 pipe
4 inlet
5 outlet
Figure 1 — Two-port noise source model
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ISO 20155:2017(E)

Adopting the impedance model, the radiating sound from the inlet and outlet into pipe can be expressed
by Formula (1):
P  ZZ Q  P  Q  P 
 
o 11 12 o so o so
 =  + =Z +  (1)
 
         
P ZZ Q P Q P
 
i  21 22 i si i si
         
where
is the real sound source of a pump providing sound pressure and volumetric velocity into
PQ,
ss
the inlet and outlet of the pump, while the connected pipes are unlimited or anechoic;
is the sound pressure and volumetric velocity at the outlet of acoustic source,
PQ,
oo
respectively;
is the sound pressure and volumetric velocity at the inlet of acoustic source,
PQ,
ii
respectively;
is the sound pressure source which indicate radiating sound from the inlet and outlet
PP,
so si
into pipe;

ZZ
 
11 12
Z is the impedance matrix, Z = .
 
ZZ
 
 21 22
4.2 Test methods for source characteristic parameters of the pump
Using the secondary-source method, turn on the secondary acoustic source on one side (inlet or outlet),
get and register signals from the four hydrophones. Then, move it to another side and turn it on, register
signals of the four hydrophones again. By this procedure, matrix parameter Z can be derived. Finally,
turn off the source, active characteristic parameters p and q of the pump can be obtained utilizing
s s
the result of matrix parameter Z.
Key
1 secondary source 1
2 secondary source 2
3 test pump
4 hydrophones H to H
1 6
Figure 2 — Sketch of dual-position acoustic source methods
In Figure 2, H to H are six hydrophones along the pipe mounted at positions x to x , correspondingly.
1 6 1 6
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ISO 20155:2017(E)

The procedure for measuring source characteristics is given as follows.
a) Turn on the secondary acoustic source at the inlet for the following result:
()1 ()1
   
P Q
ZZ 
o o
11 12
   
= (2)
 
 ()1   ()1 
ZZ
 
 21 22
P Q
 i   i 
(1)
where superscript indicates the corresponding quantities obtained by turning on the secondary
sound source at the first time, and they can be obtained by means of calculation using formulae in
Annex B, which correlate the quantities with the measured signals from hydrophones.
b) Turn on the secondary acoustic source at the outlet for the following result:
()2 ()2
   
P Q
ZZ 
o 11 12 o
   
= (3)
 
 ()2   ()2 
ZZ
 
P  21 22 Q
 i   i 
(2)
where superscript indicates the corresponding quantities obtained by turning on the secondary
sound source at the second time.
c) Combine Formulae (2) and (3) and solve the equation system, the impedance matrix Z can be
calculated.
()12() (112)( )
   
PP  ZZ Q Q
 
oo 11 12 o o
   
= (4)
 
 ()12()   ()12() 
ZZ
 
PP   21 22 QQ
 ii   ii 
d) Turn off the secondary acoustic source, and let the measured pump operate under the needed
conditions, the active source parameters, i.e. sound pressure source PP, can be obtained
so si
according to Formula (5).
P  P  ZZ Q 
 
so o 11 12 o
 = −   (5)
 
     
P P ZZ Q
 
si i  21 22 i
     
At the right side of Formula (5), P , P and Q , Q are obtained by calculation using the measured
o i o i
signals from hydrophones during pump operation.
5 Test rig
5.1 Test loop
Figure 3 shows the schematic of test circuit of flow induced in-pipe noise source characteristic of
the pump.
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ISO 20155:2017(E)

Key
1 pump 6 water tank
2 hydrophone 7 flexible insertion
3 vibration 8 vibroisolator
4 secondary acoustic excitor 9 foundation
5 throttling valve
Figure 3 — Sketch of test circuit for measuring flow-noise source characteristic of the pump
In the schematic diagram, a water tank is used for separating sound waves from the inlet and outlet
of pump. A throttling valve is used for flowrate adjustment and located between the water tanks for
reducing the effect on source characteristic measurement of the pump. A secondary acoustic exciter
can provide an external acoustic source for determination of passive features of the pump, and the
vibration damper can suppress the vibration of the test section from the neighbouring pipe reaches.
Hydrophones are mounted in test sections at the inlet and outlet of the pump for measuring the acoustic
pressure in the pipeline.
5.2 Installation of test pump
The test pump should be installed as recommended by the manufacturer and mounted in such a manner
that the response of the mounting-to-pump vibration is minimized.
In order to reduce vibration disturbance from the ground and the connected pipe, the pump should
be installed on the foundation through vibration isolators and connected to the pipeline with flexible
insertions. The isolators and flexible insertions should be chosen close to the actual conditions.
The prime mover and associated drive couplings shall not generate torsional vibration in the pump
shaft. If necessary, the pump and the driving unit shall be isolated from each other to eliminate vibration
generated by the prime mover.
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ISO 20155:2017(E)

5.3 Ground foundation and supporting structure
Ground foundation should be made of reinforced concrete and isolated to the surrounding ground in
the laboratory such as foundations of other auxiliary equipment. A supporting structure of the pipeline
is also required to be rigidly connecting the pipeline with the ground foundation.
5.4 Test-bed pipeline
The pipeline shall be composed of uniform, rigid, straight metal pipes at each port of the pump.
The inner diameters of the test pipeline at inlet and outlet should be equal to that of the inlet and outlet
of the test pump respectively. In the case of the inequality of inner diameter between the test pump
and pipeline, the adaptor connecting the pump ports to the pipe shall have an internal diameter which
does not differ from the pipe diameter by more than 10 % at any point. Any such variations in internal
diameter shall occur over a length not exceeding twice the internal diameter of the pipe. The adaptor
shall be arranged in order to prevent the formation of air pockets in it.
The bending section in the pipeline of Figure 3 shall adopt bends with bending radii larger than twice
the radii of the pipe to reduce hydrodynamic noise arising from the flow over it.
The total length of the uniform straight pipeline in front of the inlet flange of the test pump should be
10 times larger than pipe diameter.
5.5 Test section
Each of the two test sections as a straight pipe reach is fixed on the inlet and outlet of the test pump
respectively, with the length more than 2 m, the inner diameters, D, equal to that of inlet and outlet
pipe of the test pump. The test section should be fabricated with a tube of wall thickness greater than
5 % of the inner diameters, D. In the test section, two or three hydrophones with equal interval are
fixed on the pipe. Each hydrophone is put in a plug mounted on the pipe. In order to reduce interference
from turbulence over the inner wall of the pipe, the hydrophones shall be mounted such that their
diaphragms are flush with the inner wall of the pipe to within ±0,5 mm. The sealing ring in the plug
should be used between the hydrophone and plug body to prevent water leakage.
The distance between two or two of three hydrophones depends on the maximum frequency of the
measurement frequency range and shall be given by Formula (6), to within 1 %:
5
B ×10 /ρ
eff
xx−= (6)
21
()67× f
0,max
where

is the maximum frequency of the measurement frequency range, in hertz;
f
0,max

is the effective bulk modulus, in bars;
B
eff
ρ is the density, in kilograms per cubic meter.
Meanwhile, in order to avoid turbulent fluctuation pressure from the pump impacting directly on
hydrophone, the nearest hydrophone should be positioned at a distance larger than 3 to 5 times pipe
inner diameter from the test pump.
5.6 Throttling valve
The throttling valve should meet the need of flowrate adjustment. From the point of acoustic
measurement, it should have a low noise level and no cavitation should appear under the test working
conditions.
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ISO 20155:2017(E)

5.7 Secondary acoustic exciter
The secondary acoustic exciter is composed of a vibration exciter of electromagnetic type and a piston
with a bar connecting them. The piston is driven by the exciter and produces acoustic plane waves by
its oscillatory motion in the working medium. The intensity of acoustic waves should be 10 dB higher
than the background noise in the frequency spectrum to ensure sufficient signal-noise-ratio.
5.8 Water tank
A water tank should have a volume at least 30 times the connected pipeline.
6 Instrumentation
6.1 General
The source characteristic test of a pump includes a static and dynamic measurement. A static
measurement is mainly used to define working parameters of the pump. A dynamic measurement is
used to collect sound pressure signals generated by the test pump radiating into the pipeline.
6.2 Static measurements
In static measurement, some quantities should be measured, which include flowrate and static pressure
of fluid in the pipe, shaft rotational speed of pump and pressure drop across the pump, temperature of
working medium, etc.
The requirement of instrumentation for static measurements shall be in accordance with
ISO 10767-1:2015, 4.1.
6.3 Dynamic measurements
The instruments for dynamic measurements consist of a transducer, a signal conditioner and data
acquisition or signal analyser. A hydrophone is used to measure the sound pressure in the pipe. A charge
amplifier or measuring amplifier is chosen as a signal conditioner.
Transducers shall be chosen to meet the requirements for working in the allowable environment (such
as static pressure, temperature, magnetic field, anti-corrosion, etc.) and needed frequency range. The
natural frequency of the hydrophone shall be higher than 30 kHz and nonlinearity less than ±1 %. In
the test frequency range, the amplitude inhomogeneity of hydrophone should be less than 0,2 dB, and
the inhomogeneity of phase frequency characteristic less than 0,5°.
Figure 4 shows the schematic diagram of dynamic measurement system.
Key
1 hydrophone
2 charge/measuring amplifier
3 data acquisition or signal analyser
4 computer
Figure 4 — Schematic diagram of dynamic measurement system
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ISO 20155:2017(E)

A Piezoelectric mini-type hydrophone can be adopted. The hydrophone outputs the charge, which is
imported into the data acquisition or signal analyser. With the computer, a signal can be recorded and
analysed. Using the post-processing analysis software, final results can be obtained.
Hydrophones shall be calibrated in accordance with the requirements of IEC 60565.
7 Test preparation
A test circuit should be assembled with a layout shown in Figure 3. Each component of a test circuit
shall be chosen, designed, and mounted according to requirements described in Clause 5.
Each two or three hydrophones shall be install
...