SIST EN ISO 13350:2009
(Main)Industrial fans - Performance testing of jet fans (ISO 13350:1999)
Industrial fans - Performance testing of jet fans (ISO 13350:1999)
This International Standard deals with the determination of those technical characteristics needed to describe all aspects of the performance of jet fans as defined in ISO 13349. It does not cover those fans designed for ducted applications, nor those designed solely for air circulation, e.g. ceiling fans and table fans.
The test procedures described in this International Standard relate to laboratory conditions. The measurement of performance under on-site conditions is not included.
Einführendes Element - Haupt-Element - Ergänzendes Element (ISO 13350:1999)
Diese Internationale Norm befasst sich mit der Bestimmung jener technischen Leistungskenngrößen, die für
die Beschreibung aller Leistungsmerkmale von Strahlventilatoren notwendig sind, wie in ISO 13349 festgelegt.
Nicht abgedeckt werden Ventilatoren, die für einen Anschluss an Rohrleitungen konstruiert wurden und
Ventilatoren, die ausschließlich der Luftzirkulation dienen, wie z. B. Decken- und Tischventilatoren.
Die in dieser Internationalen Norm beschriebenen Prüfverfahren beziehen sich auf Laborbedingungen. Die
Leistungsmessung unter Bedingungen vor Ort ist nicht Bestandteil dieser Norm.
Ventilateurs industriels - Essai de performance des ventilateurs accélérateurs (ISO 13350:1999)
La présente Norme internationale traite de la détermination des caractéristiques techniques qui sont nécessaires pour décrire tous les aspects de la performance des ventilateurs accélérateurs tels que définis dans l'ISO 13349. Elle ne couvre pas les ventilateurs destinés aux applications en conduit ni ceux destinés uniquement à la circulation de l'air, par exemple les ventilateurs de plafond et de table. Les procédures d'essai décrites dans la présente norme concernent les conditions de laboratoire. La mesure de la performance sur site n'est pas incluse.
Industrijski ventilatorji - Mehanska varnost odprtih ventilatorjev (ISO 13350:1999)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 13350:2009
01-maj-2009
Industrijski ventilatorji - Mehanska varnost odprtih ventilatorjev (ISO 13350:1999)
Industrial fans - Performance testing of jet fans (ISO 13350:1999)
Einführendes Element - Haupt-Element - Ergänzendes Element (ISO 13350:1999)
Ventilateurs industriels - Essai de performance des ventilateurs accélérateurs (ISO
13350:1999)
Ta slovenski standard je istoveten z: EN ISO 13350:2008
ICS:
23.120 =UDþQLNL9HWUQLNL.OLPDWVNH Ventilators. Fans. Air-
QDSUDYH conditioners
SIST EN ISO 13350:2009 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 13350:2009
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SIST EN ISO 13350:2009
EUROPEAN STANDARD
EN ISO 13350
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2008
ICS 23.120
English Version
Industrial fans - Performance testing of jet fans (ISO
13350:1999)
Ventilateurs industriels - Essai de performance des
ventilateurs accélérateurs (ISO 13350:1999)
This European Standard was approved by CEN on 2 October 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13350:2008: E
worldwide for CEN national Members.
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SIST EN ISO 13350:2009
EN ISO 13350:2008 (E)
Contents Page
Foreword.3
2
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SIST EN ISO 13350:2009
EN ISO 13350:2008 (E)
Foreword
The text of ISO 13350:1999 has been prepared by Technical Committee ISO/TC 117 “Industrial fans” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 13350:2008 by
Technical Committee CEN/TC 156 “Ventilation for buildings” the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by April 2009, and conflicting national standards shall be withdrawn at the
latest by April 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 13350:1999 has been approved by CEN as a EN ISO 13350:2008 without any modification.
3
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SIST EN ISO 13350:2009
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SIST EN ISO 13350:2009
INTERNATIONAL ISO
STANDARD 13350
First edition
1999-10-01
Industrial fans — Performance testing of jet
fans
Ventilateurs industriels — Essai de performance des ventilateurs
accélérateurs
A
Reference number
ISO 13350:1999(E)
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SIST EN ISO 13350:2009
ISO 13350:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 Definitions .2
4 Symbols and abbreviations .4
5 Characteristics to be measured .5
6 Instrumentation and measurements.5
7 Determination of thrust .6
8 Determination of sound level .11
9 Determination of vibration velocity.13
10 Determination of flowrate .15
11 Presentation of results.18
12 Tolerances and conversion rules.19
Annex A (informative) Illustration of reference sound source.21
Annex B (informative) Correction of sound pressure levels.22
Annex C (informative) Conversion rules.23
Annex D (informative) Bibliography .25
© ISO 1999
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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SIST EN ISO 13350:2009
© ISO
ISO 13350:1999(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.
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.
International Standard ISO 13350 was prepared by Technical Committee ISO/TC 117, Industrial fans.
Annexes A, B, C and D of this International Standard are for information only.
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SIST EN ISO 13350:2009
© ISO
ISO 13350:1999(E)
Introduction
The need for this new standard has been evident for some time. The use of the so-called jet fan to assist in
controlling the quality of air in vehicle and train tunnels has become increasingly popular. The longitudinal method of
ventilation can show advantages in initial cost and running cost compared to alternative systems, and smoke control
in emergency conditions can be readily provided. At present, there is no published national or international standard
for the performance testing of jet fans.
This International Standard, which forms part of the ISO/TC 117 series of fan standards, deals with the
determination of those performance criteria essential to the correct application of jet fans. In describing the test and
rating procedures, numerous references are made to ISO 5801 as well as to other relevant International Standards.
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SIST EN ISO 13350:2009
INTERNATIONAL STANDARD © ISO ISO 13350:1999(E)
Industrial fans — Performance testing of jet fans
1 Scope
This International Standard deals with the determination of those technical characteristics needed to describe all
aspects of the performance of jet fans as defined in ISO 13349. It does not cover those fans designed for ducted
applications, nor those designed solely for air circulation, e.g. ceiling fans and table fans.
The test procedures described in this International Standard relate to laboratory conditions. The measurement of
performance under on-site conditions is not included.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Member of IEC and ISO maintain
registers for currently valid International Standards.
ISO 1940-1:1986,
Mechanical vibration — Balance quality requirements of rigid rotors — Part 1: Determination of
permissible residual unbalance.
ISO 5801:1997, Industrial fans — Performance testing using standardized airways.
1)
ISO 13347:— , Industrial fans — Determination of fan sound power level under standardized laboratory
conditions.
1)
ISO 13349:— , Industrial fans — Vocabulary and definitions of categories.
1)
ISO 14695:— , Industrial fans — Vibration measurement method.
IEC 60034-2:1972, Rotating electrical machines — Part 2: Methods for determining losses and efficiency of rotating
electrical machinery from tests (excluding machines for traction vehicules).
IEC 60034-14:1996, Rotating electrical machines — Part 14: Mechanical vibration of certain machines with shaft
heights 56 mm and higher — Measurement, evaluation and limits of the vibration severity.
1)
To be published.
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SIST EN ISO 13350:2009
© ISO
ISO 13350:1999(E)
3 Definitions
For the purposes of this International Standard, the definitions given in ISO 13349, ISO 5801 and the following
apply.
3.1
effective fan dynamic pressure
p
d
conventional quantity representative of the dynamic component of the fan output, calculated, in the particular case
of a jet fan, from the effective fan outlet velocity and the inlet density
NOTE The effective fan dynamic pressure will not be the same as the average of the dynamic pressures across the
section because it excludes from consideration that part of the dynamic energy flux which is due only to departures from
uniform axial velocity distribution.
3.2
effective fan outlet area
A
eff
in the particular case of a jet fan, outlet area with deductions for motors, fairings or other obstructions
NOTE 1 If the silencer centrebody reaches the outlet plane of the fan, then the effective fan outlet area is defined as the
annulus area at the fan outlet plane as shown in figure 1a).
NOTE 2 If the fan has a silencer without centrebody [see figure 1 b)], the effective fan outlet area will be close to the cross-
sectional area inside the silencer in order to clear any exit bellmouth form.
NOTE 3 If the centrebody (motor or silencer core) does not extend to the outlet plane, the effective fan outlet area will
approach the annulus area between the casing and the motor, but with some increase, as defined in figure 1c), for the distance
between the centrebody and the outlet. Where the motor is on the upstream side, figure 1c) is applied to the impeller hub rather
than the motor, as illustrated.
Figure 1 — Effective fan outlet area
3.3
effective fan outlet velocity
v
eff
calculated from the thrust, the inlet density and the effective fan outlet area as detailed in 11.2
3.4
fan outlet velocity
in the particular case of a jet fan, inlet volume flow divided by effective fan outlet area, A
eff
3.5
fan air power
conventional power output; in the particular case of a jet fan, product of inlet volume flow and effective fan dynamic
pressure
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SIST EN ISO 13350:2009
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ISO 13350:1999(E)
3.6
impeller tip speed
u
peripheral speed of the impeller blade tips
3.7
thrust
T , T
m c
fan thrust measured or calculated in accordance with this International Standard
3.8
thrust/power ratio
r
t
thrust divided by impeller power
NOTE An alternative definition of thrust/power ratio which has sometimes been used: thrust divided by motor input power.
This definition is deprecated, as it will vary according to the motor manufacturer used. It also results in a lower value, as the
motor losses are included.
3.9
fan guard
guard designed to prevent the ingestion of relatively large foreign bodies, such as drink cans, and sometimes fitted
to the inlet and outlet of jet fans
NOTE Guards can have a marked effect on the thrust performance and noise level. Where they are specified,
measurements should be made with these guards in place.
3.10
chamber
airway in which the air velocity is small compared with that at the fan inlet or outlet
3.11
test enclosure
room, or other space protected from draught, in which the fan and test airways are situated
3.12
impeller balance grade
grade G as specified in ISO 1940-1
3.13
fan vibration velocity
unfiltered r.m.s. vibration velocity over the frequency range 10 Hz to 10 kHz measured in accordance with this
International Standard and with ISO 14695
3.14
fan impeller efficiency
h
R
fan air power divided by impeller power
3.15
overall efficiency
h
E
fan air power divided by motor input power
3.16
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the sound pressure radiated by the sound source
under test to the square of the reference sound pressure
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ISO 13350:1999(E)
3.17
sound power level
L
w
ten times the logarithm to the base 10 of the ratio of the sound power radiated by the sound source under test to the
reference sound power
3.18
inlet sound power level
L
w1
sound power level of the fan determined at the fan inlet
3.19
outlet sound power level
L
w2
sound power level of the fan determined at the fan outlet
3.20
frequency range of interest
for general purposes, the frequency range including the octave bands with centre frequencies between 63 Hz and
8 000 Hz and the one-third octave bands with centre frequencies between 50 Hz and 10 000 Hz
4 Symbols and abbreviations
The following symbols and units shall apply for the parameters listed.
Parameter Symbol Unit
2
Effective fan outlet area A
m
eff
Nominal fan diameter D m
R
Length of upstream chamber side D m
3
Sound pressure level L
p dB (ref. 20 Pa)m
Sound power level L dB (ref. 1 pW)
w
Inlet sound power level L dB (ref. 1 pW)
w1
Outlet sound power level L dB (ref. 1 pW)
w2
rotational speed N r/s
Differential pressure across a flow measuring device p P
a
Effective fan dynamic pressure p P
d a
3
Volume flow q
m /s
V
Impeller balance grade (ISO 1940-1) Gmm
Thrust/power ratio r N/kW
t
Calculated thrust T N
c
Measured thrust T N
m
Impeller tip speed (see 3.6) u m/s
Effective fan outlet velocity v m/s
eff
Mean throughflow velocity in a tunnel at a specified section v m/s
t
3
Inlet density taken as equal to the density in the test enclosurerkg/m
a
Overall efficiency —hE
Motor efficiency —hM
Fan impeller efficiency —hR
4
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SIST EN ISO 13350:2009
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ISO 13350:1999(E)
5 Characteristics to be measured
5.1 General
In order that a jet type fan be correctly applied and give satisfactory performance and reliability in service, it is
necessary to determine a number of technical performance characteristics in addition to knowing the more obvious
mechanical features such as mass, overall dimensions and installation dimensions.
5.2 Thrust
Friction on the tunnel walls, inlet and outlet losses and sometimes traffic drag, combined with climatic effects at
tunnel portals, create a pressure drop through the tunnel. The pressure drop is matched by the sum of the pressure
increases by the jet fans due to the momentum transfer between fan discharge airflow and airflow in the tunnel. As it
is impossible to measure the momentum of the fan discharge airflow, and the rate of change in momentum is equal
and opposite to the thrust, thrust is measured instead.
5.3 Input power
In order to calculate the cost of operating the jet fans in a tunnel, and there may be a substantial number, it is
necessary to know the input power to the fan motor.
5.4 Sound levels
Sound levels, usually at inlet and outlet, are established in order to ensure that the jet fan and silencer combination
is optimized to match the tunnel sound level requirements.
NOTE The fan manufacturer can only guarantee the sound power level of the fan. The sound pressure in the tunnel will
depend on the size and sound absorption characteristics of the tunnel, which are outside the fan manufacturer's responsibility.
5.5 Vibration velocity
For reasons of safety, reliability and maintainability, it is essential that a realistic vibration velocity is specified and
recorded on tunnel fans. These shall be measured at the support points in accordance with ISO 14695.
5.6 Volume flowrate
Volume flowrate need only be measured if required for contractual reasons. It is the effective fan outlet velocity
which is used to evaluate the optimum number, size and spacing of jet fans in a tunnel, and is calculated in
accordance with 11.2.
6 Instrumentation and measurements
6.1 Dimensions and areas
The measurement of dimensions and the determination of areas shall be in accordance with clause 10 of ISO
5801:1997.
6.2 Rotational speed
The rotational speed of the impeller shall be determined in accordance with clause 8 of ISO 5801:1997.
6.3 Thrust
6.3.1 Force balance systems
By the use of calibrated weights, force balance systems shall permit the determination of force or thrust with an
uncertainty of ± 5 %.
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SIST EN ISO 13350:2009
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ISO 13350:1999(E)
6.3.2 Force transducers
After calibration by the use of calibrated weights, force transducers shall permit the determination of thrust with an
uncertainty of ± 5 %.
6.4 Input power
Determination of the power input to the electric motor or to the impeller shall be carried out in accordance with
clause 9 of ISO 5801:1997.
6.5 Sound level
The sound-level measuring system, including microphones, windshields, cables, amplifiers and frequency analyser,
shall be in accordance with the requirements given in ISO 13347.
6.6 Vibration velocity
Instruments to measure r.m.s. vibration velocity shall be used to record fan vibration velocities. These shall be in
accordance with ISO 14695.
6.7 Volume flowrate
6.7.1 Instruments for the measurement of pressure.
Manometers for the measurement of differential pressure, and barometers for the measurement of atmospheric
pressure in the test enclosure, shall comply with the requirements of clause 5 of ISO 5801:1997.
6.7.2 Instruments for the measurement of temperature.
Thermometers shall comply with the requirements of clause 7 of ISO 5801:1997.
7 Determination of thrust
7.1 General
There are two basic configurations acceptable for the determination of fan thrust: suspended configuration and
supported configuration. In addition to the need to measure force accurately, the first method requires that the
suspension elements be kept precisely vertical and parallel with a vertical plane(s) passing through the fan axis,
whilst the second method requires accurate construction and levelling of the support assembly. In either case,
thrust shall be determined by the use of calibrated weights, spring balance or force transducer.
7.2 Suspended configuration
Figures 2 and 3 show typical arrangements of suspended configurations. The fan is suspended from a framework or
gantry with the suspension elements at least one fan-diameter long. The frame should allow free airflow, particularly
at the fan inlet. Below or surrounding the fan is a rigid framework which serves a threefold function:
a) provide the reference point for the fan test assembly under static conditions,
b) provide support for a pulley system to take calibrated weights or a spring balance, and
c) provide a reaction point for a force transducer.
Under operating conditions, the measuring system loads are adjusted to return the fan to the static positions, to
within ± 2 mm, and thus ensure that the suspension elements are precisely vertical. The thrust can then be
measured directly.
NOTE It should be noted that with the thrust/weight ratios typical a of jet fan, it is doubtful whether the desired accuracy of
thrust measurement can be attained by other means, such as measuring the angle of the suspension elements from the
vertical or the change in height between the fan switched off and operational, and then calculating the thrust.
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SIST EN ISO 13350:2009
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Key
1 Adjustable position of transducer/measuring system
2 Air flow
NOTE The fan should be accurately levelled prior to testing.
Figure 2 — Thrust measuring layout (suspended method 1)
Key
4 Adjustable restraint
1 Suspension cables
5 Reference point
2 Air flow
3 Spring balance
NOTE The fan should be accurately levelled prior to testing.
Figure 3 — Thrust measuring layout (suspended method 2)
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SIST EN ISO 13350:2009
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ISO 13350:1999(E)
7.3 Supported configuration
Arrangements of the supported configuration are shown in figures 4, 5 and 6. The fan is supported, via low-friction
linear bearings or leaf springs, on a rigid framework. The fan, to an extent limited by stops, is free to move in either
direction. Before commencing any tests, the assembly shall be carefully levelled, in each direction, such that the
same effort is required to move the assembly along the axis of the fan in either direction.
Under operating conditions, the measuring system loads are adjusted to ensure the movement is not being
restrained by the stops. Thrust can then be measured directly. In the case of the use of a force transducer, the fan
can be allowed to abut the sensor directly.
Key
4 Fan movement possible
1 Direction of fan movement
5 Thrust gauge (measurement in kg direct off gauge + mass of gauge in
2 Air flow
suspension = thrust)
3 Linear bearings
NOTE The fan should be accurately levelled prior to testing.
Figure 4 — Thrust measuring layout (supported method 1)
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SIST EN ISO 13350:2009
© ISO
ISO 13350:1999(E)
Key
4 Linear bearings
1 Direction of fan movement
5 Fan movement possible
2 Air flow
3 Transducer/measuring system
NOTE The fan should be accurately levelled prior to testing.
Figure 5 — Thrust measuring layout (supported method 2)
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SIST EN ISO 13350:2009
© ISO
ISO 13350:1999(E)
Key
3 Leaf spring
1 Direction of fan movement
4 Load cell
2 Air flow
NOTE The fan should be accurately levelled prior to testing.
Figure 6 — Thrust measuring layout (supported method 3)
7.4 Test procedures
To ensure that thrust is measured to the required accuracy, steps shall be taken to minimize errors due to setting-
up/rigging of the test arrangement. Though calibrated weights or spring balances are specified, if a spring balance is
employed to register thrust and it is supported via a pulley, its mass must be accurately known and added to the
measured thrust.
If a force transducer is being used to measure thrust, it is recommended that it is calibrated, for example by using a
pulley and weight system, at no more than 12-monthly intervals. Where the deviation is more than 1 % of the
reading, then recalibration shall be reduced to 3-monthly intervals.
Where the supported method is being used, precautions shall be taken to ensure that the force required to move the
fan in either direction is the same and that the assembly is therefore level.
Thrust readings shall be recorded when both the thrust and power input readings have stabilized, or at least 10 min
after start-up.
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SIST EN ISO 13350:2009
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ISO 13350:1999(E)
7.5 Test enclosure
Figure 7 shows the clearances required in the test enclosure.
Dimensions in meters
Key
1 Plane through impeller
2 Air flow
Figure 7 — Thrust measuring enclosure
8 Determination of sound level
8.1 General
Sound levels are measured by the semireverberant method. The method is essentially practical and, apart from the
sound-measuring instrumentation, minimal facilities are required: a suitable enclosure and a calibrated sound
source.
As the fan has only one operating point, at zero resistance, there are no complications which could arise from the
noise generated by the “loading means”. Similarly, since only open inlet or open outlet sound levels are required,
anechoic terminators are unnecessary. It should be recognized that the method measures the noise radiated by the
fan, whether from the fan inlet or outlet or from the fan casing, thus representing the same situation as when the fan
is installed in a tunnel.
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SIST EN ISO 13350:2009
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ISO 13350:1999(E)
8.2 Test arrangement
Positioning of the fan, calibrated reference sound source and the microphone paths are shown in figure 8.
Key
3 Primary microphone path
1 Reference source
4 All surfaces hard finish
2 Secondary microphone path
NOTE
1 Microphone traverse plane should be greater than 10° from parallel to any surface.
2 Maximum air velocity over microphone 1 m/s.
3 Microphone, RSS, fan sound sources cannot be within 0,3 m of room centrelines.
4 Equipment or vane placement is not restricted by this International Standard provided above conditions are met.
5 Room shape is not specified in this International Standard, but rooms having certain proportions will perform more
successfully (6).
6 Room volume is not specified, but the room should be large enough in volume such that the volume of the test fan and
associated duct work does not exceed 1 % of that room volume.
Figure 8 — Semi-reverberant enclosure
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ISO 13350:1999(E)
8.3 Enclosure suitability
The semireverberant chamber shall meet the requirements of ISO 13347.
A primary microphone path shall be located on an arc or straight line of length between 1,5 m and 3 m at a distance
of not less than 2 m from any major reflecting surface. No point on this path shall be within 45° of the centreline of
the fan sound source, and the path itself shall form an angle greater than 10° with any chamber surface and shall be
located towards a corner of the chamber. The path shall be so located that the microphone is not subjected to an air
velocity in excess of 2 m/s (see figure 8).
A reference sound source shall be located such that its acoustic centre is the same distance from the midpoint of
the microphone path as the centre of the fan sound, but not nearer than 1 m to the latter, or to any major reflecting
surface. The reference sound source shall meet the requirements of ISO 13347. The reference sound source shall
be run at a speed within 2 % of the speed at which it was calibrated.
With the reference sound source operating, but with the test fan impeller stationary, readings of sound pressure
level shall be made in each octave band along the primary microphone path, and the average value along the path
estimated. A secondary microphone path, similar to the primary microphone path and of the same length, shall be
established at a position halfway between the reference sound source an
...
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