SIST EN 60534-8-4:2007
(Main)Industrial-process control valves -- Part 8-4: Noise considerations - Prediction of noise generated by hydrodynamic flow
Industrial-process control valves -- Part 8-4: Noise considerations - Prediction of noise generated by hydrodynamic flow
This part of IEC 60534 establishes a method to predict the noise generated in a control valve by liquid flow and the resulting noise level measured downstream of the valve and outside of the pipe. The noise may be generated both by normal turbulence and by liquid cavitation in the valve. Parts of the method are based on fundamental principles of acoustics, fluid mechanics, and mechanics. The method is validated by test data. Noise generated by flashing flow is not considered in this standard. The transmission loss (TL) equations are based on analysis of the interaction between the sound waves inside the pipe and the coincidence frequencies in the wall of the pipe taking into account that commercial pipe tolerances allow a relatively wide variation in the thickness of the pipe wall. Ideal straight piping is assumed. The method can be used with all conventional control valve styles including globe, butterfly, cage-type, eccentric rotary, and modified ball valves. Tests so far have only been conducted with water. The applicability of this method for fluids other than water is not known at this time. This standard considers only noise generated by hydraulic turbulence and fluid cavitation. It does not consider any noise that might be generated by mechanical vibrations, unstable flow patterns, and unpredictable behaviour. In the typical installation, very little noise travels through the wall of the control valve body. The noise is measured at the standard measuring point of 1 m downstream of the valve and 1 m away from the outer surface of the pipe. This prediction method has been validated with test results based on water covering more than 90 % of all known valve types at inlet pressures of up to 15 bar. This method is considered accurate within ± 5dB(A) except in the range of xF = xFz ± 0,1, when xFz is calculated using equations (3a) or (3b).
Stellventile für die Prozessregelung -- Teil 8-4: Geräuschbetrachtungen - Vorausberechnung der Geräuschemission für flüssigkeitsdurchströmte Stellventile
Vannes de régulation des processus industriels -- Partie 8-4: Considérations sur le bruit - Prévision du bruit généré par un écoulement hydrodynamique
Etablit une méthode pour prévoir le bruit engendré dans une vanne de régulation par un écoulement liquide et le niveau de bruit mesuré en aval de la vanne et à l'extérieur de la tuyauterie. Le bruit peut être généré à la fois par des turbulences normales et par la cavitation du liquide dans la vanne.
Regulacijski ventili za industrijske procese - 8-4. del: Šum - Predvidevanje šuma, ki ga proizvaja hidrodinamični pretok (IEC 60534-8-4:2005)
General Information
Relations
Standards Content (Sample)
SLOVENSKI SIST EN 60534-8-4:2007
STANDARD
januar 2007
Regulacijski ventili za industrijske procese - 8-4. del: Šum - Predvidevanje
šuma, ki ga proizvaja hidrodinamični pretok (IEC 60534-8-4:2005)
(istoveten EN 60534-8-4:2005)
Industrial-process control valves - Part 8-4: Noise considerations - Prediction of
noise generated by hydrodynamic flow (IEC 60534-8-4:2005)
ICS 17.140.20; 23.060.40; 25.040.40 Referenčna številka
SIST EN 60534-8-4:2007(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 60534-8-4
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2005
ICS 23.060.40; 17.140.20; 25.040.40 Supersedes EN 60534-8-4:1994
English version
Industrial-process control valves
Part 8-4: Noise considerations -
Prediction of noise generated by hydrodynamic flow
(IEC 60534-8-4:2005)
Vannes de régulation Stellventile für die Prozessregelung
des processus industriels Teil 8-4: Geräuschbetrachtungen -
Partie 8-4: Considérations sur le bruit - Vorausberechnung der Geräuschemission
Prévision du bruit généré für flüssigkeitsdurchströmte Stellventile
par un écoulement hydrodynamique (IEC 60534-8-4:2005)
(CEI 60534-8-4:2005)
This European Standard was approved by CENELEC on 2005-11-01. CENELEC 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 Central Secretariat or to any CENELEC 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 CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60534-8-4:2005 E
---------------------- Page: 2 ----------------------
EN 60534-8-4:2005 - 2 -
Foreword
The text of document 65B/556/FDIS, future edition 2 of IEC 60534-8-4, prepared by SC 65B, Devices,
of IEC TC 65, Industrial-process measurement and control, was submitted to the IEC-CENELEC
parallel vote and was approved by CENELEC as EN 60534-8-4 on 2005-11-01.
This European Standard supersedes EN 60534-8-4:1994.
The noise prediction methods for hydrodynamic flow presented in this standard have been revised.
The improvements are mainly in the acoustic efficiency factors for cavitating flow for single orifice,
multi-stage and multi-hole trims and in the determination of transmission losses. This revised standard
permits the prediction of the noise pressure levels by calculation without the need for coefficients
determined by testing.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-11-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60534-8-4:2005 was approved by CENELEC as a
European Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60534-8-4:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application 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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60534-1 - Industrial-process control valves EN 60534-1 2005
Part 1: Control valve terminology and
general considerations
1) 2)
IEC 60534-8-2 - Part 8: Noise considerations EN 60534-8-2 1993
Section 2: Laboratory measurement of
noise generated by hydrodynamic flow
through control valves
1) 2)
IEC 60534-8-3 - Part 8-3: Noise considerations - Control EN 60534-8-3 2000
valve aerodynamic noise prediction
method
1)
Undated reference.
2)
Valid edition at date of issue.
---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE
IEC
60534-8-4
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2005-08
Vannes de régulation des processus
industriels –
Partie 8-4:
Considérations sur le bruit –
Prévision du bruit généré par
un écoulement hydrodynamique
Industrial-process control valves –
Part 8-4:
Noise considerations –
Prediction of noise generated
by hydrodynamic flow
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électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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Commission Electrotechnique Internationale
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МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 5 ----------------------
60534-8-4 ” IEC:2005 – 3 –
CONTENTS
FOREWORD.5
INTRODUCTION . 11
1 Scope. 13
2 Normative references. 13
3 Symbols . 15
4 Preliminary calculations . 19
4.1 Pressures and pressure ratios. 19
4.2 Characteristic presssure ratio x . 19
Fz
4.3 Valve style modifier F . 21
d
4.4 Jet diameter D . 21
j
4.5 Jet velocity . 21
4.6 Mechanical power W . 21
m
5 Noise predictions. 23
5.1 Internal noise. 23
5.2 Transmission loss . 25
5.3 External noise. 27
5.4 Frequency distribution (internal and external). 27
6 Multistage trim. 29
6.1 General. 29
6.2 Preliminary calculations . 29
6.3 Prediction of noise level. 31
Annex A (informative) Examples . 45
Bibliography. 55
Figure 1 – Examples of multistage trim in globe and rotary valves . 33
Figure 2 – Example of fixed multistage device with increasing flow area. 35
Figure 3 – Example of multistage trim in globe valve . 37
Figure 4 – Globe valves (cage trim. V-port-plug). 39
Figure 5 – Globe valves (parabolic-plug). 39
Figure 6 – Multihole trims. 41
Figure 7 – Eccentric rotary valves . 41
Figure 8 – Butterfly valves. 43
Figure 9 – Segmented ball valve – 90° travel. 43
Figure A.1 – Influence of x value on prediction accuracy. 53
Fz
Table 1 – Numerical constants N. 21
Table 2 – Acoustic power ratio r . 21
W
Table A.1 – Calculation examples . 47
---------------------- Page: 6 ----------------------
60534-8-4 IEC:2005 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL-PROCESS CONTROL VALVES –
Part 8-4: Noise considerations –
Prediction of noise generated by hydrodynamic flow
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60534-8-4 has been prepared by subcommittee 65B: Devices, of
IEC technical committee 65: Industrial-process measurement and control.
This second edition cancels and replaces the first edition published in 1994. This edition
constitutes a technical revision.
The noise prediction methods for hydrodynamic flow presented in this standard have been
revised. The improvements are mainly in the acoustic efficiency factors for cavitating flow for
single orifice, multi-stage and multi-hole trims and in the determination of transmission losses.
This revised standard permits the prediction of the noise pressure levels by calculation
without the need for coefficients determined by testing. This method is considered accurate
= x ± 0,1 when x is calculated using equations
within ± 5 dB(A) except in the range of x
F Fz Fz
3(a) or (3b) for estimation. More accurate results are possible when x is determined from
Fz
measurements according to IEC 60534-8-2.
---------------------- Page: 7 ----------------------
60534-8-4 ” IEC:2005 – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
65B/556/FDIS 65B/560/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 60534 comprises the following parts, under the general title Industrial – process control
valves:
Part 1: Control valve terminology and general considerations
Part 2-1: Flow capacity – Sizing equations for fluid flow under installed conditions
Part 2-3: Flow capacity – Test procedures
Part 2-4: Part 2: Flow capacity – Inherent flow characteristics and rangeability
Part 2-5: Flow capacity – Sizing equations for fluid flow through multistage control valves
with interstage recovery
Part 3-1: Dimensions – Face-to-face dimensions for flanged, two-way, globe-type,
straight pattern and centre-to-face dimensions for flanged, two-way, globe-
type, angle pattern control valves
Part 3-2: Dimensions – Face-to-face dimensions for rotary control valves except butterfly
valves
Part 3-3: Dimensions – End-to-end dimensions for buttweld, two-way, globe-type,
straight pattern control valves
Part 4: Inspection and routine testing
Part 5: Marking
Part 6-1: Mounting details for attachment of positioners to control valves – Positioner
mounting on linear actuators
Part 6-2: Mounting details for attachment of positioners to control valves – Positioner
mounting on rotary actuators
Part 7: Valve data sheet
Part 8-1: Noise considerations – Laboratory measurement of noise generated by aero-
dynamic flow through control valves
Part 8-2: Noise considerations – Laboratory measurement of noise generated by hydro-
dynamic flow through control valves
Part 8-3: Noise considerations – Control valve aerodynamic noise prediction method
Part 8-4: Noise considerations – Prediction of noise generated by hydrodynamic flow
Part 9: Test procedure for response measurements from step inputs
---------------------- Page: 8 ----------------------
60534-8-4 IEC:2005 – 9 –
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of February 2006 have been included in this copy.
---------------------- Page: 9 ----------------------
60534-8-4 ” IEC:2005 – 11 –
INTRODUCTION
It is valuable to predict the noise levels that will be generated by valves. Safety requirements,
such as occupational health standards, require that human exposure to noise be limited.
There is also data indicating that noise levels above certain levels could lead to pipe failure or
affect associated equipment (see IEC 60534-8-3). Earlier hydrodynamic noise standards
relied on manufacturer test data and were neither generic nor as complete as desired.
A valve restricts flow by converting pressure energy into turbulence, heat and mechanical
pressure waves in the containing valve body and piping. A small portion of this mechanical
vibration is converted into acoustical energy. Most of the noise is retained within the piping
system with only a small portion passing through the pipe wall downstream of the valve.
Calculation of the energy involved is straightforward. The difficulties arise from determining
first the acoustic efficiency of the mechanical energy to noise conversion and then the noise
attenuation caused by the pipe wall.
---------------------- Page: 10 ----------------------
60534-8-4 IEC:2005 – 13 –
INDUSTRIAL-PROCESS CONTROL VALVES –
Part 8-4: Noise considerations –
Prediction of noise generated by hydrodynamic flow
1 Scope
This part of IEC 60534 establishes a method to predict the noise generated in a control valve
by liquid flow and the resulting noise level measured downstream of the valve and outside of
the pipe. The noise may be generated both by normal turbulence and by liquid cavitation in
the valve. Parts of the method are based on fundamental principles of acoustics, fluid
mechanics, and mechanics. The method is validated by test data. Noise generated by flashing
flow is not considered in this standard.
The transmission loss (TL) equations are based on analysis of the interaction between the
sound waves inside the pipe and the coincidence frequencies in the wall of the pipe taking
into account that commercial pipe tolerances allow a relatively wide variation in the thickness
of the pipe wall. Ideal straight piping is assumed.
The method can be used with all conventional control valve styles including globe, butterfly,
cage-type, eccentric rotary, and modified ball valves. Tests so far have only been conducted
with water. The applicability of this method for fluids other than water is not known at this
time.
This standard considers only noise generated by hydraulic turbulence and fluid cavitation. It
does not consider any noise that might be generated by mechanical vibrations, unstable flow
patterns, and unpredictable behaviour. In the typical installation, very little noise travels
through the wall of the control valve body. The noise is measured at the standard measuring
point of 1 m downstream of the valve and 1 m away from the outer surface of the pipe.
This prediction method has been validated with test results based on water covering more
than 90 % of all known valve types at inlet pressures of up to 15 bar. This method is
considered accurate within ± 5dB(A) except in the range of x = x ± 0,1, when x is
F Fz Fz
calculated using equations (3a) or (3b).
2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60534-1, Industrial-process control valves – Part 1: Control valve terminology and
general considerations
IEC 60534-8-2, Industrial-process control valves – Part 8: Noise considerations – Section 2:
Laboratory measurement of noise generated by hydrodynamic flow through control valves
---------------------- Page: 11 ----------------------
60534-8-4 IEC:2005 – 15 –
IEC 60534-8-3, Industrial-process control valves – Part 8-3: Noise considerations – Control
valve aerodynamic noise prediction method
3 Symbols
Symbol Description Unit
A(f) Frequency-dependent A-weighting value dBA (ref P )
o
c Speed of sound in liquid m/s
L
c Speed of sound in air = 343 m/s
o
c Speed of sound in pipe (for steel pipe 5 000) m/s
p
C Flow coefficient (K and C ) Various (see
v v
IEC 60534-1)
C Flow coefficient (K and C ) at rated travel Various (see
R v v
IEC 60534-1)
C Flow coefficent of first stage in a multistage valve (K and C ) Various (see
1 v v
IEC 60534-1)
C Flow coefficent of last stage in a multistage valve (K and C ) Various (see
n v v
IEC 60534-1)
D Internal pipe diameter m
i
D
Jet diameter m
j
d Valve inlet internal diameter m
d Multihole trim hole diameter m
H
d Seat or orifice diameter m
o
F Frequency distribution function (cavitating) Dimensionless
cav
F Valve style modifier Dimensionless
d
F
Liquid pressure recovery factor of a valve without attached Dimensionless
L
fittings
F
Liquid pressure recovery factor of the last throttling stage Dimensionless
Ln
F Frequency distribution function (turbulent) Dimensionless
turb
f Frequency Hz
f Octave band frequency Hz
ji
f Ring frequency Hz
r
f Internal peak sound frequency (turbulent) Hz
p,turb
f
Internal peak sound frequency (cavitating) Hz
p,cav
L Overall external sound pressure level 1 m from pipe wall dB (ref P )
pe,1m o
L A-weighted overall external sound pressure level 1 m from dBA (ref P )
pAe,1m o
pipe wall
L A-weighted external sound pressure level 1 m from pipe wall dBA (ref P )
pAe,1m,i o
of stage i (number i from 1…n) in multistage valve with n
stages
L Overall internal sound pressure level at pipe wall dB (ref P )
pi o
L (f ) dB (ref P )
Frequency-dependent internal sound pressure level
pi i o
Mass flow rate kg/s
&
m
---------------------- Page: 12 ----------------------
60534-8-4 IEC:2005 – 17 –
n Number of stages in multistage trim Dimensionless
N Numerical constants (see Table 1) Various
N Number of independent and identical flow passages in valve Dimensionless
o
trim or throttling stage
N Strouhal number of jet Dimensionless
STR
5
P Pa
Reference pressure = 1 × 10
a
-5
P Pa
Reference sound pressure = 2 × 10
o
p Valve inlet absolute pressure Pa
1
p Valve outlet absolute pressure Pa
2
p Inlet absolute pressure of stage i (number i from 1…n) in Pa
1,i
multistage valve with n stages
p Outlet absolute pressure of stage i (number i from 1…n) in Pa
2,i
multistage valve with n stages
p
Vapour pressure of liquid Pa
v
Δp Pressure differential Pa
Pressure differential for U calculation Pa
Δp
vc
c
r
Acoustic power ratio Dimensionless
W
t Pipe-wall thickness m
p
TL Transmission loss dB
TL Overall transmission loss at cavitating conditions dB
cav
Transmission loss corrected for frequency f dB
ΔTL
p,turb
fp,turb
TL Overall transmission loss at turbulent conditions dB
turb
TL Transmission loss at ring frequency f dB
fr r
U
Vena contracta velocity m/s
vc
W Sound power W
a
W Mechanical stream power W
m
x Differential pressure ratio Dimensionless
F
x Differential pressure ratio of incipient cavitation noise with Dimensionless
Fz
5
inlet pressure of 6 × 10 Pa
x Differential pressure ratio corrected for inlet pressure Dimensionless
Fzp1
Acoustic efficiency factor (turbulent) Dimensionless
η
turb
Acoustic efficiency factor (cavitating) Dimensionless
η
cav
3
Density kg/m
ρ
3
Density of air = 1,293 kg/m
ρ
o
3
Density of pipe material (= 7 800 for steel) kg/m
ρ
p
3
Density of liquid kg/m
ρ
L
cav Cavitation
turb Turbulent
i Pipe internal or counter index
p Pipe
Vena contracta
vc
---------------------- Page: 13 ----------------------
60534-8-4 ” IEC:2005 – 19 –
4 Preliminary calculations
4.1 Pressures and pressure ratios
Several pressures and pressure ratios which are needed in the noise prediction procedure are
given below.
The differential pressure ratio x for liquids depends on the pressure difference p -p and the
F 1 2
difference of the inlet pressure p and the vapour pressure p .
1 v
p p
1 2
x (1)
F
p p
1 v
2
The differential pressure for beginning a choked flow is approximately F (p –p ). Some
L 1 v
calculations are based on the following pressure differential:
2
'p lower than p p or FL p p (2)
c 1 2 1 v
For low differential pressure ratios, the noise is mainly generated by turbulence. If x exceeds
F
x cavitation noise overlays the turbulent noise.
Fz,p1
4.2 Characteristic presssure ratio x
Fz
The valve-specific characteristic pressure ratio x can be measured with dependency on the
Fz
valve travel according to IEC 60534-8-2. It identifies the pressure ratio at which cavitation is
acoustically detected. The value of x depends on the valve and closure member type and
Fz
the specific flow capacity.
Alternatively, the value of x can be estimated from equations (3a) and (3b). Calculations of
Fz
hydrodynamic noise based on equations (3a), (3b) and (3c) can create uncertainties as
illustrated in Annex A. Figures 4 to 9 include typical curves of x for different control valve
Fz
5
types. Both equation (3a) and Figures 4 to 9 are based on an inlet pressure of 6 u 10 Pa. If a
different inlet pressure is required, then the x value shall be corrected using equation (3c).
Fz
0,90
XFz for valve types except multihole trims (3a)
C
1 3 F
d
N34˜F
L
1
(3b)
XFz for multihole trims
2
N 0 ˜d
H
4,5 1 650˜
F
L
NOTE N is a numerical constant, the values of which account for the specific flow coefficient (K or C ) used.
34 v v
5
When x is obtained by testing at an inlet pressure of 6 u 10 Pa, then the tested value must
Fz
be corrected for the actual inlet pressure using the following equation:
0,125
5
§ ·
6u 10
¨ ¸
x x (3c)
Fzp1 Fz
¨ ¸
p
1
© ¹
---------------------- Page: 14 ----------------------
60534-8-4 ” IEC:2005 – 21 –
4.3 Valve style modifier F
d
The valve style modifier depends on the valve and closure member type and on the flow
coefficient C (see IEC 60534-8-3).
4.4 Jet diameter D
j
The jet diameter D can be predicted as in IEC 60534-8-3 by the following equation:
j
D N F C F (4)
j 14 d L
4.5 Jet velocity
The vena contracta flow velocity, used in calculating the mechanical power, is determined as
follows:
1 2 'p
c
U (5)
vc
F U
L L
4.6 Mechanical power W
m
The mechanical energy dissipated in the valve orifice is determined from the following
equation:
2 2
mU F
vc L
W (6)
m
2
Table 1 – Numerical constants N
Flow coefficent
K C
Constant
v v
-3 -3
N
4,9 u 10 4,6 u 10
14
N 1 1,17
34
Table 2 – Acoustic power ratio r
W
r
Valve or fitting
W
Globe, parabolic plug 0,25
Globe, 3 V port plug 0,25
Globe, 4 V port plug 0,25
Globe, 6 V port plug 0,25
Globe, 60 equal diameter hole drilled cage 0,25
Globe, 120 equal diameter hole drilled cage 0,25
Butterfly, swing-through (centred shaft), to 70º 0,5
Butterfly, fluted vane, to 70º 0,5
Butterfly, 60º flat disk 0,5
Eccentric rotary plug 0,25
Segmented ball 90º 0,25
Expanders 1
---------------------- Page: 15 ----------------------
60534-8-4 ” IEC:2005 – 23 –
5 Noise predictions
5.1 Internal noise
The portion of the mechanical power W from 4.6 converted to valve internal noise is a
m
function of the acoustic efficiency K. The acoustic power ratio r represents the fraction of
W
sound power radiated into the pipe. See Table 2 for r values.
W
For turbulent conditions defined here where 'p is lower than x (p – p ):
Fzp1 1 v
W K W r (7a)
a turb m W
For cavitating conditions defined here where 'p exceeds x (p – p ) and x is not greater
Fzp1 1 v F
than 1:
W K K W r (7b)
a turb cav m W
For turbulent flow due to the relatively low fluid velocity U the valve is considered to be a
vc
-4
)
1
monopole source with an acoustical efficiency of approximately 10 at U = c (see [1] ). The
vc L
acoustic efficiency factor for turbulent flow is calculated as follows:
§U ·
4 vc
¨ ¸
K 10 (8)
turb
...
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