ISO/TR 9464:1998

ISOITR
TECHNICAL
9464
REPORT
First edition
1998-05-01
Guidelines for the use of IS0 5167-l :I991
Guide pour I’emploi de IWO 5 I67- I: I99 I
Reference number
ISO/TR 9464:1998(E)

---------------------- Page: 1 ----------------------
ISO/rR 9464: 1998(E)
Page
Contents
Section 1 - Guidelines relating to specific clauses in IS0 5167-l :1991
1 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.*.
4 . . . . . . . .~.~. 2
Symbols and subscripts
3
5 Principle of measurement and computation: Examples . . . . . . . . . . . .
6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
General requirements for measurements
8
7 Installation requirements .,.*.*.
8 Orifices plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
32
9 Nozzles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 Venturi tubes . . . . . . . . . . . . . . . . . . . . . . . .*. 32
36
11 Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Section 2 - Information of a general nature, relevant to the application
of IS0 5167-1
12 Secondary instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
12.1 Introduction
12.2 Measurement of pressure and differential pressure . . . . . . . . 38
12.3 Measurement of temperature (see [ISO 5167-1, 3.4.21
and Code of Practice 3.4.2.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Determination of density (see [ISO 5167-l , 5.41) . . . . . . . . . . . . . 48
12.4
12.5 Electrical supply and electrical installations . . . . . . . . . . . . . . . . . . . . . 54
12.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Annex A Principles of measurement and computation . . . . . . . . . . . . . . . . 55
Annex B References for physical data . . . . . . . . . . . . . . . . . . . . . .e. 71
73
Annex C Computation of compressibility factor for natural gases .
0 IS0 1998
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 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii

---------------------- Page: 2 ----------------------
ISO/rR 9464:1998(E)
@ IS0
FO reword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International
Standards, but in exceptional circumstances a technical committee may
propose the publication of a Technical Report of one of the following types:
when the required support cannot be obtained for the
- type 13
publication of an International Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility of
an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International Standard
(“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years
of publication, to decide whether they can be transformed into International
Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or
useful.
ISO/TR 9464, which is a Technical Report of type 3, was prepared by
Technical Committee lSO/TC 30, Measurement of fluid flow in closed
conduits, Subcommittee SC 2, Differential pressure methods.

---------------------- Page: 3 ----------------------
This page intentionally left blank

---------------------- Page: 4 ----------------------
ISO/rR 9464:1998(E)
TECHNICAL REPORT o Is0
Guidelines for the use of IS0 5167-1:1991
Section 1 - Guidance relating to specific clauses in IS0 5167~I:1991
1 Introduction
The objective of this Technical Report is to assist users of IS0 5167-1:1991. For
convenience of use, it is divided into two Sections, as
Section 1 - Makes reference to specific clauses and subclauses in IS0 5167-1:1991,
and provides guidance on details and interpretation of the requirements specified in
IS0 5167-1:1991. The clause numbers in this Section have been arranged to be the
same as the corresponding clause numbers in IS0 5167-1:1991.
Section 2 - Gives further information of a general nature, relevant to the application of
IS0 5167-1:1991, but does not refer to specific clauses in IS0 5167-1:1991.
In Section 1, cross-reference is simplified by using the same clause and subclause
numbering as in IS0 5167-1. To avoid confusing figures and tables of this Technical
Report with those of the reference standard IS0 5167-1, references to the latter are
made within square brackets, i.e. [.I.
Some clauses of IS0 5167-1 are not commented upon and the corresponding clause
numbers are therefore omitted from this Technical Report, except when it has been
thought to be useful to keep a continuous numbering of paragraphs.
All quantities and constants quoted in this Technical Report are expressed in SI units.
1.1 IS0 5167-l
IS0 5167-I is an International Standard for flow measurement based on the
differential pressure generated by a constriction introduced into a circular conduit
[ISO 5167-1, 5.11. It presents a set of rules and requirements based on theory and
experimental work undertaken in the field of flow measurement. Neither IS0 5167-1
nor this Technical Report give the detailed theoretical background and reference
should be made to any general textbook on fluid flow.
With the application of the rules and requirements set out in IS0 5167-1, it is
practicable to achieve flow measurement within an uncertainty of approximately 1 per
cent on the calculated rate of flow.
For more detailed description of the scope, reference should be made to [ISO 5167-1,
clause I].

---------------------- Page: 5 ----------------------
ISO/TR 9464: 1998(E)
1.2 Selection of the primary device
The constraints applicable to each of the primary devices need to be given proper
consideration before determining the most suitable type for a particular application.
Clause 4 of this Technical Report gives guidance. A final decision should not be made
unless it is clear that, for a particular application, the appropriate requirements of the
clauses and subclauses of IS0 5167-I listed in column 4 of table I of this Technical
Report can be fulfilled.
These paragraphs will also form the basis for preliminary design. [lSO 5167-1,
Clauses 3 and 41 give definitions and symbols.
1.3 Detail design
The information necessary for detailed design, manufacture and final check is specified in
the clauses and paragraphs of IS0 5167-I listed in column 2 of table 1.
1.4 Computation
Operation of a measuring system, once installed, requires several computations to
establish the resultant flow-rate, Some results of these calculations will be fixed with
installation dimensions and will only need to be computed once. Other calculations will
need to be repeated for every flow measurement point. The equations to be used are given
in the clauses and sub-clauses of IS0 5167-l listed in column 3 of table I.
15 . Secondary instrumentation
Secondary instrumentation is not covered by IS0 5167-1 but Section 2 of this
Technical Report makes reference to IS0 2186, which will be required.
2 Normative references
No comments on this clause.
3 Definitions
3.1 Pressure measurement
No comments on this clause
3.2 Primary devices
No comments on this clause
3.3 Flow
No comments on this clause
4 Symbols and subscripts
For explanation of the symbols and definitions, reference is made to [ISO 5167-1,
clause 4.11 which is based on IS0 4006.
2

---------------------- Page: 6 ----------------------
ISCM-R 9464:1998(E)
5
Principle of measurement and computation : Examples
5.1 Principle of the method of measurement
No specific comments on this clause, but note that throughout this guide, p2 and c2 may be
used as alternatives to p1 and q .
5.2 Determination of the diameter ratio
Refer to annex A.
5.3 Determination of the rate of flow
Refer to annex A.
5.4 Determination of the density
For more details on density measurement, see Part 2.
For more details on density computation, see 6*2.
5.4.1 No specific comments on this clause.

---------------------- Page: 7 ----------------------
Table 1 : Reference clauses in IS0 5167-l
1. Selection 3. Computation
2. Desian
3.3, 5.1, 5.3, 11
General 1, 2, 5.1 3.3.6
Fluid and flow conditions 6.2, 6.3 54 . 5.4.3
. 3.2, 6.1.3
Primary device 61
Pipe work 71 . 7.1 and 7.5 or 7.6 7.5.1.2
72 .
Minimum straight lengths 7.2 or 7.4
8.3.2, 8.3.3
Orifice plates 8.3.1, 8.4 8.1, 8.2
9.1.6.1, 9.1.8 9.1.2 to 9.1.5 9.1.6.2, 9.1.6.3, 9.1.7
ISA 1932 nozzles
9.251, 9.2.7 9.2.1 to 9.2.4 9.2.5.2, 9.2.5.3, 9.2.6
Long radius nozzles
10.1.1, 10.1.5, 10.1.9.2
Classical Venturi tubes 10.1.2 to 10.1.4 10.1.5 to 10.1.8
10.2.4.1, 10.2.6 10.2.1 to 10.2.3 10.2.4.2, 10.2.4.3, 10.2.5.1, 10.2.5.2
Venturi nozzles

---------------------- Page: 8 ----------------------
ISO/rR 94643 998(E)
@ IS0
5.4.2 Temperature measurement
Within the limits of application of the international standard [ISO 5167-1, 5.4.21 it may be
assumed that the downstream and the upstream temperatures of the fluid are the same.
For very accurate measurements it is advisable that the actual temperature at the upstream
plane is measured under flowing conditions using a temporarily installed temperature
probe.
If the fluid being measured is a gas and high accuracy is required and there is a large
pressure loss between the upstream pressure tapping and the location of the temperature
measuring device downstream of the primary device, then it is necessary to calculate the
upstream temperature from the temperature measured downstream. Experimental work has
shown that an isenthalpic expansion is a reasonable approximation for orifice plates.
Further work is required to check its correctness for other primary devices. To perform the
calculation, the pressure loss AO should be calculated from IS0 5167-1, 8.4, 9.1.8, 9.2.8,
10.1.9.2, or 10.2.6, The corresponding temperature drop from the upstream tapping to the
downstream temperature measurement location, AT, can be evaluated given the rate of
change of T with respect to p at constant enthalpy:
I
CT
AT=- A0
I
$I,,
RJ-
cz
5
Z------------
- -lo
q,
vcp
where T is the absolute temperature, R, is the universal gas constant, cp is the heat
capacity at constant pressure and Z is the compressibility factor.
In the 1980 edition of IS0 5167-I it was stated that if the measured fluid is a gas an
isentropic expansion should be assumed through the primary device. This is now known to
be incorrect. The complete process includes both isentropic and isenthalpic expansions
between upstream of the primary device and the location at which the static pressure
recovery is completed.
REFERENCE : “Performance Equations for Compressible Flow Through Orifices and Other
LIP Devices : A Thermodynamic Approach”, AlChe Journal, March 1986, Vol. 32, No 3.
5.4.3 No specific comments on this clause.
5.4.4 Temperature of primary device
- -
This assumption is made when correcting the primary device dimensions for temperature
changes when very accurate flow measurement is required.
6 General requirements for measurements
6.1 Material and manufacture
Table 2 whilst not exhaustive, lists materials most commonly used for orifice plate
manufacture.

---------------------- Page: 9 ----------------------
@ IS0
ISOFI-R 94643 998(E)
Table 2 : Commonly used steels for orifice plate manufacture
Stainless steels
stainless steel
I I I I
I I
Table 3 gives the mean linear expansion coefficient, elasticity modulii and yield stresses for
the materials of table 2 according to their AISI designation.
Table 3 : Characteristics of commonly used steels
IO-” Mean Linear
Expansion Coefficient
between 0 and 100°C
NOTE : the figures given in table 3 vary with both temperature and the treatment
process of the steel. For precise calculations it is recommended that the data are
obtained from the manufacturer.
6.1.1 No specific comments on this clause.
6.1.2 No specific comments on this clause.

---------------------- Page: 10 ----------------------
ISO/TR 9464:1998(E)
6.1.3 When the primary device under operating conditions is at a different temperature
from the one at which the diameter “d” was determined (this temperature is referred to as
the reference or calibration temperature) the expansion or contraction of the primary
device shall be taken into account in the computation of diameter ratio and flowrate using
the following equation, assuming there is no restraint due to the mounting :
d = do [I + kd(T - To)]
(1)
where d : primary device diameter in flowing conditions ;
do : primary device diameter at reference temperature ;
hd : mean linear expansion coefficient of the primary device material ;
T : primary device temperature in flowing conditions ;
TO : reference or calibration temperature.
Where automatic temperature correction is not required in the flow computer, the
uncertainty for “d” included in the overall uncertainty calculations should be increased to
allow for the change in “d” due to temperature variation (see IS0 51674, 11.2.2.3). An
initial calculation may show that this additional uncertainty is small enough to be considered
negligible.
6.2
Nature of the fluid
6.2.1 No specific comments on this clause.
6.2.2 Universal gas constant
The value indicated for the universal gas constant
6.2.3 Ascertaining density and viscosity of the flowing fluid
Annex B lists references for physical properties whilst annex C gives specific information for
natural gases. They provide data relating to the dependence of density and viscosity on
. -
temperature and pressure.
For gases, several methods can be used to calculate density from pressure and
temperature :
(a) by using tables, or equations of density versus pressure and temperature.
(b) when the molar mass M of the fluid is known, by first computing the compressibility
factor Zl, in flowing conditions, and then the density using the equation :

---------------------- Page: 11 ----------------------
ISO/rR 9464: 1998(E)
PM
(2)
P1 =
AZ
1 1
where R is the universal gas constant (= 8,314 50 J.mol-l.K-l)
(c) when the density at standard conditions, PR is known (from calculation or
measurement) for given conditions of pressure and temperature, pR and TRY by first
computing the compressibility factors Z1 and ZR and then using the equation :
PAA
P (3)
1=
PRV,
For complex mixtures such as natural gas, the two latter methods are generally the only
practicable ones. Annex C gives a list of the main existing methods of computation of the
compressibility factor Z for a number of gas mixtures.
6.3 Flow conditions
6.3.1 No specific comments on this clause.
6.3.2 If there is a likelihood of such a change of phase, a way of overcoming the problem is
to increase the diameter ratio, so that the differential pressure is reduced.
7 Installation requirements
7.0 Inspection equipment
The following list of inspection equipment is not exhaustive, but provides a basis for
inspection control.
- calipers (thickness, diameters) ;
- internal micrometer (diameters) ;
- micrometer (thickness) ;
- gauge block, feeler gauge (relative position, absolute standard for checking
micrometers) ;
- protractor (angles) ;
- profile measuring apparatus (edge) ;
- straight edge rule (flatness) ;
- three point bore gauge (internal diameter).
Only instruments which may be calibrated to primary standards should be used if optimum
accuracy is required.
7.1 Pipe sections adjacent to the primary device
For additional requirements for orifice plates, nozzles and Venturi nozzles, refer to [ISO
5167-1, 7.51. For classical Venturi tubes, refer to [ISO 5167-1, 7.61.
8

---------------------- Page: 12 ----------------------
ISO/rR 9464:1998(E)
For pipe roughness criteria, refer to the following paragraphs of [ISO 5167-I : 8.3.1,
9.1.6.1, 10.2.4.1].
7.1.1 No specific comments on this clause.
7X? No specific comments on this clause.
7.1.3 No specific comments on this clause.
7.1.4 No specific comments on this clause.
7.1.5 Internal diameter of the measuring pipe
The value of ‘ID”, corrected for thermal expansion (see below), is that used for the
computation of the diameter ratio p. This value of “D” is also used as the basis for
establishing the circularity of the pipe over a length of at least 2 D upstream and
downstream of the primary device (see 7.51).
The distance to the measurement station is expressed in terms of “D”, which is not known
before taking measurements at prescribed stations. For the purpose of establishing the
position of these stations, it is permissible to take “D” as equal to the nominal bore of the
.
pipe
Figure 1 gives an example for orifice meters where diameters are measured in only three
different cross-sections :
- A 1 ,B 1 , C, for orifice plates with corner tappings.
- A 2, B 2, C 2 for orifice plates with flange tappings.
- A 3, B 3, C 3 for orifice plates with D and D/2 tappings.
In any case, individual diameters should be measured with an accuracy of at least 0,l per
cent, as the overall tolerance is 0,3 per cent (see 7.51).
When the measuring pipe under flowing conditions is at a significantly different temperature
from the one at which diameter DO was determined (this temperature, referred to as the
reference or calibration temperature) the expansion or contraction of the pipe shall be taken
into account in the computation of diameter ratio and flow-rate, using the following equation:
(4)
D=Do[l+hD(~-To)]
where :
D : diameter of the pipe in flowing conditions ;
D : diameter of the pipe at reference temperature ;
0
.
. mean linear expansion coefficient of the pipe material ;
hg
T : pipe temperature in flowing conditions ;
T : reference or calibration temperature.
0
The value for hr, should be obtained from the manufacturer of the measuring pipe.

---------------------- Page: 13 ----------------------
@ IS0
ISO/TR 9464:1998(E)
Dimensions in millimetres
B3 c3 81
A3
B2
0 250 0,250
- m
9d---
D3x
1. Plate upstream face
2. Cross section X
Internal diameter D to be used in flowrate computation :
1
=-
+iD
D
kDiA +iDiB iC,
n n
12
i=l i=l i=l
n = 1 for corner tappings
n = 2 for flange tappings
n = 3 for D and D/2 tappings
Figure 1 : Measurement of internal diameter D
10

---------------------- Page: 14 ----------------------
ISOKR 9464: 1998(E)
@ IS0
Where automatic temperature correction is not required in the flow computer the
uncertainty for I’D” included in the overall uncertainty should be increased to allow for the
change in “D” due to temperature variation (see 11.2.2.3). An initial calculation may show
that this additional uncertainty is small enough to be considered negligible.
7.1.6 No specific comments on this clause.
7.1.7 No specific comments on this clause.
7.1.8 The requirements in [7.1.8] where drain or vent holes are located near to the primary
device are illustrated in Figure2. It should be realised that the flowing fluid may cause
deposition, corrosion or erosion of the inner wall of the pipe. The installation may therefore
not comply with the requirements of IS0 5167-I. Users should consider internal inspection
of the pipe at intervals appropriate to the conditions of application.
7.1.9 This clause is intended to ensure a reliable measurement of temperature. Although
the flowing temperature is not a quantity directly involved in the equation for calculating
flow-rate, it is an important parameter since it may be used to calculate “d” and “D” plus
critical process parameters under flowing conditions.
7.2 Straight lengths
7.2.1 When designing a metering pipe installation it is recommended that the required
minimum straight lengths are determined by the maximum diameter ratio that is expected in
the life of the installation.
For diameter ratios not covered by [ISO 5167-l) table 1 or 21 but inside the limits of the
standard, it is reasonable practice to interpolate linearly between the nearest table values
of the closest diameter ratio and to round up to the next integer number for [table I] and to
the next half number for [table 21.
If an orifice meter is designed to measure the flowrate in either direction, the minimum
straight lengths of pipe on both sides of the orifice plate shall comply with the minimum
requirements for upstreamstraight lengths as specified in [ISO 5167-1, 7.2 and Tables 1
and 21.
7.2.2 No specific comments on this clause.
7.2.3 No specific comments on this clause.
- -
7.2.4 No specific comments on this clause.
7.2.5 No specific comments on this clause.
7.2.6 No specific comments on this clause.
7.2.7 No specific comments on this clause.

---------------------- Page: 15 ----------------------
ISOER 9464:1998(E)
-
-7
Q
-
t3
2
--
~ 1 -
6 c 0,080
u
5
A
B-B
A-A
!
B
I
1. Pressure tapping
2. Row direction
3. Pressure tapping
4. Orifice plate
5. Origin holes and /or vent holes
6. Cross section A-A
7. Cross section B-B
Figure 2 : Location of drain holes and/or vent holes
12

---------------------- Page: 16 ----------------------
ISO/rR 9464:1998(E)
7.2.8 Several upstream fittings
7.2.8 (a)No specific comments on this clause.
7.2.8 (b)The requirements of this clause define the minimum straight length between the
first and second fittings in series, upstream of the primary device, except for two or more
90” bends, where the third and fourth columns of [ISO 5167-1, table 1 or 21 shall apply.
[Clause 7.41 allows the requirements of [ISO 5167-1, table 1 or 21 to be ignored if it can be
demonstrated “that the flow conditions immediately upstream (of the primary device)
sufficiently approach those of a fully developed profile and are free from swirl” [ISO 5167-l)
7.1.31.
Consideration should be given to disturbances in the flow conditions caused possibly by
additional upstream devices before the second fitting eg. a globe valve as the third fitting
would need to be sufficiently remote from the second fitting so as to present immediately
upstream of this second fitting a flow condition sufficiently close to a fully developed and
swirl free flow. No specific guidance is given in IS0 5167-l but it is recommended that the
separation of such fittings comply with the requirements of [ISO 5167-1, 7.2.8 (b)].
[ISO 5167-1, 7.2.8 (b) Note IO] also states that in the case of several 90” bends, the data
in tables 1 and 2 can be applied, whatever the lengths between two consecutive bends.
7.3 Flow conditioners
Introduction
The use of straightening devices is only recommended where it is not practicable to install
the minimum upstream straight lengths defined in [ISO 5167-1,7.2]. Nevertheless, it should
be noted that although swirl is generally not detectable in visual inspection of the pipe, it
has a greater effect on measurement than any other fluid dynamic mechanism, and may
persist over considerable distances. The use of straight lengths of pipe to eliminate swirl is
of question, especially in large pipe sizes as the degradation of induced swirl from common
pipe components may not be sufficient to ensure fully developed profiles within the
minimum lengths required in the tables.
The measurement of fluid flow by means of the primary devices described in IS0 5167-I
requires “that the flow conditions immediately upstream sufficiently approach those of a
fully developed profile and are free from swirl” (see [ISO 5167-1, 7.1.31). IS0 5167-I does
permit the use of flow straighteners in two situations :
(a) where the fittings are not defined in [table 1 and 21 ;
(b) where a large diameter ratio primary device is to be used, the installation of a flow
conditioner may allow shorter upstream lengths to be specified.
13

---------------------- Page: 17 ----------------------
ISO/rR 9464:1998(E)
Scope and field of application
For a given fitting, a flow straightener may reduce the upstream length necessary to
achieve a good velocity profile, or may improve the velocity profile for a given straight
length.
The distance between the flow straightener and the primary device, for no additional
uncertainty, is given in [ISO 5167-1, 7.3.11. The standard does not define any relaxation
permitted for any additional uncertainty, as is defined in [7.2.4] relating to the required
straight lengths, although it should be noted that the DOWNSTREAM requirements may
affect uncertainty.
7.3.1 No specific comments on this clause.
7.3.2 Type of straightening devices
New types of flow conditioners have been developed during recent years. These are not
dealt with in IS0 5167-I : 1991, which specifies five types of flow straigthener :
Other types of flow straighteners are not specified in IS0 5167-I but their use would be
permitted provided the requirements of [ISO 5167-1, 7.41 are met. Refer to IS0 7194 for
other types of flow straightener and velocity profile measurement techniques.
7.3.2.1 Type A : Zanker
Flow straighteners which give better performances often combine the characteristics of two
simple designs. Of these types, the Zanker straightener combines the “Honeycomb” and
“Perforated Plate” (see also type B). Its pressure loss is approximately 5 times the dynamic
pressure (ie. the loss of energy is about 5 times the kinetic energy due to flow velocity). It
removes both swirl and velocity profile asymmetry.
7.3.2.2 Type B : Sprenkle
This is “Perforated plate” type and specified by :
.
(a) the thickness of the plate ;
(b) the ratio of the restricted flow area to the cross-sectional area of the pipe ;
(c) the
pitch of the holes ;
(d) the bevel angle of the holes.
The spacing and diameters of the perforations are not designed to distibute the velocity
profile in line with a fully developed velocity profile.
NOTE : (c) is not defined in IS0 5167-I. Nevertheless it is recommended the holes to
be evenly distributed over the whole cross-sectional area of the pipe.
The Sprenkle straightener specified by IS0 5167-l incorporates a pressure loss of about
15 times the dynamic pressure. It is very efficient in removing profile asymmetry.
NOTE : dimension “d” is shown in some versions of [ISO 5167-1, figure 1 and figure
21 as the diameter of the bevel; it should be the diameter of the perforated hole.
14

---------------------- Page: 18 ----------------------
ISO/TR 94643 998(E)
7.3.2.3 Type C : Tube Bundle
These are specified by :
a) the length of the bundle ;
b) the diameter of the tubes ;
c) the thickness of the tubes ;
d) a minimum number of tubes.
(c) is not specified in IS0 5167-I. It should provide sufficient strength whilst not unduly
restricting the flow.
The pressure loss of the tube bundle flow straighteners as specified in IS0 5167-I is
usually low. This device eliminates practically all swirl but has little effect on the velocity
profile.
7.3.2.4 Type D : AMCA
These are specified by :
a) the length of the blades ;
b) the distance between blades ;
c) the thickness of the blades.
(c) is not specified in IS0 5167-I. It should provide sufficient strength whilst not unduly
restricting the flow.
The pressure loss of the AMCA flow straighteners as specified in IS0 5167-I varies with
the thickness of the blades, but is usually less than the dynamic pressure. This device
eliminates practically all swirl but has little effect on the velocity profile.
7.3.2.5 Type E : Etoile
These are specified by :
a) the length of the blades ;
b) the distance between blades ;
c) the thickness of the blades.
(c) is not specif
...