ISO 4064-3:2005

INTERNATIONAL ISO
STANDARD 4064-3
Third edition
2005-10-15
Measurement of water flow in fully
charged closed conduits — Meters for
cold potable water and hot water —
Part 3:
Test methods and equipment
Mesurage de débit d'eau dans les conduites fermées en pleine
charge — Compteurs d'eau potable froide et d'eau chaude —
Partie 3: Méthodes et matériels d'essai

Reference number
©
ISO 2005
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ii © ISO 2005 – All rights reserved

Contents Page
Foreword. v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 3
4 Requirements common to all tests . 3
4.1 Preliminary requirements . 3
4.2 Water quality . 3
4.3 Other reference conditions. 4
4.4 Location . 4
5 Tests to determine errors of indication. 4
5.1 General. 4
5.2 Principle. 4
5.3 Description of the test bench . 4
5.4 Pipework . 5
5.5 Calibrated reference device. 8
5.6 Meter reading . 8
5.7 Major factors affecting the determination of errors of indication . 9
5.8 Intrinsic errors (of indication). 10
5.9 Water temperature tests. 11
5.10 Internal pressure tests . 11
5.11 Flow reversal tests. 11
5.12 Irregularity in velocity fields tests. 12
5.13 Interpretation of results. 14
6 Static pressure tests. 14
6.1 Object of tests . 14
6.2 Preparation . 14
6.3 Test procedure – In-line meters . 14
6.4 Test procedure – Concentric meters . 14
6.5 Acceptance criteria. 15
7 Pressure-loss test. 15
7.1 Object of test . 15
7.2 Preparation . 15
7.3 Test procedure . 16
7.4 Acceptance criteria. 17
8 Durability tests . 19
8.1 Continuous flow test . 19
8.2 Discontinuous flow test . 21
9 Performance tests for electronic water meters and mechanical meters fitted with
electronic devices. 24
9.1 Introduction . 24
9.2 General requirements. 25
9.3 Climatic and mechanical environment .27
9.4 Electromagnetic environment . 33
9.5 Power supply. 37
10 Test programme for pattern approval. 43
10.1 General. 43
10.2 Performance tests applicable to all water meters . 44
10.3 Electronic water meters, mechanical water meters fitted with electronic devices, and their
separable parts. 44
10.4 Pattern approval of separable parts of a water meter. 44
11 Tests for initial verification . 45
11.1 General . 45
11.2 Static pressure test. 45
11.3 Error of indication measurements . 45
11.4 Water temperature of tests. 46
12 Test report. 46
12.1 General . 46
12.2 Pattern approval test report — Required contents. 47
Annex A (normative) Calculating the relative error of indication of a water meter . 50
Annex B (normative) Flow disturbance test equipment. 55
Annex C (informative) Manifold — Examples of methods and components used for testing
concentric water meters. 69

iv © ISO 2005 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 4064-3 was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits,
Subcommittee SC 7, Volume methods including water meters.
This third edition cancels and replaces the second edition (ISO 4064-3:1999), which has been technically
revised, as well as cancelling and replacing ISO 7858-3:1992.
ISO 4064 consists of the following parts, under the general title Measurement of water flow in fully charged
closed conduits — Meters for cold potable water and hot water:
⎯ Part 1: Specifications
⎯ Part 2: Installation requirements
⎯ Part 3: Test methods and equipment

INTERNATIONAL STANDARD ISO 4064-3:2005(E)

Measurement of water flow in fully charged closed conduits —
Meters for cold potable water and hot water —
Part 3:
Test methods and equipment
1 Scope
This part of ISO 4064 specifies the test methods and means to be employed in determining the principal
characteristics of water meters.
This part of ISO 4064 is applicable to cold potable water and hot water concentric and combination meters,
which can withstand maximum admissible working pressures (MAP) equal to at least 1 MPa (10 bar) 0,6 MPa
(6 bar) for meters W DN 500 mm and a maximum admissible temperature for cold potable water meters of
30 °C and for hot water meters of up to 180 °C, depending on the class.
This part of ISO 4064 also applies to water meters based on electrical or electronic principles and to water
meters based on mechanical principles incorporating electrical devices, used to meter the actual volume flow
of cold potable water and hot potable water.
In the case where water meters have a permanent flowrate of less than 160 m /h, in order to meet individual
test laboratory limitations the test schedule may make provisions for modification of the reference conditions,
when testing specifically for endurance or for performance under influence quantities.
NOTE Attention is drawn to the fact that national legislation may apply in the country of use, which will take
precedence over the provisions of this part of ISO 4064.
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.
ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions,
tolerances and designation
ISO 286-2, ISO system of limits and fits — Part 2: Tables of standard tolerance grades and limit deviations for
holes and shafts
ISO 4064-1:2005, Measurement of water flow in fully charged closed conduits — Meters for cold potable
water and hot water — Part 1: Specifications
ISO 4064-2, Measurement of water flow in fully charged closed conduits — Meters for cold potable water and
hot water — Part 2: Installation requirements
ISO 5168, Measurement of fluid flow — Procedures for the evaluation of uncertainties
ISO 7005-2, Metallic flanges — Part 2: Cast iron flanges
ISO 7005-3, Metallic flanges — Part 3: Copper alloy and composite flanges
ISO Guide to the expression of uncertainty in measurement (GUM), 1995
IEC 60068-1:1988, Environmental testing — Part 1: General and guidance
IEC 60068-2-1:1974, Environmental testing — Part 2 Tests. Tests A: Cold
IEC 60068-2-2:1993, Environmental testing — Part 2: Tests. Tests B: Dry heat
IEC 60068-2-30:1980, Environmental testing — Part 2 Tests. Test Db and guidance: Damp heat, cyclic
(12h + 12h cycle)
IEC 60068-2-31:1993, Environmental testing — Part 2 Tests. Test Ec: Drop and topple, primarily for
equipment-type specimens
IEC 60068-2-47:1999, Environmental testing — Part 2-47:Test: — Mounting of components, equipment and
other articles for vibration, impact and similar dynamic tests
IEC 60068-2-64:1993, Environmental testing — Part 2: Test methods — Test Fh: Vibration, broad-band
random (digital control) and guidance
IEC 60068-3-1:1974, Environmental testing — Part 3: Background information — Section One: Cold and dry
heat tests
IEC 60068-3-4:2001, Environmental testing — Part 3-4: Supporting documentation and guidance — Damp
heat tests
IEC 61000-4-2:1995, Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques —
Section 2: Electrostatic discharge immunity test. Basic EMC Publication
IEC 61000-4-3 Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement techniques —
Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-4:1995, Electromagnetic Compatibility (EMC) — Part 4-5: Testing and Measurement
Techniques — Surge Immunity Tests
IEC 61000-4-5:1995, Electromagnetic Compatibility (EMC) — Testing and measurement techniques —
Part 4-5: Surge immunity test
IEC 61000-4-11:1994, Electromagnetic compatibility (EMC) — Part 4-11: Testing and measurement
techniques — Voltage dips, short interruptions and voltage variations immunity tests
ENV 50204:1995, Radiated electromagnetic field from digital radio telephones. Immunity test
OIML D 4:1981, Installation and storage conditions for cold water meters
OIML D 11:1994, General requirements for electronic measuring instruments
OIML G 13:1989, Planning of metrology and testing laboratories (P 7)
2 © ISO 2005 – All rights reserved

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4064-1 and the following apply.
3.1
combination meter changeover flowrate with decreasing flow
Q
x1
flowrate occurring when the pressure drop in the combination meter increases suddenly in parallel with a
cessation of flow in the larger meter and a visible increase in flow in the smaller meter
3.2
combination meter changeover flowrate with increasing flow
Q
x2
flowrate occurring when the pressure drop in the combination meter decreases suddenly in parallel with a
start-up of flow in the larger meter and a visible reduction in the flow in the smaller meter.
3.3
relative error
ε
error, expressed as a percentage, defined by the equation:
VV−
ia
ε=×100
V
a
where
V is the indicated volume;
i
V is the actual volume.
a
NOTE More detail is provided in Annex A. ISO 4064-1 gives the maximum permissible errors.
3.4
test flowrate
mean flowrate calculated from the indication of the calibrated reference device and the test duration
4 Requirements common to all tests
4.1 Preliminary requirements
Before starting testing, a written test programme shall be compiled, and shall include, e.g. a description of the
tests for the determination of measurement error, pressure loss and wear resistance. The programme may
also define the necessary levels of acceptability and stipulate how the test results should be interpreted.
4.2 Water quality
Water meter tests shall use water. The water shall be that of the public potable water supply or shall meet the
same requirements. If water is being recycled, measures shall be taken to prevent residual water in the meter
from becoming harmful to human beings.
The water shall not contain anything capable of damaging the meter or adversely affecting its operation.
It shall not contain air bubbles.
4.3 Other reference conditions
All other applicable influence quantities, except for the influence quantity being tested, shall be held at the
following values during pattern approval tests on a water meter:
Flowrate: 0,7 × (Q + Q ) ± 0,03 × (Q + Q )
2 3 2 3
1)
Ambient temperature range: 15 °C to 25 °C
1)
Ambient relative humidity range: 45 % to 75 %
Ambient atmospheric pressure range: 86 kPa to 106 kPa (0,86 bar to 1,06 bar)
Power supply voltage (mains a.c.): Nominal voltage (U ) ± 5 %
nom
Power supply frequency: Nominal frequency (f ) ± 2 %
nom
Power supply voltage (battery): A voltage V in the range; U u V u U

bmin bmax
Working water temperature: See ISO 4064-1:2005, 5.4.1, Table 5
Working water pressure: 200 kPa (2 bar)
During each test, the temperature and relative humidity shall not vary by more than 5 °C or 10 % respectively
within the reference range.
4.4 Location
The environment chosen for the meter tests shall be in accordance with the principles of OIML G 13, and shall
be free from unintended disturbing influences, e.g. ambient temperature variation and vibration.
5 Tests to determine errors of indication
5.1 General
The method described in this part of ISO 4064 to determine measurement errors is the so-called “collection”
method in which the quantity of water passed through the water meter is collected in one or more collecting
vessels and the quantity determined volumetrically or by weighing. Other methods may be used, provided the
accuracy levels of testing stated in this part of ISO 4064 be attained.
Checking facilities of electronic devices is included in this section.
5.2 Principle
The checking of the measurement error consists of comparing the indications given by the meter under test
against a calibrated reference device.
5.3 Description of the test bench
The test bench typically consists of:
a) a water supply (mains, non-pressurized tank, pressurized tank, pump, etc.);
b) pipework;
1) When the ambient temperature and/or ambient relative humidity exceed the above-mentioned ranges, the effect on
the error of indication shall be taken into account.
4 © ISO 2005 – All rights reserved

c) a calibrated reference device (calibrated tank, reference meter, etc.);
d) means for measuring the time of the test;
e) devices for automating the test;
f) means for measuring water temperature;
g) means for measuring water pressure;
h) means for determining density, if necessary;
i) means for determining conductivity, if necessary.
5.4 Pipework
5.4.1 Description
Pipework shall include:
a) a test section in which the meter(s) is (are) placed;
b) means for establishing the desired flowrate;
c) one or two isolating devices;
d) means for determining the flowrate;
and, if necessary:
e) one or more air bleeds;
f) a non-return device;
g) an air separator;
h) a filter;
i) means for checking that the pipework is filled to a datum level before and after test.
During the test, flow leakage, flow input and flow drainage shall not occur between the meter(s) and the
reference device or from the reference device.
The pipework shall be such that at the outlet of all meters a positive pressure exists of at least 0,3 bar at any
flowrate.
5.4.2 Test section
The test section includes, in addition to the meter(s):
a) one or more pressure tappings for the measurement of pressure, of which one pressure tapping is
situated upstream of, and close to, the (first) meter;
b) if necessary, means for measuring the temperature of the water at the entry to the (first) meter.
None of the pipe components or devices placed in the measuring section shall cause cavitation or flow
disturbances capable of altering the performance of the meters or causing measurement errors.
5.4.3 Precautions to be taken during tests
The operation of the test bench shall be such that the quantity of water which has flowed through the meter(s)
equals that measured by the reference device.
Checks shall be made to ensure that pipes (e.g., the swan neck in the outlet pipe) are filled to the same datum
level at the beginning and at the end of the test.
Air shall be bled from the interconnecting pipework and the meter(s).
All precautions shall be taken to avoid the effects of vibration and shock.
5.4.4 Special arrangements for the installation of certain types of meter
5.4.4.1 Principles
The provisions of the following subclauses address the most frequent causes of error and the necessary
precautions for the installation of water meters on the test bench and are prompted by the recommendations
of OIML D 4, which aims to help achieve a test installation where:
a) the hydrodynamic flow characteristics cause no discernible difference to the meter functioning when
compared with hydrodynamic flow characteristics which are undisturbed;
b) the overall error of the method employed does not exceed the stipulated value (see 5.5.1).
5.4.4.2 Need for straight lengths of pipe or a flow straightener
The accuracy of non-volumetric water meters can be affected by upstream and downstream disturbances
caused by the presence and location of elbows, tees, valves or pumps, etc.
In order to counteract these effects, the meter under test (MUT) shall be installed between straight lengths of
pipe. The internal diameters of the upstream and downstream connecting pipework shall be the same as the
internal diameter of the water meter’s connecting ends. Moreover, it may be necessary to put a flow
straightener upstream of the straight length.
5.4.4.3 Common causes of flow disturbance
Flow can be subject to two types of disturbance, namely velocity profile distortion and swirl, both of which can
affect the accuracy of the water meter.
See ISO 4064-2 for details of installation requirements.
5.4.4.4 Volumetric water meters
Volumetric water meters (i.e., involving measuring chambers with mobile walls), such as oscillating piston and
nutating disc meters, are considered insensitive to upstream installation conditions; hence no special
recommendations are required.
5.4.4.5 Velocity type water meters
Velocity type water meters are sensitive to flow disturbance, which can cause significant errors, but the way
installation conditions affect their accuracy has not yet been clearly determined.
6 © ISO 2005 – All rights reserved

5.4.4.6 Other measuring principles
Other types of meter may or may not require flow conditioning for accuracy tests. If required, manufacturers’
recommendations shall be used during testing. Those recommendations shall be included in the pattern
approval documents.
These installation requirements should be reported in the pattern approval certificate for the water meter.
Concentric meters that are proven to be unaffected by manifold configuration (typically of the volumetric type –
see 5.4.4.4) may be tested and used with any suitable manifold arrangement.
5.4.4.7 Electromagnetic induction meters
Meters employing the principle of electromagnetic induction may be affected by the conductivity of the test
water. The test water should have a conductivity within the range of values specified by the manufacturer.
5.4.5 Test commencement and determination of errors
5.4.5.1 Principles
Adequate precautions shall be taken to reduce the uncertainties resulting from the operation of the test bench
components during the test. Details of the precautions to be taken are given in 5.4.5.2 and 5.4.5.3 for two
cases encountered in the “collection” method.
5.4.5.2 Tests with readings taken with the meter at rest
The flow is established by opening a valve situated downstream of the meter, and is stopped by the closure of
this valve. The meter should be read after registration stops.
Time is measured between the start of the opening movement of the valve and the close of the closing
movement.
While flow begins, and during the period of running at the specified constant flowrate, the error of indication of
the meter varies as a function of the changes in flowrate (measurement error curve).
When the flow is stopped, the combination of the inertia of the moving parts of the meter and the rotational
movement of the water inside the meter may cause an appreciable error to be introduced in certain types of
meter and for certain test flowrates.
NOTE In this case, it has not been possible to determine a simple empirical rule, which lays down conditions so that
this error may always be discounted as negligible. Certain types of meter are particularly sensitive to such error.
In case of doubt, it is advisable:
a) to increase the volume and duration of the test;
b) to compare the results with those obtained by one or more other methods, and in particular the method
described in 5.4.5.3, which eliminates the causes of uncertainty given above.
For some types of electronic water meters with pulse outputs, which are used for testing, the response of the
meter to changes in flowrate may be such that valid pulses are emitted after closure of the valve. In this case
means shall be provided to count these additional pulses.
Where pulse outputs are used for testing meters, a check shall be made that the volume indicated by the
pulse count corresponds to the volume displayed on the indicating device within the accuracy of registration.
5.4.5.3 Tests with the readings taken under stable flowrate conditions and diversion of flow
The measurement is carried out when the flow conditions have stabilized.
A switch diverts the flow into a calibrated vessel at the beginning of the measurement and diverts it away at
the end. The meter is read while in motion.
The reading of the meter is synchronized with the movement of the flow switch.
The volume collected in the vessel is the volume passed.
The uncertainty introduced into the volume may be considered negligible if the time to switch the flow in each
direction is identical within 5 % and if it is less than 1/50 of the total time of the test.
NOTE For combination meters the test method described in 5.4.5.3 in which readings of the combination meter are
taken at an established flowrate, ensures that the change-over device is functioning correctly for both increasing and
decreasing flowrates. The test method described in 5.4.5.2, in which readings of the meter are taken at rest, does not
allow the determination of the error of registration after regulating the test flowrate for decreasing flowrates for combination
meters.
5.4.5.4 Test method for the determination of change-over flowrates
See definitions of combination meter change-over flowrates Q and Q given in Clause 3.
x1 x2
Starting from a flowrate that is less than the change-over flowrate, Q , the flowrate is increased in successive
x 2
steps of 5 % until the flowrate Q is reached. The value of Q is taken as the average of the values of
x2 x 2
indicated flowrate just before and just after change-over occurs.
Starting from a flowrate that is greater than the change-over flowrate, Q , the flowrate is decreased in
x1
successive steps of 5 % until the flowrate Q is reached. The value of Q is taken as the average of the
x1 x1
values of indicated flowrate just before and just after change-over occurs.
5.5 Calibrated reference device
5.5.1 Overall uncertainty of the actual volume
When a test is conducted, the expanded uncertainty of the actual volume shall not exceed 1/5 of the
applicable maximum permissible error (MPE) for pattern approval, and 1/3 of the applicable MPE for initial
verification and subsequent verifications.
The evaluation and expression of uncertainty shall be made in accordance with ISO 5168 and the ISO Guide
to the expression of uncertainty in measurement (GUM), with a coverage factor k of 2.
5.5.2 Minimum volume (volume of the calibrated vessel if this method is used)
The minimum volume permitted depends on requirements determined by the test start and end effects and the
design of the indicating device (verification scale division) (see ISO 4064-1).
5.6 Meter reading
It is accepted that the maximum interpolation error for the scale does not exceed half a scale division per
observation. Thus in the measurement of a volume of flow delivered by the water meter (consisting of two
observations of the water meter), the total interpolation error can reach one scale division.
For digital indicating devices with discontinuous changes of the verification scale, the total reading error is one
digit.
8 © ISO 2005 – All rights reserved

5.7 Major factors affecting the determination of errors of indication
NOTE Variations in the pressure, flowrate and temperature in the test bench, as well as uncertainties in the precision
of measurement of these physical quantities, are the principal factors affecting the measurement of the errors of indication
of a water meter.
5.7.1 Pressure
The pressure shall be maintained at a nominally constant value throughout the test at the chosen flowrate.
For testing water meters, which are designated Q u 16, at test flowrates u 0,10 Q , the constancy of
3 3
pressure at the inlet of the meter (or at the inlet of the first meter of a series being tested) is achieved if the
test bench is supplied through a pipe from a constant head tank. This ensures an undisturbed flow.
Any other methods of supply shown not to cause pressure pulsations exceeding those of a constant head tank
may be used.
For all other tests, the pressure upstream of the meter shall not vary by more than 10 %.
The maximum uncertainty in the measurement of pressure shall be 5 % of the measured value.
Pressure at the inlet to the meter shall not exceed the maximum admissible working pressure (MAP) of the
meter.
5.7.2 Flowrate
The flowrate shall be maintained nominally constant at the chosen value throughout the test.
The relative variation in the flowrate during each test (not including starting and stopping) shall not exceed:
± 2,5 % from Q to Q (not inclusive);
1 2
± 5,0 % from Q (inclusive) to Q .
2 4
The flowrate value is the volume passed during the test divided by the time.
This flowrate variation condition is acceptable if the relative pressure variation (in flow to free air) or the
relative variation of pressure loss (in closed circuits) does not exceed:
± 5 % from Q to Q (not inclusive);
1 2
± 10 % from Q (inclusive) to Q .
2 4
5.7.3 Temperature
During a test, the temperature of the water shall not change by more than 5 °C.
The uncertainty in the measurement of temperature shall not exceed ± 2 °C.
5.7.4 Orientation of meter during error measurements
The position of the meters (spatial orientation) shall be as indicated by the manufacturer and they shall be
mounted in the test rig as appropriate.
If the meters are marked “H”, the connecting pipework shall be mounted with the flow axis in the horizontal
plane during the test (indicating device positioned on top).
If the meters are marked “V”, the connecting pipework shall be mounted with the flow axis in the vertical plane
during the test (inlet on lower end).
If the meters are not marked either “H” or “V”:
a) at least one meter from the sample shall be mounted with the flow axis vertical, with flow direction from
bottom to top;
b) at least one meter from the sample shall be mounted with the flow axis vertical and flow direction from top
to bottom;
c) at least one meter from the sample shall be mounted with the flow axis at an intermediate angle to the
vertical and horizontal (chosen at the discretion of the approving authority);
d) the remaining meters from the sample shall be mounted with the flow axis horizontal.
Where the meters have an indicating device which is integral with the body of the meter, at least one of the
horizontally mounted meters shall be oriented with the indicating device positioned at the side and the
remaining meters shall be oriented with the indicating device positioned at the top.
The tolerance on the position of the flow axis for all meters, whether horizontal, vertical or at an intermediate
angle, shall be ± 5°.
NOTE In the case of meters, where the number of meters presented for test is less than four, supplementary needed
meters will be taken from the basis population or the same meter will be submitted to different positions of test.
5.8 Intrinsic errors (of indication)
5.8.1 Test procedure
Determine the intrinsic errors (of indication) of the water meter (in the measurement of the actual volume) for
at least the following flowrates, the error at each flowrate being measured twice:
a) between Q and 1,1 Q
1 1
b) between 0,5 (Q + Q ) and 0,55 (Q + Q ) (for Q /Q > 1,6)
1 2 1 2 2 1
c) between Q and 1,1 Q
2 2
d) between 0,33 (Q + Q ) and 0,37 (Q + Q )
2 3 2 3
e) between 0,67 (Q + Q ) and 0,74 (Q + Q )
2 3 2 3
f) between 0,9 Q and Q
3 3
g) between 0,95 Q and Q
4 4
NOTE Where the initial error curve is close to the MPE at a point other than at Q , Q or Q , if this error can be
1 2 3
shown to be typical of the meter type, the approving authority may choose to define an alternative flowrate for initial
verification in the pattern approval certificate.
For each of the above:
1) test the water meter without its supplementary devices (if any) attached;
2) during a test, hold all other influence factors at reference conditions;
3) measure the errors (of indication) at other flowrates if required, depending on the shape of the error
curve;
4) calculate the relative error of indication for each flowrate in accordance with Annex A.
10 © ISO 2005 – All rights reserved

5.8.2 Acceptance criteria
5.8.2.1 The errors observed for each of the seven flowrates shall not exceed the MPEs. If the error
observed on one or more meters is greater than the MPE at one flowrate only, the test at that flowrate shall be
repeated. The test shall be declared satisfactory if two out of the three results lie within the MPE and the
arithmetic mean of the results for the three tests at that flowrate is less than or equal to the MPE.
5.8.2.2 If all the errors of the water meter have the same sign, at least one of the errors shall not exceed
one half of the MPE.
5.9 Water temperature tests
At reference conditions, the error of indication of at least one meter shall be checked at flowrate Q with the
inlet temperature held at (10 ± 5) °C and at maximum admissible working temperature, MAT, °C. The error
−5
of indication (of the meter) shall not exceed the applicable MPE.
5.10 Internal pressure tests
At reference conditions, the error of indication of at least one meter shall be checked at a flowrate of Q with
the inlet pressure held at 100 kPa (1 bar) ± 5 % and then at the MAP %. The error of indication (of the
−10
meter) shall not exceed the applicable MPE.
5.11 Flow reversal tests
5.11.1 Meters designed for reverse flow
At reference conditions, at least one meter shall be tested at the following reverse flowrates:
a) between Q and 1,1 Q ;
1 1
b) between Q and 1,1 Q ;
2 2
c) between 0,9 Q and Q .
3 3
The error of indication (of the meter) shall not exceed the applicable MPE.
One meter shall also be tested (in reverse flow) for irregularity in velocity fields, according to the provisions
of 5.12.
5.11.2 Meters not designed for reverse flow
The meter shall be subjected to a reverse flow of 0,9 Q to Q for 1 min.
3 3
The meter errors shall then be measured at the following forward flowrates:
a) between Q and 1,1 Q ;
1 1
b) between Q and 1,1 Q
2 2;
c) between 0,9 Q and Q
3 3.
The errors of indication shall not exceed the applicable MPE.
5.11.3 Meters which prevent reverse flow
The meter should be subjected to the MAP in the reverse flow direction for at least 1 min.
The meter errors shall then be measured at the following forward flowrates:
a) between Q and 1,1 Q ;
1 1
b) between Q and 1,1 Q ;
2 2
c) between 0,9 Q and Q .
3 3
The errors of indication shall not exceed the applicable MPE.
5.12 Irregularity in velocity fields tests
NOTE Some types of water meter, e.g. volumetric water meters (i.e., involving measuring chambers with mobile
walls), such as oscillating piston or nutating disc meters, have been shown to be insensitive to upstream installation
conditions. Thus in these cases, this test is not applicable.
5.12.1 Object of tests
The purpose of these tests is to verify that the meter complies with the requirements for flow profile sensitivity
(see ISO 4064-1).
NOTE 1 The effects on the error of indication of a water meter, of the presence of specified, common types of
disturbed flow upstream and downstream of the meter are measured.
NOTE 2 Types 1 and 2 disturbance devices are used in the tests to create left-handed (sinistrorsal) and right-handed
(dextrorsal), rotational velocity fields (swirl) respectively. The flow disturbance is of a type usually found downstream of
two 90° bends directly connected at right angles. A type 3 disturbance device creates an asymmetric velocity profile
usually found downstream of a protruding pipe joint or a gate valve not fully opened.
5.12.2 Preparation and test procedure
5.12.2.1 Using the types 1, 2 and 3 flow disturbers specified in Annex B, determine the error of indication
of the meter at a flowrate between 0,9 Q and Q , for each of the installation conditions specified in Figure 1.
3 3
5.12.2.2 During each test, all other influence factors shall be held at the reference conditions.
5.12.2.3 For meters where the manufacturer has specified installation lengths of straight pipe of at least
15 × DN upstream and 5 × DN downstream of the meter, no external flow straighteners are allowed.
5.12.2.4 When a minimum straight pipe length of 5 × DN downstream of the meter is specified by the
manufacturer, only tests 1, 3 and 5 shown in Figure 1 shall be performed.
5.12.2.5 Where meter installations with external flow straighteners are to be used, the manufacturer shall
specify the straightener model, its technical characteristics and its position in the installation relative to the
water meter.
5.12.2.6 Devices within the water meter having flow straightening functions shall not be considered to be a
“straightener” in the context of these tests.
NOTE Some types of water meter which have been proven to be unaffected by flow disturbances upstream and
downstream of the meter may be exempted from this test by the approving authority (see 5.12, NOTE).
5.12.3 Acceptance criteria
The error of indication of the meter shall not exceed the applicable MPE for any of the velocity field tests.
12 © ISO 2005 – All rights reserved

Test 1A Test 1B
Test 2A Test 2B
Test 3A Test 3B
Test 4A Test 4B
Test 5A Test 5B
Test 6A Test 6B
The above tests without straightener The above tests with straightener
Key
1 type 1 disturber − swirl generator sinistrorsal
2 meter
3 straightener
4 type 2 disturber − swirl generator dextrorsal
5 type 3 disturber − velocity profile flow disturber
a
Straight length.
Figure 1 — Flow disturbances scheme
5.13 Interpretation of results
5.13.1 Single test
Where the test programme specifies a single test, the meter shall pass this test if the measured error does not
exceed the MPE at the chosen flowrate.
5.13.2 Duplicated test
Where the test programme specifies that the test shall be repeated, the programme shall specify the rules to
be applied for combining the errors obtained.
The meter shall pass this test if the error resulting from this combination does not exceed the MPE at the
chosen flowrate.
6 Static pressure tests
6.1 Object of tests
The purpose of these tests is to verify that the water meter can wi
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