ISO 9644:2018

INTERNATIONAL ISO
STANDARD 9644
Third edition
2018-08
Agricultural irrigation equipment —
Pressure losses in irrigation valves —
Test method
Matériel agricole d'irrigation — Pertes de pression dans les vannes
d'irrigation — Méthode d'essai
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test installation . 2
4.1 Permissible deviation of measuring devices . 2
4.2 Test equipment . 3
4.2.1 Piping . 3
4.2.2 Throttling valve . 3
4.2.3 Flow measuring device . . 3
4.2.4 Pressure differential measuring device . 3
4.2.5 Pressure taps . 3
4.2.6 Temperature sensors . 5
4.2.7 Filtration . 5
5 Test procedure . 5
5.1 Test installation . 5
5.2 Test conditions . 5
5.2.1 Permissible fluctuations in measurements . 5
5.2.2 Steady conditions . 6
5.2.3 Unsteady conditions . 6
5.3 Test bench pressure loss . 6
5.4 Test of valve . 7
6 Test results . 7
6.1 Presentation of test results . 7
6.2 Calculated valve coefficients . 8
6.2.1 General. 8
6.2.2 Flow resistance coefficient, ζ . 8
6.2.3 Valve flow coefficient, K . 8
v
6.3 Test report . 9
Annex A (informative) Measurement uncertainty .10
Annex B (informative) Evaluation of uncertainty of flow rate coefficient, K, and pressure
v
losses coefficient, ζ .14
Bibliography .19
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
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 23, Tractors and machinery for agriculture
and forestry, Subcommittee SC 18, Irrigation and drainage equipment and systems.
This third edition cancels and replaces the second edition (ISO 9644:2008), which has been technically
revised. The main changes compared to the previous edition are as follows:
— addition of Annexes A and B.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 9644:2018(E)
Agricultural irrigation equipment — Pressure losses in
irrigation valves — Test method
1 Scope
This document applies to manually-activated valves only.
This document specifies a test method for determining the pressure loss in agricultural irrigation
valves under steady-state conditions when water flows through them. The scope and accuracy of the
valve performance specifications presented will assist agricultural irrigation system designers in
comparing pressure losses through various types of valves.
The measurement of pressure losses provides a means for determining the relationship between
pressure loss and flow rate through the valve.
This document also describes the method of reporting pertinent test data.
No attempt is made to define product use, design or applications.
The test method is suitable for valves with equal inlet and outlet nominal sizes.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at https: //www .electropedia .org/
3.1
nominal size
DN
conventional numerical designation used to indicate the size of an irrigation valve
3.2
volume flow rate
flow rate
q
V
volume of water flowing through the valve per unit time
3.3
pressure loss
Δp
difference in pressure due to water flow between two specified points in a system or in part of a system
3.4
piping pressure loss
Δp
p
pressure loss in the upstream and downstream portions of the test bench piping between the pressure
taps, but excluding the pressure loss in the valve tested (see 5.4.4)
3.5
bench pressure loss
Δp
b
head loss between the pressure taps upstream and downstream from the measurement area without
the device being tested
3.6
valve pressure loss
Δp
v
pressure loss in the valve tested
3.7
reference velocity
ν
ref
velocity of flow through the valve calculated from the actual flow rate through the valve divided by the
reference cross-sectional area of the valve
3.8
steady-state flow
state of flow where the flow rate through a cross-section does not vary with time
3.9
valve flow coefficient
K
v
number equal to the flow rate of water, in cubic metres per hour, that will flow through a fully open
valve with a one bar pressure loss across the valve
3.10
flow resistance coefficient
ζ
coefficient used in non-dimensional presentation of valve loss
4 Test installation
4.1 Permissible deviation of measuring devices
The permissible deviation of the reading indicated on the measuring devices from the actual value shall
be as follows:
flow rate: ±2 %
differential and actual pressure: ±2 %
temperature: ±1 °C
The measuring devices shall be calibrated according to the existing calibration rules in the country
performing the test.
2 © ISO 2018 – All rights reserved

4.2 Test equipment
4.2.1 Piping
Upstream and downstream piping shall be the same diameter as that of the test valve connection. The
lengths of the straight, uniform-bore pipe shall be as specified in Figure 1. The inside surface of the
piping shall be free of flaking rust, mill scale and irregularities which might cause excessive turbulence.
In that part of the test apparatus shown within the frame, in Figure 1, the order of the fittings/devices
shown in the key and the distances between them shall be adhered to, with the exception that the
lengths indicated as 5d and 10d shall be understood to be the minimum allowable lengths.
4.2.2 Throttling valve
A downstream throttling valve shall be used to control the flow through the test specimen. There are
no restrictions on the size or type of this valve. The throttling valve shall be located downstream of the
downstream pressure tap (used for measuring bench pressure).
4.2.3 Flow measuring device
Locate the measuring device at the head of the system.
If an open measuring device (such as a calibrated volumetric tank) is used, it shall be located at the
downstream end of the assembly, i.e. downstream of the downstream throttling valve.
The flow-measuring device shall be installed in accordance with the specific installation instructions and,
where applicable, shall be installed with the required length of straight piping before and after the device.
The accuracy of the measuring device shall be ±2 %.
4.2.4 Pressure differential measuring device
Any device capable of measuring pressure differential with acceptable accuracy may be used.
4.2.5 Pressure taps
Pressure taps (see Figure 2) shall be provided on piping for measurement of sta
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