ISO 11738:2021

INTERNATIONAL ISO
STANDARD 11738
Second edition
2021-10
Agricultural irrigation equipment —
Control heads
Matériel agricole d'irrigation — Installations de tête
Reference number
© ISO 2021
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification . 4
4.1 General . 4
4.2 Irrigation control head for filtration . 4
4.3 Irrigation control head for automation . 4
4.4 Irrigation control head for pressure or flow regulation . 4
4.5 Irrigation control head for chemigation . 4
4.6 Irrigation control head for measuring flow rate and/or volume . 4
4.7 Irrigation control head for safety . 4
5 General requirements . 4
6 Materials . 5
7 Installation of the components . .6
8 Test methods and requirements . 8
8.1 Visual inspection . 8
8.2 In situ test of resistance and watertightness under hydraulic pressure . 9
8.3 Test of operation . 9
9 Marking . . 9
Annex A (informative) Irrigation control heads — Examples .11
Bibliography .16
iii
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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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 second edition cancels and replaces the first edition (ISO 11738:2000), which has been technically
revised.
The main changes compared to the previous edition are as follows.
— New types of control heads and components of control heads were included, for example, irrigation
control head for filtration with two or more media filters.
— Symbols used in this edition were changed or revised to conform to ISO 15081:2011.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
INTERNATIONAL STANDARD ISO 11738:2021(E)
Agricultural irrigation equipment — Control heads
1 Scope
This document specifies requirements for the components and method of installation of pressurized
irrigation system control heads, referred to hereinafter as irrigation control heads, with a nominal
size of up to and including 200 mm (nominal size of an irrigation control head or nominal size of a
component).
This document is applicable only to the above-ground components of irrigation control heads for
sprinkler irrigation and micro-irrigation (mini-sprinklers, drip irrigation, etc.). It is applicable to the
basic irrigation control head, on which other irrigation control and command components (electrical,
electronic and hydraulic) can be assembled, but does not deal with these additional components.
This document is not applicable to systems and/or components that can be required to prevent the
water from freezing in the irrigation control head, such as dry-barrel hydrants or other types of
hydrants.
This document does not specify construction or operating requirements for the individual components
that make up the irrigation control head. These requirements are specified in the relevant standards
for each component.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 7-1, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances
and designation
ISO 7005-1, Pipe flanges — Part 1: Steel flanges for industrial and general service piping systems
ISO 7005-2, Metallic flanges — Part 2: Cast iron flanges
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 http:// www .electropedia .org/
3.1
activating valve
type of valve which is used to initiate and shut off the flow of water through an irrigation control head
(3.8)
EXAMPLE Manually operated valve, hydraulically operated valve, volumetric valve (3.17).
3.2
automatic self-cleaning strainer-type filter
filter with a flushing capability automatically activated by pressure differential, by duration of
infiltration, by volume of water filtered, by some other physical quantity or by any combination of these
3.3
air release valve
valve which opens automatically to allow air from the atmosphere to enter the water pipeline during
drainage of the line and/or venting of air from the water pipeline to the atmosphere during filling or
during normal operation of the pipeline under pressure
3.4
backflow preventer
mechanical assembly to prevent flow of water backwards into the distributing pipes of a water supply
system to protect against entry of substances which can constitute a health hazard
3.5
check valve
valve which permits flow of water in one direction only
3.6
fertilizer injector tank
pressure vessel connected to an irrigation system (3.9) in an in-line or on-line configuration, together
with the pipes and fittings connecting it to the irrigation system, for the purpose of injecting chemicals
into the irrigation system
3.7
water-driven chemical injector pump
hydraulic pump intended to inject chemicals into an irrigation system (3.9), powered by a single source
energy supplied by irrigation water (3.10) through a hydraulic motor, such as a piston or turbine
3.8
irrigation control head
assembly of components and pipes installed at the head of an irrigated plot which serves to control the
functioning of an irrigation system (3.9), that is, initiation and shutting off of the flow of water, pressure
regulation, water metering, filtration (3.19) and injection of chemicals
3.9
irrigation system
assembly of pipes, components, and devices installed in the field for the purpose of irrigating a specific
area
3.10
irrigation water
water of potable quality, which may contain chemicals of a type and concentration generally used in
agricultural irrigation or which is of a quality approved for use in irrigation
3.11
nominal size of an irrigation control head
numerical designation used to refer to the size of the pipe at the inlet or the outlet, whichever is smaller,
of an irrigation control head (3.8)
3.12
nominal size of a component
numerical designation used to refer to the size of an irrigation control head (3.8) which is identical to the
nominal diameter of the pipe or pipes to which the irrigation control head is intended to be connected
directly without an intermediate fitting
Note 1 to entry: A single number designation is adequate if the inlet and outlet ports are of the same size.
3.13
pressure regulator
valve in which the water passage widens or narrows automatically without an external device to
maintain the pressure at the outlet of the valve close to a pre-set value under varying pressures or flow
rates at the inlet of the valve
3.14
union
threaded coupling which is used to connect two pipes and which does not require rotation of the pipes
during assembly and disassembly
3.15
media filter
filter in which clogging material is trapped within the interior of a three-dimensional filter medium,
such as sand, gravel, textile, fibres or a porous mass of bonded particles
3.16
strainer-type filter
strainer
device containing one or more filter elements, such as a screen or a mesh, used for separating clogging
material from water flowing through the device by collecting it on the surface of the filter element or
elements
[SOURCE: ISO 9912-1:2004, 2.8]
3.17
volumetric valve
valve capable of automatically delivering pre-set volumes of water within the range of flow rates, as a
result of measuring the volume of water flowing through the valve
[SOURCE: ISO 7714:2018, 3.1]
3.18
pressure regulation
reduction of pressure prevailing in a supply line to maintain it at a relatively constant pre-set value in
an irrigation system (3.9)
3.19
filtration
process which employs a permeable medium and/or a spinning component to separate, from water, any
materials that would clog an irrigation system (3.9) and which also employs a means for removing these
materials from the permeable medium or the spinning component in order to renew the capacity of the
permeable medium or the spinning component to separate these materials from the water
3.20
chemigation
injection of chemicals, including fertilizers, into irrigation water (3.10) and conveyance of these
chemicals to plants
3.21
automation
methods and means of activating or terminating operation of an irrigation system (3.9) or of changing
its operating conditions according to a preconceived plan and without manual intervention
3.22
flow regulation
function intended to control the flow rate of water to reduce it to that required in an irrigation system
(3.9) and maintain it at a relatively constant value
4 Classification
4.1 General
Irrigation control heads are classified according to their main function, as indicated in 4.2 to 4.7.
NOTE Most irrigation control heads fulfil a number of functions simultaneously. The following classification
is made principally in order to facilitate reference to these functions in this document.
4.2 Irrigation control head for filtration
Strainer-type filter, automatic filter, media filter, etc.
See examples in Figures A.1, A.3, A.4, A.5 and A.6.
4.3 Irrigation control head for automation
Volumetric valve-controlled, hydraulically operated, electrically operated, electronically operated,
computer-controlled, etc.
See examples in Figures A.2 and A.3.
4.4 Irrigation control head for pressure or flow regulation
See examples in Figures A.2 and A.3.
4.5 Irrigation control head for chemigation
With chemical injection tank unit or electrically or hydraulically operated chemical injection pump.
See example in Figure A.6.
4.6 Irrigation control head for measuring flow rate and/or volume
With water meter, flow meter.
See examples in Figures A.2 and A.3.
4.7 Irrigation control head for safety
With check valve, backflow preventer, vacuum relief valve or air-release valve.
See example in Figure A.6.
5 General requirements
5.1 The irrigation control head shall be located in a place which is convenient for access and
operation, free from weeds or other objectionable growth, such as tall brush and heavy vines, and
which is protected from accidental mechanical damage by vehicles, tractors or livestock, and fire.
In medium-textured and fine-textured soils, or in poor drainage conditions, gravel or a similar material
shall be spread around the area of the irrigation control head in order to avoid accumulation of mud and
maintain stable soil conditions around the irrigation control head. Alternatively, the irrigation control
head may be assembled on a rigid platform made of concrete or other suitable material.
Drainage facilities shall be provided in the area of the irrigation control head, especially for those
irrigation control heads that contain a filtration device, a chemical injector pump or tank, or a
discharging backflow preventer.
The drainage shall be such that spills of chemicals or irrigation water containing injected chemicals
cannot return directly to ground or surface water supplies and shall contain them in an environmentally
sound manner.
The irrigation control head shall be installed in a manner to prevent access to it by children or
unauthorized persons who might tamper with the components or with the chemicals. This can be
accomplished with fenced enclosures or locking mechanisms on the various components and containers.
5.2 The height of the installation shall provide for convenient disassembly and assembly of the
various components for the purpose of cleaning, repair and replacement while preventing entry of dirt
or debris into the irrigation system. The components shall be installed at a minimum height of 0,4 m
above the ground surface. This requirement does not apply to system components standing on the
ground surface such as media filters.
5.3 Irrigation control heads shall be supported to prevent or reduce structural stresses in their
components and to prevent vibration of the irrigation control heads during operation.
The required stabilization shall be obtained by a thrust block at the inlet and outlet pipes and/or
suitable supports, if necessary, especially beneath the heavy components of the irrigation control head.
5.4 The distance of the different components of the irrigation control head from each other shall
be sufficient to ensure reliable function of meters and gauges in accordance with manufacturer
requirements and to facilitate operation of the system, maintenance and cleaning of filters and
dismantling and replacement of those parts which are replaceable in the field. The exposed length of
the threaded nipples after their assembly shall be sufficient to enable convenient gripping with a pipe
wrench.
Water meters shall be installed in accordance with the general specifications concerning these meters.
5.5 The components of an irrigation control head shall be connected to the piping by means of
threads, flanges or other suitable means of connection.
Threads of components for connection of the irrigation control head to the irrigation pipeline shall
conform with ISO 7-1. However, other threads are allowed provided that a suitable adaptor is supplied
with each threaded connection, making it conform with ISO 7-1.
Flanges shall conform with ISO 7005-1 or ISO 7005-2.
6 Materials
6.1 The pipes and components from which the irrigation control head is assembled shall be made of
materials resistant to irrigation
...