ISO 9912-1:2004

INTERNATIONAL ISO
STANDARD 9912-1
First edition
2004-10-01

Agricultural irrigation equipment —
Filters for micro-irrigation —
Part 1:
Terms, definitions and classification
Matériel agricole d'irrigation — Filtres pour micro-irrigation —
Partie 1: Termes, définitions et classification




Reference number
ISO 9912-1:2004(E)
©
ISO 2004

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ISO 9912-1:2004(E)
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ISO 9912-1:2004(E)
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
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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 9912-1 was prepared by Technical Committee ISO/TC 23, Tractors and machinery for agriculture and
forestry, Subcommittee SC 18, Irrigation and drainage equipment and systems.
ISO 9912 consists of the following parts, under the general title Agricultural irrigation equipment — Filters for
micro-irrigation:
 Part 1:Terms, definitions and classification
 Part 2: Strainer-type filters
 Part 3: Automatic self-cleaning strainer-type filters
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ISO 9912-1:2004(E)
Introduction
Clogging of irrigation system components and, in particular, of drip emitters, is one of the main problems
encountered in micro-irrigation. Materials causing clogging include debris, suspended particles of organic and
inorganic origin (sand, silt, clay, plastics, algae and water-borne insects), chemical deposits (calcium
carbonate and magnesium carbonate, calcium sulphate, metal oxides and metal hydroxides) and biological
suspensions (slime secretions and fibres). Severe clogging problems are often the result of a combination of a
number of these.
The effect of the clogging materials differs according to the water source (see Annex A for a list of irrigation
water sources). With surface water supplies, water quality may also vary from one season to another and with
chemical injection. In addition, clogging hazards depend on the operating conditions, pumping regime,
irrigation system and chemical injection program.
The function of the filter in an irrigation system is to remove materials from the water that can clog or
otherwise foul the various components of the system. However, under typical irrigation conditions, and in view
of the wide range of size and hardness of suspended particles in irrigation water, complete removal of all
suspended particles cannot be expected.
Moreover, under conditions of alkaline or hard water when accompanied by conditions of high biological
activity and/or high suspended organic particle content, the materials passing through the filter are liable to
coalesce in the piping system and/or in the emitters and to cause clogging. Hence, depending on the water
quality, it could be necessary to use two or more filters in series in different parts of the system to minimize
clogging.
Under conditions of problematic water and high filtration efficiency, clogging of the filters themselves may
prove to be the main problem and completion of an irrigation set may be impeded due to the need for their
frequent cleaning.
Various operating methods, using either absorption or separation, are employed in order to separate and/or
remove clogging materials from irrigation water. In turn, separation can be by means of surface separation
(gravity surface separation, pressurized surface separation or self-circulating separation), centrifugal
separation, entrapment or interception.

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INTERNATIONAL STANDARD ISO 9912-1:2004(E)

Agricultural irrigation equipment —
Filters for micro-irrigation —
Part 1:
Terms, definitions and classification
1 Scope
This part of ISO 9912 defines terms used in relation to filters intended for agricultural micro-irrigation
systems — in particular, pressurized systems — and provides a means of classifying those filters according to
filtration method, structure, operating principle and function. It does not deal with classification according to
the type of water intended to be filtered; nor does it apply to the classification of filters for potable or domestic
water use.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
filtration
process employing a permeable medium and/or spinning component to separate, from water, materials that
would clog an irrigation system, also employing a means for removing those materials from the permeable
medium or spinning component such that the capacity of the medium or component to separate the materials
is renewed
2.2
pre-filtration
process for separating primarily large particles from water to be filtered with the object of reducing the
clogging of the filter elements and, consequently, the head loss across the filter elements
2.3
interception
method of removing suspended particles from water, by gravity, employing gravel partitions between reservoir
basins to separate the suspended particles from the water
2.4
surface separation
method of unpressurized separation that depends on gravity and employs an inclined separating element,
such as a screen, mesh or strainer, to separate suspended particles and larger clogging material from the
water
2.5
centrifugal separation
method of separation that separates, from water, clogging material heavier than water and that employs a
spinning technique using centrifugal forces exerted by the filtered water, as in a hydrocyclone
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ISO 9912-1:2004(E)
2.6
entrapment
method of filtration in which clogging material is captured within the interior of a three-dimensional filter
medium
2.7
self-circulating separation
method of filtration that employs a screen, or any other suitable filter medium, and a spinning technique used
with or without flow adjustment, for separating clogging materials from water
2.8
strainer-type filter
strainer
device containing one or more filter elements, such as a screen or mesh, used for separating clogging
materials from water flowing through the device by collecting it on the surface of the filter element, or elements
2.9
filtrate
debris, suspended particles of organic or inorganic origin, or other contaminants removed from water in the
filtration process
2.10
flushing
method of removing clogging material from a filter using water without removal of the filter element or,
following removal of the element, by manually removing clogging material from the filter element using water
2.11
back flushing
reverse flushing
method of removing filtrates from a filter by passing filtered water through the filter medium or over the surface
of the filter element, in a direction opposite to the normal flow of water, to remove accumulated, trapped or
separated filtrates from the filter, without disassembling the filter
2.12
continuous flushing
method of removing clogging material from a filter element by controlled continuous flow of purge water
2.13
through flushing
flushing by means of high-velocity, high-pressure flow through a discharge valve or outlet used for filters
especially designed for this type of flushing
2.14
simultaneous back flushing
flushing occurring simultaneously through all areas of the filter element or through all the individual elements
of a multi-element filter
2.15
sequential back flushing
back flushing of one or more individual filter elements functioning in parallel after their removal from service for
back flushing, frequently using filtered water from some or all of the remaining filter elements
2.16
directed jet flushing
flushing that employs a high-velocity stream of clean water directed at a portion of the area of a filter element
on the downstream side of the filter, thus causing a localized reverse flow that flushes the filtrate from a
portion of the filter element, and which then moves over the entire area of the element to progressively back
flush all of it
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