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STANDARD
First edition
1992-I 2-l 5
Agricultural irrigation equipment - Filters -
Part 3:
Automatic self-cleaning strainer-type filters
Mat&-iel agricole d’irrigation - Filtres -
Par-tie 3: Filtres i? tamis ZI autonettoyage automatique
Reference number
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IS0 9912-3:1992(E)
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IS0 9912=3:1992(E)
Foreword
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, govern-
mental 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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an lnter-
national Standard requires approval by at least 75 % of the member
bodies casting a vote.
International Standard IS0 9912-3 was prepared by Technical Committee
ISO/TC 23, Tractors and n,achinet-y for agriculture and forestry, Sub-
Committee SC 18, irrigation and drainage equipment and systems.
IS0 9912 consists of the following parts, under the general title Agricul-
tural irrigation equipment - Filters:
- Part 1: Classification
- Part 2: Strainer-type filters
- Part 3: Automatic self-cleaning strainer-type filters
0 IS0 1992
All rights reserved. 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
Printed in Switzerland
ii
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IS0 9912=3:1992(E)
INTERNATIONAL STANDARD
Agricultural irrigation equipment - Filters -
Part 3:
Automatic self-cleaning strainer-type filters
3.1 automatic self-cleaning strainer-type filter: Fil-
I Scope
ter having automatic flushing capability as deter-
mined by pressure differential, duration of filtration,
This part of IS0 9912 specifies the general con-
volume of water filtered, or by some other physical
struction requirements and test methods for auto-
quantity or by any combination of these.
matic self-cleaning strainer-type filters (hereinafter
called filters), intended for operation in agricultural
3.2 duration of automatic flushing cycle of filter:
irrigation systems.
Period of time during which water and dirt is flushed
It does not cover filtration ability, efficiency and ca-
out of the filter via the flushing valve during each
pacity (quality of filtration water, time of operation
automatic flushing cycle.
before filter becomes entirely clogged, etc.).
3.3 flushing control mechanism: Mechanism which
NOTE 1 IS0 9912-2 covers strainer-type filters in gen-
controls the flushing action of the filter, as deter-
eral.
mined by one or a combination of physical quanti-
ties, such as pressure differential, duration of
filtration, volume of water filtered, etc.
2 Normative references
The following standards contain provisions which, 3.4 flushing pressure differential: Pressure differ-
through reference in this text, constitute provisions
ential between two points, one upstream and one
of this par-t of IS0 9912. At the time of publication,
downstream of the filter element, which initiates the
the editions indicated were valid. All standards are
flushing cycle.
subject to revision, and parties to agreements based
on this part of IS0 9912 are encouraged to investi-
3.5 flushing valve: Valve through which flushing
gate the possibility of applying the most recent edi-
water is discharged from the filter.
tions of the standards indicated below. Members of
IEC and IS0 maintain registers of currently valid
This is not the same valve as that defined in
NOTE 2
International Standards. IS0 9912-2:1992, definition 3.6 “drain valve; flush valve”.
IS0 2859-l : 1989, Sampling procedures for inspection
3.6 minimum working pressure: Lowest working
by attributes - Part I: Sampling plans indexed by
pressure declared by the manufacturer which en-
acceptable quality level (AQL) for lot-by-lot in-
sures the proper functioning of the device (auto-
spection.
matic self-cleaning strainer-type filter, valve, etc.)
without an additional high-pressure source.
IS0 9912-211992, Agricultural irrigation equipment --
Filters
- Part 2: Strainer-type filters.
3.7 preliminary filter element: Body having larger
aperture openings than the filter element, designed
to protect the cleaning mechanism.
3 Definitions
3.8 protective mechanism: Mechanism that pre-
For the purposes of this part of IS0 9912, the defi-
vents repeated flushings of a filter caused either by
nitions given in IS0 9912-2 and the following defi-
mechanical failure in the flushing controt mech-
nitions apply.
1
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IS0 9912=3:1992(E)
anism or by some other factor defined the
bY
manufa cturer.
3.9 volume of flushing water: Volume of water
flushed from the filter during one flushing cycle.
4 Marking
Each filter shall bear all the markings specified in
IS0 9912-23992, clause 4. The filter markings shall
also include a notched scale which shows the indi-
vidual setting, where these exist, for the possible
choices of adjustment of the automatic self-cleaning
cycle.
Key
5 General requirements
1 Inlet
All the requirements specified in IS0 9912-2 apply to
2 Outlet
automatic self-cleaning strainer-type filters, in addi- 3 Stralner (tllter) housing
4 Strainer (filter) housing cover
tion to the requirements and tests specified in this
5 Fflter element
part of IS0 9912.
6 Flushing valve
7 Filter tlushlng control mechanism
Figure 1 - Typical automatic self-cleaning
6 Technical characteristics
strainer-type filter
A model of a typical automatic self-cleaning strainer
filter is given in figure 1.
In addition, the following construction features are
The construction of an automatic self-cleaning
recommended.
strainer-type filter shall comply with the following
specific requirements.
f) The filter may be fitted with a device to enable
adjustment of the preset value of the filter flush-
a) The flushing control mechanism shall be in-
ing control mechanism for activation of the
cluded as part of the filter assembly and shall be
flushing control mechanism and for control of the
supplied by the manufacturer together with the
duration of the automatic flushing cycle of the
filter.
filter.
b) The filter control mechanism shall permit manual
g) The filter may be equipped with a protective
flushing at any time, irrespective of the con-
mechanism that prevents repeated flushings
ditions that apply to automatic flushing.
(see 3.8).
c) The construction of the filter shall allow for man-
h) It is recommended that all the hydraulically op-
ual operation in the event of failure of the auto-
erated accessories of the filter should be oper-
matic flushing control mechanism.
ated by filtered water, with the exception of the
inlet pressure signal which may come from the
d) The construction of the filter body shall permit
prefiltered water.
dismantling for maintenance (or for cleaning if
the filter is also designed for manual cleaning).
7 Sampling and acceptance requirements
e) The coordination of the cleaning operation and
The type-tests and acceptance tests shall be as
the opening of the flushing valve shall prevent
specified in 7.1 and 7.2, and tables 1 and 2. [Table 1
water flowing out of the flushing valve unless the
is a repetition for convenience from IS0 9912-2:1992
filter is being cleaned; no cleaning shall be
(table 2).]
possible unless the flushing valve is open.
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IS0 9912=3:1992(E)
defective specimens found in the test does not ex-
7.1 Type-tests
ceed the acceptance number specified in
IS0 2859-l :I 989.
If the filters are produced as a regular product se-
ries, the test specimens shall be taken at random
For the other tests, the number of test specimens
by the representative of the test laboratory from a
shall be selected at random from the sample in ac-
quantity of at least 20 automatic self-cleaning
cordance with tables I and 2. The shipment or
strainer-type filters. The number of test specimens
manufacturing lot is considered to comply with this
required for each test shall be as specified in tables
part of IS0 9912 if the number of defective speci-
1 and 2.
mens found in the other tests does not exceed the
acceptance number specified in tables 1 and 2.
If the filters are not produced as a regular pro-
duction series and the number of filters produced is
less than 20, no requirement is stipulated as to the
Table 2 - Required number of test specimens and
sampling procedure.
acceptance number
If the number of defective specimens in the sample
No. of
is equal to or less than the acceptance numbers test Acceptance
Clause’) Name of test
speci- No.
shown in tables 1 and 2, the lot shall be accepted.
mens
If the number of defective specimens in the sample
is greater than the acceptance number, the lot shall
8.1 .I Volume of flushlng water 3 0 [8.1.1 a)]
be rejected.
and duration of flushing
1 [8.1.1 b)]
8.1.2 Volume of flushing water 2 0
Table 1 - Required number of test specimens and
and duration of flushing
acceptance number
8.2 Flushing control mech-
anism
Accept-
No. of test
8.2.1 Mechanism activated 3 1
Clausel) Name of test ante
specimens
by pressure differen-
No.
tial sensor
8.2.2 Mechanism activated 3 1
7.2*) Resistance of strainer to 3 13)
by duration of oper-
internal hydrostatic press-
ation
ure
8.2.3 Mechanism activated 3 1
3 13)
7.3 Resistance of strainer to
by volume of filtered
internal hydrostatic press-
water
ure at high temperature
8.2.4 Mechanism activated 3 1
7.4 Resistance of filter element 2 0
by some other physi-
to buckling or tearing
cal quantity
7.5 Tightness of filter element 3 0
8.3 Test of protective mech- 2 0
7.6 Clean pressure drop 1 0
anism
1 0
9.2 Tests following com-
All clause numbers in this table refer to IS0 9912-2:1992.
I)
pletion of simulated-use
2) For metal-body strainers, see IS0 9912-2:1992, sub- performance test
clauses 7.2.1 and 7.2.2; for plastics body strainers, see IS0
Visual test 1 0
9.2.2
9912-2:1992, subclauses 7.2.1
...