ISO 9635-3:2006

INTERNATIONAL ISO
STANDARD 9635-3
First edition
2006-11-15


Agricultural irrigation equipment —
Irrigation valves —
Part 3:
Check valves
Matériel agricole d'irrigation — Vannes d'irrigation —
Partie 3: Clapets antiretour





Reference number
ISO 9635-3:2006(E)
©
ISO 2006

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ISO 9635-3:2006(E)
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ii © ISO 2006 – All rights reserved

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ISO 9635-3:2006(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
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 9635-3 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 first edition of ISO 9635-3, together with ISO 9635-1, ISO 9635-2, ISO 9635-4 and ISO 9635-5, cancels
and replaces ISO 9635:1990, of which it constitutes a technical revision.
ISO 9635 consists of the following parts, under the general title Agricultural irrigation equipment — Irrigation
valves:
⎯ Part 1: General requirements
⎯ Part 2: Isolating valves
⎯ Part 3: Check valves
⎯ Part 4: Air valves
⎯ Part 5: Control valves

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INTERNATIONAL STANDARD ISO 9635-3:2006(E)

Agricultural irrigation equipment — Irrigation valves —
Part 3:
Check valves
1 Scope
This part of ISO 9635 specifies construction and performance requirements and test methods for check
valves, intended for operation in irrigation systems with water at temperatures not exceeding 60 °C, which can
contain fertilizers and other chemicals of the types and concentrations used in agriculture.
It is applicable to hydraulically operated check irrigation valves of DN 15 (1/2 inch) diameter or greater,
designed to operate in the fully open and fully closed positions, but which can also operate for extended time
periods in any intermediate position.
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 9635-1:2006, Agricultural irrigation equipment — Irrigation valves — Part 1: General requirements
ISO 9644:1993, Agricultural irrigation equipment — Pressure losses in irrigation valves — Test method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9635-1 and the following apply.
3.1
check valve
valve which automatically opens by fluid flow in a defined direction and which automatically closes to prevent
fluid flow in the reverse direction
[EN 1267]
3.2
flow coefficient
K

v
coefficient equal to the flow rate, in cubic metres per hour, of water at a temperature between 5 °C and 50 °C,
passing through the valve and causing a loss of static head of 1 bar
3
NOTE 1 QK=∆p , where Q is the flow rate in cubic metres per hour (m /h), and p is the pressure in kilopascals per
v
2
square centimetre (kPa/cm ).
5 2

NOTE 2 1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .
NOTE 3 Adapted from EN 736-3.
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ISO 9635-3:2006(E)
4 Design requirements
Check valves shall be designed in accordance with ISO 9635-1:2006, Clause 4.
Check valves may be equipped with a device to assist closure or balance the weight of the obturator.
However, such valves are not considered to have a mechanically operated obturator.
The manufacturer shall indicate in the relevant technical documentation the orientations in which the check
valves fulfil the requirements of this standard.
It is recommended that the valves be designed to permit integral repair and maintenance without removing the
valve body from the line.
5 Performance requirements
5.1 Mechanical strength
5.1.1 Resistance of shell and all pressure-containing components to internal pressure
Requirements and testing shall be in accordance with ISO 9635-1:2006, 5.1.1.
5.1.2 Resistance of obturator to differential pressure
Requirements and testing shall be in accordance with ISO 9635-1:2006, 5.1.2.
The test shall be performed with the pressure applied to the downstream side of the obturator.
After testing, the obturator shall not be jammed nor wedged. After completion of the test, the differential
pressure and flow rate necessary to fully open the obturator shall not exceed the initial values by more than
10 %.
5.1.3 Resistance of valve to bending
Requirements and testing shall be in accordance with ISO 9635-1:2006, 5.1.3.
The test shall be performed with the pressure a
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