ISO 11738:2000 pdf download

ISO 11738:2000 pdf download.Agricultural irrigation equipment -Control heads.
4.5 Irrigation control head for measuring flow rate and/or volume
With water meter, flow meter.
See examples in Figures A.2 and A.3.
4.6 Irrigation control head for safety
With check valve, backf low preventer, vacuum relief valve or air-release valve.
See example in Figure A.5.
5 General requirements
5.1 The components comprising an irrigation control head shall comply with the relevant International Standards
(see clause 2 for the relevant International Standards in effect at the time of publication of this International
Standard).
5.2 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.
5.3 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.
5.4 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.
5.5 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.
5.6 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 comply with ISO 7-1. However, other threads are allowed provided that a suitable adaptor is supplied with each threaded connection, making it comply with ISO 7-1.
Flanges shall comply 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 water under the operating conditions specified in the relevant standards (see clause 2) for each component and type of pipe.
6.2 It is advisable, wherever possible, not to connect components and pipes made from metals with different galvanic potentials but to make the connection with a dielectric union in order to avoid electrolysis and corrosion.
6.3 Components and pipes made from plastics materials shall be opaque. Components which are exposed to ultra-violet radiation shall be externally protected or shall contain additives to improve their resistance to degradation from ultra-violet radiation under normal operating conditions.