Overview
ISO 9635-4:2014 - Agricultural irrigation equipment - Irrigation valves - Part 4: Air valves specifies construction, performance requirements and test methods for air valves used in agricultural irrigation systems. It applies to hydraulically operated, float-type air irrigation valves of DN 15 or greater, designed for water temperatures up to 60 °C and for use with fertilizers and typical agricultural chemicals. Valves covered include those with air release, air intake (vacuum relief) and air venting functions, operated directly by floats or via mechanical linkages or adjustable pilot valves.
Key topics and technical requirements
- Scope and applicability
- Float-operated (single- or double-float) air valves for irrigation pipelines.
- Suitable for water containing agricultural fertilizers and chemicals at normal concentrations.
- Design requirements
- Design to the general provisions of ISO 9635‑1; optional integrated isolating devices to ISO 9635‑2.
- Performance and testing
- Mechanical strength and pressure resistance per ISO 9635‑1 methods.
- Watertightness / seat tightness: tested with water; leakage class rate A; type tests minimum duration specified.
- Airflow characteristics: manufacturer curves (airflow vs inlet pressure) must be validated; type tests in Annex A (air release) and Annex B (air intake); catalogue values must agree within ±10% at representative points.
- Air venting (continuous): verify small-orifice area and sonic-flow capability using the AWWA M51 approach; measured results within ±10% of catalogue data.
- Chemical resistance: tested for resistance to fertilizers/chemicals as per ISO 9635‑1.
- Endurance:
- Air intake/release: 250 cycles (filling/draining) per Annex C.
- Air venting: 2 500 cycles of venting.
- Long-term unseating test: accelerated test at 50 °C and 1.2× allowable operating pressure for five days, followed by verification of normal operation and watertightness.
- Conformity assessment
- Type tests, production control and quality-system requirements following ISO 9635‑2 clauses.
- Marking & packaging
Practical applications and users
ISO 9635‑4:2014 is essential for:
- Irrigation equipment manufacturers specifying design, materials and test procedures for air valves.
- Test laboratories and certification bodies performing conformity and type testing.
- Irrigation system designers, specifiers and procurement teams who need validated performance data (air release/intake/venting) and compliance criteria.
- Quality and maintenance engineers ensuring long-term reliability in agricultural systems handling fertilized water.
Keywords: ISO 9635-4:2014, air valves, irrigation valves standard, agricultural irrigation equipment, air release, air intake, air venting, DN 15, test methods, endurance testing.
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