ISO 13693-2:2015 灌漑設備  —  化学療法のための安全装置  —  パート2：DN 75（3 "）からDN 350（14"）までのケミゲーションバルブアセンブリ | ページ 2

Foreword

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The committee responsible for this document is ISO/TC 23, Tractors and machinery for agriculture and forestry, Subcommittee SC 18, Irrigation and drainage equipment and systems.

ISO 13693 consists of the following parts, under the general title Irrigation equipment —Safety devices forchemigation:

• Part 1: Small plastics valves for chemington
• Part 2: Chemigation valve assemblies from DN 75 (3") to DN 350 (14")

Introduction

Chemigation is the practice of injecting chemicals into irrigation water for the purpose of distributing the chemicals onto crops. During the course of this activity, under certain hydraulic conditions, the chemicals being injected can migrate upstream into a well or other pressurized water supply and pollute that water source. A chemigation valve assembly has been developed to meet this need. The chemigation valve assembly is designed to meet the specific need and performance requirements as required to prohibit the migration of injected chemicals into irrigation wells, thereby polluting ground water supplies.

This part of ISO 13693 applies to a mainline check valve assembly in sizes from DN 75 (3”) to DN 350 (14”), with related components, that is designed to permit full flow in the operational mode and stop backflow (back siphonage or back pressure) when the pipeline shuts down. The potential for backflow from back siphonage occurs as water tumbles back down the column pipe when the pump shuts down. The potential for backflow occurs when a positive pressure exists on the downstream end of the valve. The valve obturator is forced to the closed position by a pre-tensioned spring. A resilient cover on the obturator helps to seal the valve against very low pressures.

This chemigation valve assembly is included in a technical report (to be written) that specifies a complete chemigation safety system. This system features a chemical tank (fertilizers and chemicals), a chemical pump (positive displacement or Venturi), check valves, and interlocking safety shutdown controls. The system is designed to keep irrigation water from flooding the chemical tank and to shut the chemical system down when the irrigation pump shuts down or the irrigation system pressure has been reduced to a level where the injected chemical is not being uniformly distributed to the field. The functional requirements of the chemigation valve could possibly be provided by valves of a different design. The valve is not designed for use in potable water systems.

1 Scope

This part of ISO 13693 specifies the construction and performance requirement and test methods for metal-bodied chemigation valves with water at temperatures not exceeding 50 °C, which might contain fertilizers and chemicals of the types and concentration used in agriculture.

The valve is designed to prohibit backflow caused by either back pressure or back siphonage. It is not designed for use in potable water systems. It is not to be confused with other forms of backflow prevention devices including pressure vacuum breakers, double check valves, reduced pressure zone valves, or goose neck loops. This part of ISO 13693 specifies the minimum design, construction, and performance testing requirements for the chemigation valve assembly. The assembly consists of the following components:

• a valve body into which a spring-loaded check valve is mounted with a resilient disk cover on the sealing surface;
• a combination air release/vacuum relief valve located upstream of the check valve;
• a low pressure drain valve located upstream of the check valve;
• an inspection port located so as to permit visual and manual inspection of the valve working components.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

Bibliography