GB/T 18691-2002 in English

《GB/T 18691-2002农业灌溉设备 止回阀》由TC201（全国农业机械标准化技术委员会）归口，TC201SC4（全国农业机械标准化技术委员会排灌设备和系统分会）执行，主管部门为中国机械工业联合会。
本标准规定了止回阀的结构、技术要求和试验方法。该止回阀用于水温不超过50℃，并且水中可能含有某些农业常用类型和浓度的肥料和/或化学物质的农业灌溉系统。

Scope

This standard specifies the structure, technical requirements and test methods of check valves. The check valve is used in agricultural irrigation systems where the water temperature does not exceed 50°C and the water may contain certain types and concentrations of fertilizers and/or chemicals commonly used in agriculture. The non-return valve described in this standard may be used in irrigation systems containing fertilizers and/or chemical substances, only referring to its corrosion resistance to these substances. This standard does not endorse check valves as backflow prevention devices to completely block reverse flow in a system. This standard applies to check valves with a nominal size of 15-300mm. This standard does not apply to backflow prevention devices that completely block reverse flow, nor does it apply to water-operated and water-operated check valves.