Detail of GB/T 19794-2023

Introduction of GB/T 19794-2023

GB/T 19794-2023 Agricultural irrigation equipment - Volumetric valves - General requirements and test methods 1 Scope This document specifies general requirements and test methods for volumetric valves able to automatically deliver preset quantities of water. It is applicable to valves actuated by pipeline pressure and flow alone, and which do not need any other, external, source of energy. Note: Volumetric valves are typically required to operate correctly with different qualities of irrigation water at a variety of flow rates and at temperatures between 5 °C and 50 °C. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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. GB/T 40115-2021 Meters for irrigation water (ISO 16399:2014, IDT) ISO 7-1 Pipe threads where pressure-tight joints are made on the threads - Part 1: Dimensions, tolerances and designation Note: GB/T 7306.1-2000, Pipe threads with 55 degree thread angle where pressure-tight joints are made on the threads - Part 1: Parallel internal and taper external threads (eqv ISO 7-1:1994) GB/T 7306.2-2000, Pipe threads with 55 degree thread angle where pressure-tight joints are made on the threads - Part 2: Taper internal and external threads (eqv ISO 7-1:1994) ISO 9644 Agricultural irrigation equipment - Pressure losses in irrigation valves - Test method Note: GB/T 18688-2012, Agricultural irrigation equipment – Pressure losses in irrigation valves - Test methed (ISO 9644:2008, IDT) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 volumetric valve valve capable of automatically delivering preset volumes of water within the range of flow rates, as a result of measuring the volume of water flowing through the valve 3.2 serial volumetric valve volumetric valve (3.1) designed to operate in a sequence of volumetric valves 3.2.1 single outlet serial volumetric valve serial volumetric valve (3.2) with one inlet and one outlet, intended for connection in parallel in a system of volumetric valves designed to be opened by means of a hydraulic command when preset to the open position and which, on closing after delivering a preset volume of water, transmits a hydraulic command to the next volumetric valve in the system to bring it into operation 3.2.2 single outlet “skip over” serial volumetric valve serial volumetric valve (3.2) with one inlet and one outlet, intended for connection in parallel in a system of volumetric valves designed to be opened by means of a hydraulic command when preset to the open position and which, on closing after delivering a preset volume of water, skips over the next volumetric valve in the system and transmits a hydraulic command to the second next volumetric valve to bring it into operation 3.2.3 dual outlet serial volumetric valve serial volumetric valve (3.2) with one inlet and two outlets, normally open when the pressure at the inlet is the atmospheric pressure and designed so that, when a preset volume of water has passed through the first outlet, this outlet closes automatically, the second outlet opens automatically and all the flow is passed through the second outlet to the next volumetric valve in the series 3.3 non-serial volumetric valve volumetric valve (3.1) designed to operate alone 3.4 permanent flow rate qV3 highest flow rate within the rated operating conditions at which the meter is designed to operate in a satisfactory manner within the maximum permissible error 3.5 overload flow rate qV4 highest flow rate at which the water meter is designed to operate for a short period of time within its maximum permissible error, whilst maintaining its metrological performance when it is subsequently operated under normal service conditions 3.6 minimum flow rate qV1 lowest flow rate at which the volumetric valve (3.1) is designed to operate within the maximum permissible error 3.7 range of flow rate flow rate between the minimum flow rate (3.6) and the overload flow rate (3.5), inclusive of limits 3.8 range of working flow rate flow rate between the minimum flow rate (3.6) and the permanent flow rate (3.4), inclusive of limits 3.9 relative error ε difference between measured and actual volume divided by actual volume, expressed as a percentage 3.10 maximum working pressure highest pressure immediately upstream from a device recommended by the manufacturer to ensure continuous operation and functionality 3.11 minimum working pressure lowest water pressure at the inlet to a volumetric valve (3.1) at which it operates satisfactorily and performs the mechanical and hydraulic functions as specified by the manufacturer 3.12 range of working pressures pressures between and including the minimum working pressure (3.11) and the maximum working pressure (3.10) 3.13 nominal pressure pressure numerical designation equal to the maximum working pressure (3.10) specified by the manufacturer 3.14 accuracy quality which characterizes the ability of a measuring instrument to give indications approximating to the true value of the quantity measured 3.15 uncertainty of measurement parameter associated with the result of a measurement, obtained using an appropriate mathematical formula which takes into account all sources of error, that characterizes the dispersion of values that could reasonably be attributed to the measurement result 3.16 pattern approval certification bestowed by an authorized and accepted body, recognizing that the pattern of a measuring instrument conforms to the requirements of accepted International Standards 3.17 granulometry measure of the particle (grain) content of irrigation water, as characterized by size dispersion and total amount of solids 4 Classification 4.1 According to accuracy of cumulative volume counter Class 1: Volumetric valve containing a control mechanism with a cumulative volume counter and having an accuracy of volume measurement of ± 2 %, within the range of flow rates. Class 2: Volumetric valve containing a control mechanism with a cumulative volume counter and having an accuracy of volume measurement of ± 4 %, within the range of flow rates. Classes 1 and 2 are recommended for water measurement in agricultural irrigation applications. Class 3: Volumetric valve containing a preset volume mechanism but without a cumulative volume counter. 4.2 According to method of operation as a system of volumetric valves 4.2.1 Non-serial volumetric valve. 4.2.2 Serial volumetric valve: ——single outlet serial volumetric valve; ——single outlet “skip over” serial volumetric valve; ——dual outlet serial volumetric valve. Note: The opening and closing commands of the water in the inlet of the first valve in the system can be either manual or automatic.

Contents of GB/T 19794-2023