What are the standard throttling devices? What are the advantages of standard throttling devices?
The standard throttling device is a throttling device designed, manufactured and used in accordance with the technical conditions specified in the international standards ISO5167 and ISO9300 and national standards. The flow coefficient and error can be determined without the need for wet standards. Now the qualified closed pipelines are: standard orifice plate, standard nozzle, standard venturi tube, standard ratio tube, standard sonic nozzle, standard sonic nozzle, etc.; standard throttling devices in open channels are in accordance with international standards ISO5167 and ISO9300, The throttling device designed, manufactured, and used under the technical conditions stipulated by the national standard can determine the flow coefficient and error without wet standard. At present, the qualified closed pipelines include: standard orifice, standard nozzle, standard venturi tube, standard ratio trustee, standard sonic nozzle, standard sonic nozzle, etc.; open channels include: standard weirs (thin-walled weirs, triangular weirs, Rectangular weir, wide crested weir). Generally, the process of design, manufacture, installation and use can be completed according to the technical conditions stipulated by the standard without wet labeling. The following conditions must be met: 1) Determined scope of application, including medium, geometric dimensions, flow conditions, fluid mechanics parameters (Reynolds number, viscosity, pressure, temperature, etc.), thermodynamic parameters (physical properties and status), installation conditions, and data collection methods And the method of use; 2) the determined mathematical model, including the flow formula, the calculation of various related coefficients, especially the calculation of the flow coefficient; 3) the determined geometric conditions, the pipe diameter (closed pipe); the channel width (open channel); 4) Determined installation conditions, on-site conditions of various factors affecting flow; 5) Determined uncertainty calculation, additional uncertainty calculation (if necessary); 6) Determined verification period, which meets the time conditions for the performance of the flowmeter; 7) No A wet standard is needed to achieve the performance of the flowmeter. Advantages: 1) The biggest advantage is that it is economical and does not require wet labeling, which can save a lot of verification costs; 2) It is convenient to design, manufacture, install and use, and technical problems can be solved according to technical standards anytime and anywhere without causing disagreement; 3) Mature technology, easy to popularize, easy to master, and easy to use; 4) Stable and reliable; 5) Simple structure, no moving parts, long working life; 6) Suitable for various media, including liquid, gas, vapor, and multiphase; 7) Applicable to various sizes and calibers (within the standard range); 8) Applicable pressure and temperature are the highest among various flow meters; 9) A long history and the most complete accumulated test data; the most thorough theoretical research; practical experience At most; 10) There are international standards and national standards to follow. Its characteristics are listed as follows: 1) The standard lists the structure and technical requirements of the throttling device in detail; the calculation formula of the outflow coefficient and the expansibility coefficient, the application condition and the uncertainty calculation formula, etc.; the pressure loss calculation formula, etc.; the field used Conditions: pulsating flow threshold, measures to restrain insufficient development of pipe flow, such as stipulating the necessary length of the intuitive section, the installation requirements of the measuring pipe and the throttling part, and the application of the flow adjustment period. The data listed in the standards are standard throttling devices The basic data of the application is the most complete and mature among all the flow measurement standards. 2) The standard throttling device has a wealth of information about deviation from the standard for correction, such as the information listed in the AGA3 report and the references in ISO9300. In fact, there are much more information about standard throttling devices in the world. These The data we call the soft power of the standard throttling device, the soft power of the standard throttling device is second to none in the national flow detection parts. 3) The test data of the standard throttling device is jointly completed all over the world. The reliability and credibility of the data are incomparable with those completed by individual manufacturers or scientific research groups. Completed by the whole society can ensure reliable and no system deviation. . The American Petroleum Measurement Standards Manual API5.7 'Differential Pressure Flowmeter Test Protocol' stipulates that the orifice plate test piece with the RG formula outflow coefficient is the transmission standard for the dynamic traceability of the flow standard device measurement value. When reliable flow measurement value measurement is required Mesoporous plate inspection parts will play an important role. 4) In the standard throttling device, the maturity of several throttling devices is different. The nozzle of the profile throttling device and the venturi tube are worse than the orifice plate, but the profile throttling device has more than the orifice plate. The advantages, such as small pressure loss, good flow measurement stability, and suitable for dirty fluid media. In recent years, the application of these profile devices has received attention, and their use potential is far from being realized. At present, it is recommended to replace orifice plates in high-temperature and high-pressure steam measurement and mixed-phase fluid measurement. 5) The critical flow Venturi nozzle (commonly known as the sonic nozzle) has formed a boom in its application and experimental research in recent years. It is recognized as the first choice for gas flow measurement and transmission standards. The new ISO9300 standard (2005 edition) broadens its application range, mainly In areas with low Reynolds number, it can meet the needs of urban natural gas urgently in need of gas measurement and transmission standards. In addition, the high-standard sonic nozzle can raise the gas flow measurement to a new height, and its impact is very far-reaching.
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