Several common factors affecting orifice flow meter and methods to improve accuracy

Abstract: Several common factors affecting orifice flowmeters and methods to improve accuracy are provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. Advantages of standard orifice flowmeter: 1. Standard orifice flowmeter belongs to a type of standard throttling parts, which is universal throughout the country and has been recognized by the International Standards Organization. It can be put into use without actual flow calibration. 2. Standard orifice flow. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following are some common factors affecting orifice flowmeters and methods to improve accuracy. The article details. Advantages of standard orifice flowmeter: 1. Standard orifice flowmeter belongs to a type of standard throttling parts, which is universal throughout the country and has been recognized by the International Standards Organization. It can be put into use without actual flow calibration. 2. The structure of the standard orifice flowmeter is easy to copy, simple, firm, stable and reliable in performance and low in price; 3. The standard orifice flowmeter has a wide range of applications, including all single-phase fluids (liquid, gas, steam) , Part of the miscible flow, the pipe diameter and working state (temperature, pressure) of the general production process can be measured; 4. The detection piece and the differential pressure display instrument can be produced separately by different manufacturers, so that it can be produced on a specialized scale. 2. Disadvantages 1. The repeatability and accuracy of measurement are at a medium level in flow sensors. Due to the intricate influence of many factors, the accuracy is difficult to improve; 2. The range is narrow. Since the flow coefficient is related to the Reynolds number, the general range is only 3:1 to 4:1; 3. There is a long straight pipe length requirement, which is generally difficult to meet. Especially for larger pipe diameters, the problem is more prominent; 4. The pressure loss is large; 5. The orifice plate has an inner hole with an acute angle to ensure the accuracy, so the sensor is sensitive to corrosion, wear, scaling, and dirt, and it is difficult to ensure long-term accuracy. Dismantle and check once a year; 6. Flange connection is used, which is prone to problems of running, dripping, dripping and leaking, which greatly increases the maintenance workload. When using an orifice flowmeter, the technical requirements for orifice processing are very strict, and must comply with the provisions of national standards or ministerial standards, otherwise, it will bring errors to the measurement results of natural gas flow. (1) Protrusions in the throttling device: Gaskets, welds, etc. that extend into the pipe in the throttling device will also cause certain errors in the flow measurement. The size of the error is related to the position of the protrusion, the distance between the orifice and the protrusion, and Prominent height is related. Tests have shown that whenβ= 0.7, when the protruding object is located at 2 times the pipe diameter upstream of the orifice plate, the error is the largest; if the protruding object is located at the upstream orifice plate, the error is 16% to 50%, if the protruding object is located downstream of the orifice plate, The impact on measurement accuracy is smaller. (2) Bending of the orifice plate: Due to improper installation or maintenance, the orifice plate is bent or deformed, resulting in a large flow measurement error. The test results are carried out on the orifice plate with flange pressure, and the maximum error caused by the bending of the orifice plate is about 3.5%. (3) Orifice plate eccentricity: Experiments show that the measurement error caused by the orifice plate eccentricity is generally within 2%, and the aperture ratioβThe higher the value, the greater the influence of eccentricity, so it should be avoided.βhigh value orifice plate. (4) The front and rear straight pipe sections must meet the length requirements, that is, the distance between the first ten and the fifth, and must meet the on-site installation requirements, otherwise the measurement results of the flowmeter will also bring great errors. Ways to improve the measurement accuracy of the orifice flowmeter (1) Pipeline requirements: The national standards have strict technical requirements for the length, straight pipe, roundness and inner surface roughness of the metering tube. When the minimum length of the metering tube cannot meet the standard requirements, it will bring deviations to the flow measurement results.βIt is related to the Reynolds number, so the rectifier must be installed on the straight pipe in front of the orifice plate to ensure the measurement accuracy. (2) Installation requirements: The inlet end face of the orifice plate must be perpendicular to the axis of the pipeline, and the deviation cannot exceed 1 degree. When installing the orifice plate, pay attention to the direction of the pipeline, and it is strictly forbidden to install it in reverse. It must meet the requirements of the standard for different axial tolerances. The thickness of the gasket between the flange, the orifice plate and the pressure-taking device shall not be greater than 0.03D. The installation of the gasket shall not protrude into the straight pipe section or the inner cavity of the pressure-taking device, and shall not block the pressure-taking port and cause the change of the pressure-taking position. The orifice plate must be installed on the throttling device after the pipeline has been purged and operated for a few days to prevent the orifice plate from being damaged or polluted by liquid and solid impurities in the gas. To correctly select and use the differential pressure gauge, the differential pressure measurement process is too large and the flow rate is small. The differential pressure gauge works below 30%, which will greatly reduce the flow measurement accuracy. When the measurement flow decreases, the differential pressure gauge should be replaced in time. The size of the spring or orifice plate specifications, otherwise, the differential pressure error will be multiplied. The fundamental reason that affects the measurement accuracy of the orifice flowmeter is whether the geometry and flow state of the throttling device deviate from the design standards. Therefore, in actual use, the throttling device, orifice plate, and double corrugated differential pressure gauge should be checked and adjusted regularly in strict accordance with the design requirements, so as to reduce the measurement error and ensure the measurement accuracy. Nanjing Jinnuo Meter is a flowmeter manufacturer specializing in the production of standard orifice flowmeter series, nozzle flowmeter series; Venturi tube flowmeter series, v-cone series, and cross-section series. Welcome friends from all over the country to come and visit. The above is the whole content of this article. You are welcome to inquire about the flowmeter selection and quotation of our factory. 'Several Common Factors Affecting Orifice Flow Meters and Methods to Improve Accuracy'

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