Error Analysis and Correction of Orifice Flow Meter

Abstract: The error analysis and correction information of the orifice flow meter is provided by the excellent manufacturers of flow meters and flow meters. Abstract: Orifice flowmeter is a kind of flow measuring instrument widely used in chemical industry. It has many deficiencies in installation, use and maintenance, which are prone to errors in flow measurement. Through the study of the orifice flowmeter, the induced flow measurement is obtained. More flowmeter manufacturers choose models and price quotations. Welcome to inquire.The following is the error analysis and correction article details of the orifice flow meter. Orifice flowmeter is a flow measurement instrument widely used in the chemical industry. It has many deficiencies in installation, use and maintenance, which are prone to errors in flow measurement. Through the study of the orifice flowmeter, various causes of the flow measurement error and related elimination methods are obtained; and the measurement error is corrected by means of compensation and technical transformation, so as to ensure the accuracy and effectiveness of the flow measurement . This has a certain guiding effect on the accurate measurement of the orifice flowmeter. 0 INTRODUCTION At present, in the industrial production process, most of the flow measurement is used in conjunction with a standard throttling device orifice and a differential pressure transmitter [1-2]. Although the accuracy of the intelligent differential pressure transmitter can reach the highest level of 0.075 [3], due to various reasons, its measurement error is often large, and this problem is particularly prominent when it is used as an industrial measuring instrument. Therefore, it is of great practical significance to find out the causes of measurement errors and how to overcome them. The orifice flowmeter is mainly composed of three parts: the orifice plate, the pressure guiding pipeline and the differential pressure transmitter. The orifice plate is the throttling element of the flowmeter, which converts the medium flow into differential pressure. The differential pressure is then transferred to the positive and negative pressure chambers of the differential pressure transmitter diaphragm through the pressure guiding pipeline. offset. The measuring diaphragm is used as an electrode of the differential capacitor of the capacitive differential pressure transmitter, and forms a differential capacitor with two fixed electrodes. The left and right offset of the measuring diaphragm changes the size of the differential capacitor, and the differential capacitor is added to the circuit of the differential pressure transmitter, which is then amplified and transformed into a 4~20mA standard signal, which is displayed in the form of flow. 1. The causes and elimination methods of measurement errors Simply put, measurement errors are mainly caused by three reasons: irregular installation, untimely maintenance or misoperation, and changes in process systems or working conditions. 1.1..Irregular installation of orifice plate Although the design and calculation of the standard throttling device orifice plate is summed up through a large number of experiments [5], it can be put into use directly without actual calibration, but the following items may occur during the installation process Non-standard or even wrong situation, resulting in measurement error. The straight pipe section before and after the orifice plate does not meet the requirements: the function of the straight pipe section before and after the orifice plate is to ensure the stable flow of the fluid in the pipeline, but because there are often resistance parts such as bends, bifurcations, and confluences on the process pipeline, the fluid changes from stable to stable. disturbance, resulting in measurement errors. The solution is to reasonably design the installation position of the throttling device according to the requirements of the front and rear straight pipes. The upstream and downstream surfaces of the orifice plate are damaged or the flange gasket of the orifice plate protrudes into the pipeline: During the process of transporting the orifice plate or installing the orifice plate, it is easy to cause the upstream and downstream surfaces to be damaged or the flange gasket to protrude into the pipeline. resulting in measurement errors. The solution is to improve the technical quality and sense of responsibility of construction personnel. The construction personnel should carefully check the orifice plate before installing the orifice plate. If the upstream and downstream surfaces of the orifice plate are found to be damaged, they should replace it in time; during the process of installing the orifice plate, damage to the orifice plate should be avoided; when installing the flange gasket, use the The centerline of the flange gasket is the same as the centerline of the pipe. The upper and lower sides of the standard orifice plate are reversely installed: before installation, the flow direction of the medium in the pipeline and the direction of the orifice plate should be correctly identified, otherwise the measured value will be low. This is due to the carelessness of the construction personnel. The solution is to make the surface marked with ..+.. on the orifice plate on the upstream side of the flow direction when installing the orifice plate. .. Different orifice plates are installed in the wrong position: This situation is generally particularly prone to occur during the commissioning stage. During the commissioning stage, each process pipeline needs to be purged several times, and the orifice plate is frequently disassembled. If the size of the orifice plate is the same, there will be errors if you are not careful, and the orifice plate can be replaced to return to normal. 1.2..Irregular installation of pressure guiding pipeline The main function of the pressure guiding pipeline is to transmit the differential pressure generated by the orifice plate. Improper installation of the pressure guiding pipeline will cause additional errors on the positive and negative pressure sides of the differential pressure transmitter, resulting in measurement errors. According to general technical regulations, the laying length of the pressure guiding pipeline should be between 3 and 50m. If the pressure guiding pipeline is too short, the flow measurement fluctuates greatly; if it is too long, the measurement lag will occur. When measuring the liquid flow, the pressure guiding pipeline should be laid to ensure that the horizontal pipeline has a slope of 1..12, so that the pipeline is filled with liquid, so as to avoid measurement errors. The elimination method is to follow the technical regulations and design and construction. When measuring the steam flow, the pressure-taking ends of the condensate tanks on the positive and negative pressure sides in the pressure guiding pipeline are not of equal height. This situation creates additional static pressure errors. The elimination method is to install the condensing tank correctly to ensure the equal height of the pressure taking end. When designing the pressure taking method of the pressure guiding pipeline, it must be designed according to the relevant principles according to the difference of the measurement medium is liquid, gas or steam. In addition to paying attention to the direction of the pressure inlet, a gas collector, settler or condenser should be added according to the actual situation [6].

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