Error Generation and Correction Method of Orifice Flow Meter

Abstract: The information on the error generation and correction method of the orifice flowmeter is provided by the excellent flowmeter and flowmeter manufacturers. The reasons for the measurement error of the orifice flowmeter and how to eliminate it: Simply put, the measurement error is mainly caused by: 1. irregular installation, 2. untimely maintenance or misoperation, 3. process system or change of working conditions. 1.1..Orifice plate installation is not standardized though. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following are the details of the error generation and correction methods of the orifice flowmeter. The reasons for the measurement error of the orifice flowmeter and the way to eliminate it: Simply put, the measurement error is mainly caused by three reasons: 1. improper installation, 2. untimely maintenance or misoperation, 3. process system or change of working conditions. 1.1..Irregular installation of the orifice plate Although the design and calculation of the orifice plate of the standard throttling device is summed up through a large number of experiments, it can be directly put into use without actual calibration, but the following irregularities may occur during the installation process. error conditions, resulting in measurement errors. 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. 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 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. 2. The installation of the differential pressure transmitter is not standardized. The installation environment of the differential pressure transmitter is too poor, such as large vibration, large dust or strong corrosive medium. The elimination method is to install the transmitter in a suitable location according to the relevant technical regulations; if it must be installed in a special environment, protective measures should be added according to the actual situation of the site, such as adding a protective box or a fixed bracket. 3. 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 the positive and negative pressures of the differential pressure transmitter, resulting in additional errors, 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]. 4. When the pressure guiding pipe is blocked or leaking to measure the viscous and easy-to-crystallize medium, the pressure guiding pipe and the stop valve are often blocked due to heat tracing and other reasons, so that the differential pressure value input to the differential pressure transmitter changes, resulting in Measurement error. The elimination method is regular inspection, sewage cleaning or manual pump dredging. When measuring high pressure or corrosive media, leakage of pressure guiding pipes or joints often occurs, resulting in pressure loss and differential pressure deviation. The solution is to inspect regularly and plug the loopholes. 5. The orifice plate is deformed or fouled. The orifice plate is not removed in time during the commissioning and purging process, and is impacted and deformed by the debris in the pipeline; the orifice plate has been corroded and washed by the process medium for a long time, resulting in a certain degree of deformation. The deformation of the orifice plate makes the differential pressure value generated by the orifice plate deviate. The way to eliminate it is to disassemble and inspect regularly, and replace it in time if it is found to be deformed.

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