What factors affect the measurement accuracy of orifice flowmeter sensors?

The orifice flow sensor is a high range ratio differential pressure flow device that combines a standard orifice plate with a multi-parameter differential pressure transmitter. It can measure the flow of gas, steam, liquid and natural gas, and is widely used in process control and measurement in the fields of petroleum, chemical industry, metallurgy, electricity, heating, water supply, etc. In actual use, if you do not pay attention to the following points, it will affect the measurement accuracy of the orifice flow meter sensor.

　　1. Characteristics of the fluid being measured

　　Due to the nature of natural gas itself, it will undergo complex changes with changes in the external ambient temperature, thus affecting the measurement accuracy of the flow sensor. For natural gas measurement, the operating temperature and pressure of the natural gas must be determined first, because changes in the external temperature will cause changes in the pressure and temperature of the natural gas itself, which may cause excessive changes in density and compression coefficient. Low-density gas presents difficulties for certain measurement methods. At this time, the selected measurement method must be changed, or temperature and pressure corrections must be made to ensure the accuracy of the sensor measurement.

　　2. Impact of instrument performance

　　The main causes of errors caused by the orifice flowmeter sensor itself are: the sharpness of the right angle of the orifice inlet; the pipe diameter size does not match the calculation; the orifice thickness error; the throttling device accessories produce steps and eccentricity; the flatness of the upstream end face of the orifice; the ring chamber size produces steps and eccentricity; the pressure taking position; welding, weld protrusion; the pressure taking hole is not processed in a standardized or blocked manner; the throttling device is not axially consistent, etc. These factors may affect the repeatability of the orifice plate. Repeatability is determined by the principle and manufacturing quality of the instrument itself, and it is an important indicator in process control applications. In addition to repeatability, accuracy is also related to the value calibration system. In practical applications, the excellent repeatability of the instrument is disturbed by many factors, including changes in fluid viscosity, density, etc., which will affect the measurement accuracy. If the output characteristics of the instrument are nonlinear, this effect is more prominent.

　　3. Impact of installation

　　Installation errors caused by deviations in pipeline layout are common, and the main reason for this is that the required length of the straight pipe section cannot be met on site.

　　IV. Impact of Environmental Conditions

　　Although the flow sensor can be installed and used normally, the environmental conditions of use have changed from the expected conditions, so some performance parameters and hardware aspects of the instrument have also changed, which will change the measurement results of the orifice flowmeter sensor.