Study And Design Of Orifice Flowmeter Calibration Device

Air pollution is a serious threat to people’s health,and the state pays more and more attention to environmental control.Total suspended particulate matter(TSP)is one of the main culprits of air pollution and an important pollution index in air quality evaluation.In order to ensure the accuracy of environmental monitoring data,the orifice flowmeter used to calibrate total suspended particle sampler is more and more widely used,but there is no standard device specially used to test orifice flowmeter at present.In this paper,by studying the working principle of orifice flow calibration device,combined with the actual working situation,the overall design scheme of orifice flow calibration device is determined,that is,using standard meter method,using two standard meters with different principles and different measuring ranges to calibrate orifice flowmeter with different diameters and different flow ranges.In order to expand the measuring items of the device,improve the performance and strengthen the practicability of the device,the function of measuring gas flowmeter and other types of flowmeter is also designed.According to this design idea,in this paper,the hardware system of the orifice flowmeter calibration device is designed,the main components of the calibration device are selected,and the positive and negative pressure switch port input design scheme is proposed.On this basis,the development of the measurement control system of the orifice flowmeter calibration device has been completed,which can realize the functions of real-time data collection,automatic process control,data processing and record generation.In this paper,the design scheme of orifice device,mechanical structure design,measurement and control system design,device test results and uncertainty evaluation are studied in different levels.The main research contents are as follows:(1)This device is based on the standard meter method device,using two flowmeters with different flow ranges and different types as standard meters,with wide range ratio,which can cover the flow range of common orifice flowmeters in the market.(2)The mechanical structure of the device adopts parts with high accuracy and good stability to ensure the accuracy of measurement.(3)Combined with the advantages of PLC stability and reliability,in view of the orifice flowmeter calibration requirements,using GX-WORKS2 and Velonton EBPro programming language,the humanized detection interface is designed,which can output the picture report form and ensure the data is fair and reliable.(4)Flow range and uncertainty of the device:(0.4～120)m~3/h including 120 m~3/h,U_r≤0.33%,k=2;(120～160)m~3/h,U_r≤0.5%,k=2;Stability:better than 0.5%.(5)The input method of positive pressure and negative pressure switch is adopted to expand the use mode and use range of the device.