1. The influence of upstream and downstream straight pipe segment on the measurement accuracy of ultrasonic flowmeter. The calibration coefficient K is a function of Reynolds number. When the flow velocity is uneven from laminar flow to turbulent flow, the calibration coefficient K will change greatly, resulting in the decrease of measurement accuracy. According to the requirements of use, the ultrasonic flow meter transducer should be installed in the upstream straight pipe section of 10D, the downstream straight pipe section of 5D position, for the upstream presence of pumps, valves and other equipment when the length of the straight pipe section, the requirements of “distance from turbulence, vibration, heat source, noise source and ray source as far as possible”. If there are pumps, valves and other equipment upstream of the installation position of the ultrasonic flow meter transducer, the straight pipe section is required to be more than 30D. Therefore, the length of the straight pipe section is the main factor to ensure the accuracy of the measurement.
2. The influence of pipeline parameter equipment on the measurement accuracy of ultrasonic flowmeter. The accuracy of pipeline parameter setting is closely related to the measurement accuracy. If the setting of the material and size of the pipeline is inconsistent with the actual, it will cause an error between the theoretical pipeline flow cross-sectional area and the actual flow cross-sectional area, resulting in inaccurate final results. In addition, the emission spacing between the ultrasonic flow meter transducer is the result of comprehensive calculation of various parameters such as fluid (sound velocity, dynamic viscosity), pipeline (material and size), and the installation method of the transducer, etc., and the installation distance of the transducer deviates, which will also cause large measurement errors. Among them, the setting and installation distance of the inner warp of the pipeline have a prominent influence on the measurement accuracy. According to the relevant data, if the internal longitude error of the pipeline is ±1%, it will cause about ±3% flow error; If the installation distance error is ±1mm, the flow error will be within ±1%. It can be seen that only with the correct setting of pipeline parameters can the ultrasonic flowmeter be installed accurately and the influence of pipeline parameters on measurement accuracy can be reduced.
3, the influence of ultrasonic flow meter transducer installation position on measurement accuracy. There are two ways to install the transducer: reflection type and direct type. If the use of direct mounting sound speed travel is short, the signal strength can be enhanced.
4. Influence of coupling agent on measurement accuracy. In order to ensure full contact with the pipeline, when installing the transducer, a layer of coupling agent needs to be evenly coated on the surface of the pipeline, and the general thickness is (2mm – 3mm). The bubbles and granules in the coupler are removed so that the emitter surface of the transducer is tightly attached to the tube wall. Flowmeters for measuring circulating water are mostly installed in Wells, and the environment is humid and sometimes flooded. If a general coupling agent is used, it will fail in a short time, affecting the measurement accuracy. Therefore, special waterproof coupler must be selected, and the coupler should be used within the effective period, generally 18 months. To ensure measurement accuracy, the transducer should be reinstalled every 18 months and the coupler should be replaced.
Post time: Sep-04-2023