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To achieve normal measurement accuracy, there should also be a certain length of straight pipe section upstream of the sewage flow meter sensor, although the required length is lower compared to most other flow meters. For 90o elbows, T-pipes, concentric reducers, and fully open gate valves, it is generally sufficient to have a straight pipe section with a length of 5 times the diameter (5D) away from the electrode centerline (not from the connection surface at the sensor inlet); for valves at other opening degrees, 10D is required ； The straight pipe section downstream is (2–3)D or no requirement ； But it is necessary to prevent the butterfly valve disc from extending into the sensor’s measurement tube. The lengths of the upstream and downstream straight sections specified in various standards or testing procedures also vary, with requirements that are higher than those typically applied. This is to ensure compliance with the requirements for instruments with a current precision level of 0.5. Name of the flow disturbance element; Standard or testing specification number: ISO6817, ISO9104, JISB7554, ZBN12007, JJG198. Upstream elbow, shaped tube, fully open gate valve, converging tube – 10D or as specified by the manufacturer; 10D, 5D, 5D, 10D. Converging tube can be regarded as a straight tube; for all other types of valves – 10D. Downstream: various types; no specific requirement specified; 5D, no specific requirement specified, 2D, 2D. If the valve can be used in an open position, it should be installed at an angle of 45° between its flow direction and the axis of the electrodes, which will significantly reduce additional errors. I. The concession method The so-called concession method involves making concessions regarding a certain indicator; this approach is widely used in product quality management. For example, in chemical production, the products that come out at the end of the production process do not meet the standards for first-class products, but they do meet the standards for second-class products. As a result, they are sold as second-class products instead of being discarded, which is more economical. In field applications of sewage flow meters, if the length of the straight pipe section cannot be met under any circumstances, and if the flow measurement results are not used for trade settlement but rather for general monitoring or process control, the compromise method can be attempted. II. Installation of a flow regulator A flow regulator can be used to reduce the length of the straight pipe section upstream. Compatibility tests show that it can be used downstream of any upstream fitting. Currently, only two types of flow regulators are listed in the main text of ISO 5167: the 19-tube bundle flow straightener and the Zanker flow regulator plate. The standard specifies the applicable types of throttling and flow-blocking elements as well as the exact installation locations for these flow regulators. III. Select the appropriate model Since different types of flowmeters have vastly varying requirements regarding the length of the straight pipe section, if the originally chosen flowmeter demands a long straight pipe section that cannot be satisfied under any circumstances, it is necessary to choose a model with lower requirements for the length of the straight pipe section. IV. Evaluation of the influence factors When the length of the straight pipe section is insufficient, the uncertainty of the sewage flow meter increases, as the velocity distribution within the pipe becomes distorted, resulting in the actual flow coefficient of the instrument differing from the coefficient specified at the time of factory calibration. If a flow meter equipped with upstream and downstream pipe sections is assembled using the actual types of fittings and lengths of straight pipe sections present on site, and then placed on a flow standard device to determine the flow coefficient of that instrument, it can be used accordingly; the flow coefficient can then be employed to calculate the flow rate, thereby completely eliminating the impact of insufficient straight pipe section lengths on the measurement results. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/uploadfiles/image/2011-4//2011412108214556.jpg