1. Accuracy level.The flow meter is not only used to measure the flow at the location where the installation position is, but also to monitor the leakage of pipe network and the balance of the system through the flow meter. Therefore, the accuracy level of the newly selected flow meter cannot be lower than the original flow meter, otherwise it will not only affect the measurement of the metering point but also affect the error and balance of the system.
2. Velocity range.Generally, the flow rate in the water supply network varies greatly. On the one hand, with the improvement of living standard, the per capita water consumption is constantly increasing; on the other hand, the phenomenon of concentrated water use is increasingly serious.Therefore, the flow Meter range ratio is required to be large, usually more than 40 ∶1, the best should be more than 100 ∶1, and ensure the measurement accuracy and repeatability within the range.
3. Requirements for direct pipe segment.Generally, the flow meter requires a long front and rear straight pipe section, especially the velocity flow meter requires accurate measurement under the condition that the flow state is fully developed (symmetric, state distribution).The straight section of the tubular electromagnetic flow meter should be at least the first 5D and the last 2D(D = flow meter diameter), while most velocity flow meters require the straight section to be longer.The straight pipe section of the flow meter to be selected should be similar to the original electromagnetic flow meter to ensure the measurement stability.
4. Installation and maintenance of on-line continuous flow with pressure.Conventional flow timing in the installation, maintenance, or verification of the traditional form of flow is usually interrupted flow construction, in order to avoid the trouble caused by the flow interruption, it is usually used to install bypass backup flow meters, but it requires increased equipment and civil engineering investment, and there should be enough space on the site.Therefore, the selected flow meter should be able to be installed and maintained in the case of no bypass, uninterrupted flow, and can be calibrated online.
5, do not produce pressure loss, meet the requirements of energy saving and consumption reduction part of the flow meter in the measurement process is easy to produce different degrees of pressure loss, there are problems such as too much investment, high metering cost, low pipe network efficiency, so choose the flow meter to do not produce pressure loss in the measurement process, to meet the requirements of energy saving and consumption reduction.