How to choose the nominal diameter of a flow meter

As determined by the process piping, except for throttle elements, there is generally no reduction in diameter

The nominal diameter of the flow meter is determined after selecting the flow meter based on the maximum flow rate in the process. As a result, sometimes the nominal diameter of the selected flow meter may be smaller than that of the process pipeline; in such cases, a diameter reducer is needed, but care must be taken to ensure that the required straight pipe sections for the flow meter are available.

The flow meter can have the same diameter as the pipe, or it can have a reduced diameter; it is best not to increase the diameter.

Narrowings in flowmeters are also quite common; for example, in some flowmeters where the flow rate is important, a narrowing is necessary in order to maintain the required accuracy. There is also necking to reduce costs while maintaining accuracy and flow rate

Remember that the diameter of the flow meter should not be determined based on the inner diameter of the process pipeline; instead, it should be based on the maximum flow rate, minimum flow rate, and normal flow rate. Additionally, the maximum pressure and normal pressure of the medium must also be taken into consideration； Maximum temperature, minimum temperature, as well as maximum pressure loss, and the influence of operating density and viscosity. It is best for the normal flow rate to be above 20% of the range in order to ensure measurement accuracy.

First, it is necessary to determine the type of flow meter; the selection method varies depending on the type. For most flow meters, the nominal diameter is determined based on the flow rate, such as in the case of vortex flow meters, mass flow meters, and so on； There are also some flow meters that have the same diameter as the pipeline, such as ultrasonic flow meters, etc ； There are also many flowmeters that are plug-in type and do not have a nominal diameter. I wonder which type of flow meter the poster chose?

The nominal diameter of a flow meter is determined based on the maximum and minimum flow rates of the fluid, as well as factors such as the medium’s pressure, temperature, pressure loss, density, and viscosity. Under no circumstances should process pipelines be used as a reference; during operation, the internal diameter of the flow meter is often different from that of the pipeline.

I agree with view #7: the type of instrument should be determined first, and the diameter of the flow meter should be chosen based on the maximum and normal flow rates, so that the process operating variables fall within the range of 30%–85% of the flow meter’s measurement range

The nominal diameter of a flow meter is primarily determined based on the flow rate. First, the range of the flow meter is established according to the maximum flow rate and normal flow rate required by the process. Ideally, the maximum flow rate that the flow meter can handle should be such that the normal flow rate falls within the range of 1/2 to 2/3 of this maximum value, as this ensures higher measurement accuracy. After selecting the range of the flow meter, choose the appropriate model based on the pipe diameter specifications provided by the manufacturer. For example, rotary flow meters offer two or so different diameter options for the same flow rate; you can select a diameter that is either the same as or similar to that of your process pipeline, so as to make the flow meter’s diameter as close as possible to that of the process pipeline.

It is calculated based on the maximum flow rate; of course, it is also related to factors such as medium pressure, temperature, pressure loss, density, and viscosity. This can be expressed using the formula PQ/T = P_work × Q_work / T_work, where the former represents the operating conditions and the latter refers to the working conditions.