I have a question regarding flow meters.
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It is common to see a large and a small end before and after the flow meter. Often, the flow meter used on a 100-size pipe is only 50 in size. I would like to ask everyone: How is the diameter of a flow meter calculated? Is there a ready-made formula? The same goes for control valves – is there a calculation formula? Thank you!
Original poster, the answer to this question is simple: when designing the piping systems, engineers choose a larger pipe diameter to ensure safety or to allow for future capacity expansion. However, in automated control systems, flow meters require a certain flow rate; only by reducing the pipe diameter can the flow rate be increased enough to enable the instruments to function properly.
When selecting a flow meter, the diameter of the flow meter is chosen based on the flow rate, which is why this happens.
The principle of most flow meters is to measure flow velocity; therefore, at low flow rates, most flow meters exhibit significant errors, and flow restriction is inevitable. Regulating valves also have their own calculation formulas; you can find out by searching for the relevant standards.
A flow meter can ensure measurement accuracy only within its specified measurement range, and different pipe diameters result in varying levels of measurement accuracy. Generally, the flow rate is specified by the process (normal operating flow rate, maximum flow rate, minimum flow rate). The diameter of the flow meter is selected by referring to the flow meter selection guide based on this process-specified flow rate
Thank you all. Because I majored in engineering; I don’t understand instruments. Thank you all for the explanations. But I wonder if there is a relevant formula for calculation? In this way, it is possible to understand the relevant influencing factors based on the formula.
Necking is a last resort; this situation arises due to excessive allowance in the process design. Generally, this kind of situation does not occur with throttle elements, rotors, etc.