Since flowmeters require straight pipe sections, why do some flowmeters still need valves installed before and after them?
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As the title suggests, after checking relevant information, it is known that all types of flow meters require a straight pipe section. However, some designed flow meters come equipped with valve assemblies consisting of inlet and outlet stop valves, which does not meet the requirements for a straight pipe section. Isn’t this a contradiction?
If there are shut-off valves at the beginning and end, a bypass is usually installed, primarily for maintenance purposes; in such cases, the distance between the valves is designed to meet the requirements of a straight pipe section
Well, there is a bypass, but the valve assembly on site is too compact. Also, if the requirements for straight pipe sections aren’t met, what impact will that have on the flow meter?
It’s too large; it’s impossible to measure accurately, and it may not even serve as a reference point at all – its value keeps changing
Valves are generally not full-bore, especially globe valves; even when fully opened, they do not form a straight pipe
Well, that’s true. So what if the stop valve is replaced with a ball valve?
Replacing it with a full-bore ball valve might be better
If a ball valve is used, having it fully open allows it to function as a straight pipe section; the main purpose of this is to facilitate maintenance and the replacement of the flow meter