The issue of the nominal diameter of flow meters in relation to the pipe diameter
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For a DN50 pipeline carrying liquid chlorine at a flow rate of 2.2 m3/h, a DN25 mass flow meter was selected. Is it appropriate to install a DN25 mass flow meter on a DN50 pipeline? Also, I checked the flow meters produced by the manufacturer – their range meets the requirements. Would it be appropriate to use a DN15 flow meter on a DN50 pipeline? Are there any requirements or things to note for this?
The selection of flow meters is generally consistent with that of the process pipelines; it can also be one size smaller. However, if it is too small, it will increase pipeline resistance, and it is unclear whether this will affect the process.
Why use DN15? Saving money? Let me tell you, it doesn’t necessarily save money – a small diameter means high pressure losses, and the annual energy loss costs can exceed the cost of the meter itself.
Is it a flow meter or a control valve? Flow meters are generally about the same size as the pipe diameter, at most one size smaller. As for the control valve, it can be much smaller.
The nominal diameter of the flow meter also determines the flow range of this flow meter
For DN50 pipes, it is best to choose a flow meter with the same diameter (to reduce pressure loss); only if that is not possible should considering a reduced diameter be considered.
It is specified in the standard JB/T6844-1993 \"Metal Tube Float Flowmeter\"
Mass flow meter manufacturers have specialized calculation software; ask them to carry out the calculations
Personal opinion: 1. The diameter of the flow meter can definitely be smaller than the nominal diameter of the pipeline. For mass flow meters, it can be much smaller, as it has almost no requirements regarding straight pipe sections. The float flowmeter standard is not suitable for mass flowmeters. 2. With such a low flow rate, not only is the pressure loss in the pipes small, but the pressure loss at the flow meter is also sufficiently low. When considering pressure loss, it’s not the diameter that matters but rather the flow rate; assuming the flow rate is close to 0, the pressure loss will be low regardless of the size of the pipe. 3. Some pipes are designed to be larger for the following reasons: the original design called for larger sizes, the need to make use of existing components, and requirements related to mechanical strength.