The order issue of pressure gauges and flow meters
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The process flow diagram of our factory shows that there are both pressure gauges and electromagnetic flowmeters on the pipeline where the outputs of the two pumps meet. Someone asked me today whether the order in which they are installed affects the measurement results. I really don’t know, so I’m asking those who are more experienced – is it necessary for the pressure gauge to be placed first and the flowmeter second? Thank you!
There shouldn’t be any special requirements, I guess.
Theoretically, vibration has a significant impact on the accuracy of electromagnetic flowmeters; therefore, it is better for the flowmeter to be as far away from the pump as possible； The flow meter itself requires a measurement section, namely 20D upstream and 10D downstream. If the pressure gauge is used to measure the pressure at the pump’s outlet, it is better for the gauge to be as close to the pump as possible.
Pressure gauges are usually installed at the pump outlet, located near the pump inlet, with check valves and gate valves connected in sequence； The flow meter should be placed after the valve, as flow meters require straight pipe sections before and after them.
A pressure gauge only measures static pressure, and there are no requirements regarding convection. So I don’t think it has any impact.
The pressure gauge should be placed at the pump outlet, and no fittings should be installed in the straight sections before and after the flow meter
It is better to have the pressure gauge in front and the flow meter behind. The pressure gauge is used to measure the pressure at the pump outlet; due to pressure drops in the pipes, the measurement point should be as close as possible to the pump for more accurate readings. Therefore, the pressure gauge is usually connected before the check valve； A flow meter measures flow rate, and the distance from the pump outlet does not matter; however, it usually requires straight pipe sections of about 10DN in length before and after it. Therefore, the flow meter is typically connected after the outlet check valve and globe valve ； So, it is due to their respective operational characteristics – one in front and the other behind – whereas the order of the two instruments itself doesn’t matter.
Place the electromagnetic flowmeter away from the pump to prevent vibrations from affecting the measurement. At the same time, whether the pressure gauge is located at the front or at the back, it should be outside the installation range of the flow meter
A pressure gauge is used to measure the outlet pressure of the pump. All factors located near the pump, such as flow rate and pressure, can affect the accuracy of flow measurement; therefore, a certain distance should be maintained from the pump outlet
It doesn’t matter whether the electromagnetic flowmeter or the pressure gauge is placed first or second; however, the length of the straight sections before and after the flowmeter must be ensured to meet the measurement requirements. Additionally, the electromagnetic flowmeter needs to be grounded and protected from vibrations.
Typically, the pressure gauge is installed at the pump outlet, thus being close to the pump, while the flow meter is placed as far away from the pump as possible to ensure accurate measurement and to minimize the impact of pump vibrations on it.