Coriolis mass flow meter installation
Most manufacturers claim that their Coriolis flow meters are not adversely affected by installation effects. As such, they should not require large lengths of straight length pipe work upstream and/or downstream of the flow meter. However, compliance with the manufacturer’s guidance is necessary. This guidance can vary depending on flow tube design and Coriolis flow meter manufacturer.
Coriolis flow meters are not usually affected by swirling fluid or non-uniform velocity profiles resulting from upstream or downstream piping configurations. However, good practice should be observed at all times, by ensuring that the flow meter is installed with adequate upstream and downstream straight pipe work.
Although not overly affected by installation effects, Coriolis meters should not be installed close to valves that will regularly open and close as this can cause pulsations and vibrations in the flow. This has the potential to lead to significant mismeasurement of the mass flow.
Coriolis flow meters can be adversely affected by stress applied from the adjoining pipe work, and by vibrations acting on the flow meter. As such, manufacturers specify that their flow meter must be fixed firmly to the pipeline. To achieve this, the adjoining pipe work should be clamped securely both upstream and downstream of the flow meter.
Cavitation is a serious consideration and can occur in the process line if the system pressure drops below the vapour pressure of the fluid. To prevent this from occurring, the back pressure should be kept at a sufficient level. If the fluid is highly viscous or if the meter is smaller than the line size, the pressure drop across the Coriolis flow meter may be an issue.
The fluid pressure drop through the Coriolis flow meter is extremely important and is often the key parameter considered when sizing the device. To avoid a large pressure drop, some users select a Coriolis flow meter that has a larger bore than the line size. However, oversized meters are not only more expensive, they are also less accurate. This is because the flow rates will be at the lower end of the flow meter’s operating range, resulting in a higher flow measurement uncertainty.
Direct sunlight can adversely affect the flow meter’s measurements due to the effect the temperature can have on the flow tubes. An elevated temperature heats the flow tube and thus the stiffness of the tube changes due to the Young’s modulus. As such, most Coriolis manufacturers specify that their flow meter should be installed in a shady location, avoiding direct sunlight.
