Which Flowmeter to Choose for Vane Pump Operations?

Related Vendors

Lutz Pumpen GmbH

Maag Pump Systems AG

Anton Paar GmbH

Blackmer

Engineers found it difficult to get rid of air in one meter, which had intentionally been mounted horizontally in the test rig. The manufacturer recommended installing the meter vertically and this was shown to be correct. Air in the meter creates turbulence and reduces both the accuracy and the stability of the density measurement. However, even when installed horizontally, flowrates of about ten percent of the maximum rated flow successfully removed air in less than one minute.

When mounted vertically, air was eliminated from the meters at less than 1 % of maximum rated flow. Alternatively, a valve can be used to throttle the outlet to increase pressure, allowing trapped air to dissolve in the test fluid.

Interference Between Pumps an d Flow Measurements

To address the specific question of interference between pressure pulses from the sliding-vane pump and the Coriolis flowmeter, a variety of pumps with different vane frequencies were tested. High-speed pressure and flow data was collected, and minimum and maximum pressures and flows recorded. The results indicated that there was no correlation between the vane frequency, pressure pulsing and measured flow at the meter.

Blackmer’s engineers attempted to operate the sliding-vane pumps at speeds where the pressure-pulse frequencies would be at the same resonant frequencies as the Coriolis flowmeters themselves. They then varied the speeds to levels (pressure-pulse frequencies) above and below the meter’s published natural frequency.

The engineers could not induce any constructive or destructive interference into the vibrating Coriolis tubes by intentionally operating them in the natural frequency range of the tube spring/mass system. Nothing they could do within the normal operation of the pumps caused any degradation of meter accuracy.

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