Vortex meters


Thread Starter

Martin Sneesby

What really happens when the flow rate drops below the low flow threshold of a vortex meter?
Does the meter fail to detect low (laminar) flows so that the instrument output falls to zero before the flow stops, or do you continue to get some kind of signal with less accuracy until the flow stops completely? Can you get occassional, random readings from a vortex meter with no flow from vibration in the system?
The sensor output (not the meter's, remember) will continue to produce pulses but their accuracy and duration becomes less and less valuable, so the internal firmware of the transmitter is designed to produce a "low flow
cutoff" and gracefully drop the flow to zero in most systems I've seen.

Walt Boyes
From my experience there is a flow measurement below the recommended low threshold, it is just not empirically accurate. The vortex meters I have
used, do, however, seem to have a fairly good repeatability accuracy outside of the thresholds.

The vortex meter should have, and be calibrated, to ignore the lower level ambient vibrations. If there is outside interference that the meters
internal dampers can't eliminate, then mechanical isolation may help.

Bob Pawley

William L. Mostia, Jr

It is my understanding that at some point that there is not enough energy in the flow stream to generate detectable, consistent vortexes. If you were to look at the signal below the vendor stated limits, you may still see some vortexes but the vendor will choose a safe cutoff value to provide consistent and accurate measurement for the range of applications that they anticipate.

Bill Mostia
William(Bill) L. Mostia, Jr. PE
Principal Engineer
WLM Engineering Co
Independent I&E Consultant
P.O. Box 1129
Kemah, TX 77565 USA
E-Mail: [email protected]

These opinions are my own and are offered on the basis of Caveat Emptor.