DN15 Vortex flowmeter

A vortex meter is a type of volumetric flow meter that makes use of a natural phenomenon that occurs when a liquid flows around a bluff object. Vortex flow meters operate under the principle of vortex shedding , where vortices (or eddies) are shed alternately downstream of the object. The frequency of  vortex shedding is directly proportional to the velocity of the liquid flowing through the meter.

Vortex flow meters are best suited for flow measurements where the introduction of moving parts presents problems. They are available in industrial grade, brass, or all plastic construction. Sensitivity to variations in process conditions is low and, with no moving parts, wear is relatively low compared to other types of flow meters.

Intelligent transmitters are also provided with diagnostic subroutines for signal components or other faults. Smart transmitters can initiate test routines to identify problems with both the meter and the application. These on-demand tests can also assist in ISO 9000 verification.
Some vortex flowmeters can detect mass flow. One such design measures both vortex frequency and vortex pulse strength simultaneously. From these readings, the density of the process fluid can be determined, and the calculated mass flow within 2% of the span.

The inaccuracy of most vortex meters is 0.5-1% of Reynolds numbers over 30,000. As Reynolds number decreases, metering error increases. At Reynolds numbers less than 10,000, the error can reach 10% of the actual flow.

When measuring multi-phase flow (solid particles in gas or liquid; gas bubbles in liquid; liquid droplets in gas), vortex meter accuracy will decrease due to the meter's inability to distinguish between phases. Wet, low-quality steam is one such application: the liquid phase should be uniformly dispersed within the steam, and vertical flow lines should be avoided to prevent slugging. When the pipe is horizontal, the liquid phase is likely to travel on the bottom of the pipe, so the inner area of the pipe should be kept open at the bottom. This can be achieved by installing the bluff body horizontally. Measurement inaccuracy in such applications is about 5% of the actual flow, but with good repeatability.