Advances in flow metering technology mean more options for a broad spectrum of processes and flows. One such specialized technology is the vortex flow meter, an innovative flow measurement device capable of handling liquids, gases, steam, and corrosive applications. A large variety of industries can benefit from vortex technology. It is well-suited for any application where clogging or leaks occur, steam measurement is needed, or where Safety Instrumented Systems (SIS) are used. These flow meters have exceptional capabilities and benefits worth exploring, reducing inefficiencies and increasing safety in industries across the board.
The Technological Edge of Vortex Flow Meters
Vortex flow meters are composed of three main parts: a body, a sensor, and a transmitter. As the process flow moves through the body of the meter, an obstruction called a shedder bar forces the flow around it, creating vortices. An oscillating sensor measures these areas of alternating differential pressure. The frequency of this movement allows for the use of the von Kármán effect to calculate the volumetric flow rate.
This distinctive arrangement means that there are no moving parts within the meter to maintain or repair. Emerson’s unique design utilizes vortex technology with a non-wetted sensor, making on-line maintenance possible. In the rare occasion that the vortex sensor needs to be replaced, sensor replacement can be performed without breaking the process seal.
Vortex flow meters are easy to install without impulse lines and can withstand high process pressures and temperatures. They are used in a broad spectrum of processes because they have a wide turndown range. Emerson’s special non-clogging and non-leaking vortex flow meters mean improved sensor accuracy and safety, especially in hazardous chemical applications. They are also a two-wire device with low power consumption making them excellent choices for use in remote areas.
The Von Kármán Effect and Fluid Velocity
The von Kármán effect is what makes vortex technology possible. Named for the Hungarian physicist who studied the phenomenon more commonly known as a Kármán vortex street, the analysis is possible when flow is forced around a cylindrical object creating a destructive path of swirling vortices. When this turbulence occurs around buildings, airplanes, or other structures, the path of vortices can be calamitous. Fortunately, within a flow meter, they are beneficial for calculating a fluid’s velocity.
The velocity of the fluid is directly proportional to the frequency of the vortices generated by the shedder bar within the meter body. Flow rate (vol/sec) = Vortex Frequency (p/sec) / K-Factor (p/vol) where the K-factor is a calibration constant formed in a flow lab measured by the pulses generated divided by one unit of volumetric flow. This K-factor constant is accurate over a large operating range of flow patterns.
Wide Variety of Capabilities and Improvements
An adequate ratio of inertial forces to viscous forces must exist in the process flow to create and measure vortices within the flow meter body. With certain low flow applications, this could mean vortex technology isn’t the right fit. However, a reducer configuration can fix the issue for some applications. A reducer decreases the cross-sectional area of the meter body by one line size, forcing the process flow through the pipe at a high enough velocity to create the required vortices. Emerson’s reducer vortex flow meters use the same face-to-face dimensions as standard flanged vortex meters. This practical design eliminates the need for field-installed piping reductions, cutting costs and avoiding the risk of installation.
Vortex flow meters can comfortably accommodate Safety Instrumented Systems (SIS) applications as well. Dual and quad vortex flow meters provide a simple way to institute redundant, independent sensors and electronics. These configurations verify flow meter data, establishing redundancy for uncommon modes of failures and protecting against the spurious trips SIS plants may experience.
The versatility of vortex technology makes these flow meters an excellent choice for countless process applications. Emerson’s all-welded, all-cast vortex models are available in a variety of body configurations and multi-variable capabilities. Contact the flow measurement specialists at Emerson to find out if a vortex flow meter is right for your process.
