Vortex Flow Meters: Technology Driven by Turbulence

How they work, where they excel, advantages and limitations.

How they Work:

Vortex flow meters work by placing a strategic obstruction in the path of the flowing media. This obstruction is commonly called a bluff body. As the gas or liquid passes by, vortices are created. They form on either side and break away in an alternating pattern.

A good example of this type of behavior in everyday life is a flag that is attached to a flagpole. As the flowing wind contacts the flagpole, the flagpole itself creates the obstruction that causes the flag to billow in the wind in an alternating wave. Another example is a rock in the middle of a river. It is plain to see, via the eddy behind the rock and the subsequent flow, that there are vortices being created by the rock.

In the formed vortices, pressure decreases when a vortex is formed and increases when it is shed. This is true on both sides of the bluff body and causes pressure pulsations. The frequency of the pressure pulsations is directly proportional to the flow rate. A sensing element picks up the shifts from side to side behind the bluff body, amplifies the signal, and converts it to a 4-20 mA signal.

Vortex Principle of Operation

Advantages:

• Versatile: for gas, liquid, or steam
• Low to medium initial set-up cost
• Minimal maintenance in clean flow
• Reliable and accurate
• Longevity of service: no moving parts
• Can be installed at many angles as long as bluff body is submerged
• Unaffected by temp, pressure, density, or viscosity of the media
• Do not require impulse line heat tracing like orifice meters do

Common Applications:

• Food and beverage
• Chemical and petrochemical
• Energy industries
• Medical research
• Metallurgy
• Pharmaceuticals
• Oil and fuel

Considerations:

• Insertion types are available for large pipes
• Insertion types with optional extraction devices don’t require process shut down to remove them
• Multi-variable models can include temperature and pressure measurement
• Multi-variable models can show mass flow

Limitations:

• Low to medium pressure loss
• Not for high viscosity media or slurries
• Not for media that coats
• Strainers/filters may be required
• Not great accuracy for really high or really low velocity flows
• Not for pulsating flow
• Straight pipe requirements can be high
• Does not operate well with vibrations
• Not generally for batching applications

Sample Media:

• Water, chilled and hot
• Ultra-pure water
• De-ionized water
• Glycol mixtures
• Solvents
• Acids