By Steve Pagano
The swirl flowmeter advances vortex flow technology by improving accuracy, simplifying installation, increasing turndown, and reducing cost of ownership. Over the last 30 years, vortex flowmeters have become standard fixtures for many industrial process applications, especially for measurement of gas and steam flowrates. Swirl meters operate on similar principles, but have certain advantages.
- Swirl meters create their own flow profile within the meter, so they require only three straight pipe diameters upstream and one downstream. Vortex meters typically require a minimum of 15 diameters upstream and five downstream to develop a proper flow profile for accurate measurements. So the swirl flowmeter better fits applications with tight piping requirements.
- When applying vortex meters, the user typically chooses a flowmeter reduced by one or two pipe sizes from the process pipeline size. This ensures that the flowmeter experiences the higher velocities required across the desired flow range, but adds piping reduction and expansion costs. Swirl meters require lower flow velocities for proper operation, and so usually may be sized the same as the process pipe size.
- Swirl meters have a turndown ration of up to 30:1, while most vortex meters are limited to 20:1 turndown ratios. Additionally swirl meters can perform to viscosities of up to 30 cp while vortex meters are generally limited to 8-10 cp maximum.
- Swirl meters offer a higher degree of accuracy, up to 0.5% better than most vortex meters in gas applications.
For these reasons, swirl flowmeters have been gaining ground on vortex flowmeters and are currently experiencing double-digit growth.