In a conventional vortex flowmeter, a shedder bar separates the fluid flow, causing vortices with high- and low-pressure pulses at a frequency proportional to fluid velocity. Pressure sensors measure the pulse frequency, and electronics calculate volume and mass flow.
"Swirl is a little different twist," says Steve Pagano, senior product manager for ABB's vortex, swirl and Dp flow metering within the United States. "Instead of a shedder bar, a swirler at the meter entry puts the fluid into rotation. The flow delaminates into high- and low-pressure pulses, which are measured much like a vortex meter." But the swirl meter offers significant advantages.
First, the swirl meter reduces upstream and downstream straight piping requirements from the typical 15 to 50 pipe diameters needed for vortex technology. "The specially designed entry of the swirl meter profiles the flow like a built-in flow conditioner, reducing the upstream piping to a minimal three to five diameters," Pagano says.
Second, the swirl meter is accurate to lower flows at the bottom end of the range. "Where vortex drops off at about 20:1 turndown, swirl is accurate at 35:1 or 40:1," Pagano says. "This significantly changes the turndown ratio we can put the meter into and catch lower flows. For example, nighttime steam flows can be below measurability for vortex and still be caught by swirl."
Third, in order to have enough velocity, vortex meters often must be sized one or two sizes smaller than the pipe. Pagano notes, "Swirl meters can be the same diameter as the pipe run, eliminating the cost and space of reducing cones, and in some cases offer a lower pressure drop than the selected vortex, resulting in an energy savings."
ABB's new SwirlMaster flowmeters replace its TRIO-WIRL series to measure volume, mass and energy flow in a single device. The new SwirlMaster comes as standard (FSS430) or as an extended version (FSS450).
The FSS450 version features functions that are normally found in flow computers, such as steam-power calculation (with and without condensation return) and the ability to receive signals from other transmitters for density, temperature and pressure via 4-20 mA. The standard FSS430 omits the flow computer algorithms, but provides an analog output with HART communication. Both models feature ABB's universal graphical display (HMI), digital outputs configurable as pulse, contact and frequency output, and an optional integrated temperature sensor.
The SwirlMaster introduction is accompanied by a new VortexMaster series that follows the same philosophy with a lower-cost entry-level version (FSV430) for simple applications and an extended version (FSV450) that offers the same functions as SwirlMaster FSS450. "The simple and robust designs feature no moving mechanical parts and high accuracy with +/-0.50% of rate for the SwirlMaster and +/-0.65% (liquid) or +/-0.9% of rate (gas) for the VortexMaster," says Pagano.
The new devices have significantly improved sensor response time. The reaction time for a change in flow rate is reduced from three to six seconds to less than one second. At the same time, the measuring ranges have been extended (depending on the diameter of the device), in some cases significantly.
Advanced diagnostic and verification functions monitor device health through regular self-checks on the flow and temperature sensor, data storage and electronics. Diagnostic status messages are in accordance with the NAMUR directive NE107.
Both series have a piezo sensor with multiple elements to register the measured signals as well as pipe vibrations, which are used for compensation. The sensor, transmitter and general setup for both device series are identical for easy commissioning and spare part management. Pagano says, "A single set of electronics and one sensor cover the entire range, making this a very frugal meter from a maintenance standpoint."
The meters meet further NAMUR requirements including NE21 for electromagnetic compatibility (EMC) and NE43 for current output and contact outputs. Explosion-proof design and stainless steel housings are optional, as well as a remote design with a cable length of up to 30 m (100 ft.).
"A swirl meter might cost 10 to 15% more than a vortex meter, but has a lower installation cost, uses less real estate and offers higher performance," says Pagano. "Its five-year cost is less than a vortex meter and with lower maintenance, much less than using turbine meters. In applications where a turbine meter wears out in six months, a swirl meter lasts five to 10 years, with no maintenance."
For more information, see www.abb.com/measurement.