Exact Dual Rotor Advantages

The Exact™ Dual Rotor (DR) design extends the turbine flowmeter’s lower flow range far below traditional single rotor designs by overcoming the drag and torsional forces on the rotor. The dual rotors become hydraulically coupled, due to their counter-rotational direction. The angular flow path, onto the second rotor, overcomes the inertia due to its perpendicular force on the helical blades.

Three major physical benefits result from dual-rotor technology:

1. The ability to monitor the integrity of the bearing by looking at the frequency ratios of the both rotors.

2. The dual rotor significantly reduces flow swirl effects, eliminating the need for flow straighteners.

3. Developing of multiple viscosity calibrations or UVC plots blend over a wider flow range, yielding 60:1 usable flow ranges.

About the Technology

Turbine flow meters have traditionally had a repeatable flow range of approximately 100:1 and a maximum linear flow range of 30:1. These turndown numbers have always been a result of the single-rotor turbine meter becoming affected by blade drag at lower flow rates. This blade drag causes the turbine blade to stop spinning due to its’ inability to overcome the torsional forces at work.

Exact Flow’s patented dual-rotor turbine design extends the lower flow range far below what has been possible before. As fluid passes through the meter, the dual rotors become hydraulically coupled due to their counter-rotation. This allows the rotors to overcome the inertia and drag that affects all single-rotor turbine flow meters.

Exact Flow dual-rotor turbine flowmeters have an incredible repeatable flow range of up to as much as 500:1 and a UVC turndown range of 60:1. This allows the user to deploy fewer flow meters to cover a wide range of flow. This lowers the initial purchase cost, as well as simplifying system integration and future maintenance.

Dual Rotor Turndown Ranges

Advantages of Helical Rotors

Additional Exact Flow benefits are found in the use of helical rotors. Helical rotors are designed to minimize the resistance to flow, while imparting flow energy to the blades evenly. In other words, the energy transfer is optimized over the entire surface of the blade, rather than at only one specific point.

Helical rotors produce less pressure drop across the flow meter, as compared with the traditional flat-bladed rotor design. This reduction, translated into force, also reduces bearing wear resulting in maintaining the original calibration over a longer period of time. This makes the helical rotor ideal for providing the best value over the life of the meter.