Turbine flowmeters for liquids

Calibrated flow measurements with a turbine flow meter

The turbine flow meter is particularly suitable for custody transfer measurements, especially for low-viscosity fluids. The instrument gives a quantity of pulses per unit volume with a linearity of < 0.15 %. Another very important reason is that a turbine flow meter can be put in series with a prover (also called master meter) in the measuring installation. This allows the measured value to be verified.

Low viscosity fluids

The most important component in a turbine flowmeter is the turbine (or also called rotor). For low-viscosity fluids, a "classic" turbine can be chosen, with multiple flat blades (more than 6) welded to the shaft. In this way an attempt is made to optimally transfer the fluid speed to the rotating rotor, while keeping the pressure drop over the instrument low. This is a very good solution for this kind of liquids.

High-viscosity liquids

For liquids with a higher viscosity, one often chooses a turbine with 2 or a maximum of 4 blades with a slightly curved shape: helical blade rotors. These are made of a single piece of rod material and have the characteristic that the friction with the fluid at each part of the turbine is minimal. This makes a turbine flow meter suitable for use with higher viscosity and a PD meter, which is usually more expensive and has a higher pressure drop, is not necessary.

Applicability of a turbine flow meter

Turbine flowmeters are extremely accurate but for a large number of process applications other measurement techniques are better. A limitation of the turbine flowmeter are the moving parts that lead to the need for maintenance while there are also alternative measurement techniques without these moving parts. Besides that rather high OPEX they are sometimes the more expensive choice in purchase and they do not have a full flow. But if accuracy and repeatability is priority number 1, then nothing beats a turbine flowmeter. It's not for nothing that many calibration labs have a turbine flowmeter as their master meter.