What is a turbine flowmeter?
In this article, we will discuss a very common flow measuring device called a turbine flowmeter. Depending on who you are talking to, a turbine flowmeter has one or two main parts. Some tell you that a turbine flowmeter has only one part: the mechanical component. Others consider the turbine flowmeter to have two parts: mechanical component and electrical component.
In this article, we will consider the turbine as a 2-part device. How does a turbine flowmeter work? First of all, let’s talk about how a turbine flowmeter works. A turbine flowmeter is placed directly in the flow path in a pipe. The mechanical part of the turbine flowmeter has a turbine rotor located in the current flow path. The only moving part of the turbine flowmeter is the mechanical rotor. The rotation speed of the rotor depends on the flow speed. Rotor blades are usually made of stainless steel. As the rotor rotates, each rotor blade passes through a pickup point, generating an electrical pulse. Depending on the type of rotor blades and the characteristics of the pickup unit, electrical pulses are generated in different ways.
Magnetic pickup sensor
In most turbine flow meters, magnets are mounted on the blades and a magnetic pickup sensor is used to generate pulses. The faster the current, the faster the rotor rotates and the greater the number of pulses.
The shape and voltage level of the pulses produced depends entirely on the type of pickup unit used.
1) The electric pickup device can be a simple 2-wire passive magnetic pickup that produces an AC output.
2) The electric pickup meter can be an active 3-wire device such as the Hall Effect sensor that produces cleaner and more uniform square wave pulses.
As mentioned earlier, the turbine rotor rotates at different speeds depending on the fluid flow rate. Fluid Velocity is the measurement of the distance that a particle of matter travels per unit time. Normal speed units are feet per second or meters per second. Fluid Velocity plays a very important role in the operation of the turbine flow meter, but in most applications, a turbine flow meter is used to measure the volume flow.
Volumeetric Flowrate represents the volume of fluid that passes through a point in a single unit. If you can count the number of gallons of liquid passing through a given point in one minute, you can express volumetric flow.
Volumetric flow is expressed in units:
Gallons per minute (GPM) – cubic meters per second (cubic meters per second)
– Cubic feet per second (ft³ / s)
What is the K-Factor?
So now that we’ve looked at fluid velocity and flow rate, let’s talk about how to use a turbine flowmeter to measure volume flow. When purchasing a turbine flowmeter, it must be entered with a label or calibration certificate stating its K-Factor. This K-Factor is specific to each turbine flowmeter and is determined by the manufacturer. As discussed earlier, the turbine flowmeter produces a pulse, and the pulse rate depends on the speed of the liquid. The unique K-Factor announces the number of pulses generated for each unit of product through which it is generated. The K-Factor is expressed in terms of the number of pulses produced as 150 pulses per gallon.
Turbine flowmeter frequency
Suppose we use a turbine flowmeter to measure flow in gallons per minute (GPM). This turbine flowmeter has a coefficient of K 3 pulses per gallon. Remember that the unit of measurement is the frequency of hertz. 1 Hz equals 1 cycle per second. According to this point, we say that the turbine flowmeter produces a pulse frequency per second, which we express in hertz. If we have K-Factor 3 pulses per gallon, the output frequency in the volume flow rate of 200 gallons per minute (GPM) is 10 Hz or 10 pulses per second. If you are wondering where we got these values from, we have put a very useful K-Factor calculator to use.
We can connect the turbine flowmeter to a PLC frequency input card. The input frequency now shows the volume flow. In case of troubleshooting or ring calibration, we can use a variable frequency calibrator to simulate a turbine flowmeter.
Ordinary field control loop
Here is an example of a Turbine Volumetric Flowrate. A 2-wire passive sensor pickup unit generates pulses such as AC, which are conditioned by an amplifier before being sent to a high-count PLC input module.
Installing a turbine flowmeter
A typical installation requires 10 times the diameter of the pipe above the straight pipe and 5 times the diameter of the pipe downstream.
The turbine flowmeter can only be used in clean and lubricating liquids because suspended particles can easily damage the device. The turbine rotor must be located in the exact center of the flow, and slow flow is very important, often requiring smooth blades.
Negative points of using a turbine flowmeter
Even though they are one of the most accurate flow meters used today, they have their drawbacks.
1) The K-Factor is not always compatible with the entire flow velocity measurement range. Turbine flowmeters are not accurate at very low flow rates.
2) Viscosity is an issue because high or low viscosity liquids can change the rotor speed and affect the flowmeter calibration. Keep in mind that the K-Factor flow turbine is set at the factory using a specific set of parameters.
3) Not recommended for steam. Like other mechanical devices, rotor bearings wear out .
Where is a turbine flowmeter used?
In what industries is a turbine flowmeter used? Given their popularity, is it better to know in which industries turbine flowmeters are not used? You can find turbine flowmeters in oil and gas including distillation, water and wastewater, chemicals, energy, food and beverage, aerospace, pharmaceuticals and paper and paper.
A turbine flowmeter is placed directly in the flow path in a pipe and has a turbine rotor in the flow path.
– The faster the flow
The rotor rotates faster and the number of pulses generated by an electric pickup increases.
– In most applications, a turbine flowmeter is used to measure volumetric flow.
Each meter of turbine flow has a unique K-Factor that expresses the number of pulses generated for each unit of product that passes through it.
There are several important issues to consider when installing a turbine flow meter.
– Due to their popularity, there are very few industries that do not use turbine flow meters.
For more information on other articles on the site or in case of any questions or ambiguities, contact the industry’s industry experts .
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