In this video,
we’re going to discuss a very common flow measuring device
called a Turbine Flow Meter.
Depending on who you talk to,
a Turbine Meter has one or two major parts.
Some will tell you that the Turbine Meter has only one part:
the Mechanical component.
Others will refer to a Turbine Meter as having 2 parts:
The Mechanical component and the Electrical component.
In this video,
we’ll consider the Turbine Flow Meter
as a 2 part device.
Alright…let’s go.
First of all, let’s talk about how a Turbine Flow Meter works.
A Turbine Flow Meter is inserted in a pipe directly in the flow path.
The mechanical part of the Turbine Flow Meter
has a turbine rotor placed in the path of a flowing stream.
The only moving part of the Turbine Meter is the mechanical rotor.
The rotational speed of the rotor depends upon the flow velocity.
The rotor blades are usually made of stainless steel.
As the rotor spins,
the passage of each rotor blade past a pickup point
will generate an electrical pulse.
The electrical pulses are created in different ways
depending upon the rotor blades themselves
and the pickup unit characteristics.
In most Turbine Flow Meters, magnets are fitted to the blades,
and a magnetic pickup sensor is used to create the pulses.
The higher the rate of flow,
the faster the rotor turns and the greater the number of pulses.
The shape and the voltage level of the generated pulses
depend entirely upon the type of pickup unit used.
The electrical pickup sensing devices
could be a simple 2 wire passive magnetic pickup
producing an AC type output.
The electrical pickup sensing device could be a 3 wire active device
such as a Hall Effect sensor
that produces cleaner and more uniform square wave pulses.
As we said earlier,
the turbine rotor will turn at a different speed
depending upon the fluid flow velocity.
Fluid Velocity is a measurement of the distance
a particle of a substance traveled per unit of time.
Typical velocity units are feet per second
or meters per second.
Fluid Velocity plays a very important role
in the operation of a Turbine Flow Meter,
but in most applications,
a Turbine Flow Meter is used to measure Volumetric Flowrate.
Volumetric Flowrate indicates the volume of fluid
that passes a point in a unit period of time.
If you could count the number of gallons of liquid
flowing past a certain point in one minute,
you would be able to state the Volumetric Flowrate.
Volumetric Flowrate is expressed in units such as:
gallons per minute or GPM
cubic meters per second,
and cubic feet per second
OK…so now we've reviewed Fluid Velocity and Volumetric Flowrate,
let’s talk about how a Turbine Flow Meter is useds
to measure Volumetric Flowrate.
When you buy a Turbine Flow Meter
it should arrive with a tag or a calibration certificate
declaring its K-Factor.
This K-Factor is unique to each and every Turbine Flow Meter
and is determined by the manufacturer.
As we discussed earlier, the Turbine Flow Meter will generate pulses
and the pulse rate depends upon the fluid velocity.
The unique K-Factor declares the number of pulses
that will be generated for every unit of product passing through it.
K-Factor will be expressed in terms of the number of pulses produced
such as 150 pulses per gallon.
Let’s assume we are using a Turbine Flow Meter
to measure flow in gallons per minute or GPM.
This Turbine Flow Meter has a K-factor of 3 pulses per gallon.
Recall that the unit for Frequency measurement is Hertz.
1 Hertz is equal to 1 cycle per second.
With that in mind,
we say that the Turbine Flow Meter
produces a frequency of pulses per second
which we express as Hertz.
If we have a K-Factor of 3 pulses per gallon,
the output frequency at a Volumetric Flowrate of 200 gallons per minute or GPM
is 10 Hertz or 10 pulses per second.
If you are wondering where we derived these values,
we’ve included a very handy K-Factor Calculator for you to use.
You can find the link to this K-Factor Calculator file in the video description.
We can connect the Turbine Flow Meter to a PLC Frequency input card.
The input frequency now represents the Volumetric Flowrate.
If we are troubleshooting or performing loop calibration,
we can use a Calibrator with a variable frequency output
to simulate the Turbine Flow Meter.
Here’s an example of a Turbine Volumetric Flowrate measurement loop.
A 2 wire passive sensor pickup unit produces AC like pulses
which are conditioned by an amplifier
before being sent to a High Speed Counter PLC input module.
Typical installation requires 10 pipe diameters upstream of straight pipe
and 5 pipe diameters downstream.
The Turbine Meter can only be used in clean, lubricating fluid
because suspended particles can easily damage the device.
The turbine rotor must be positioned in the exact center of the flow
and laminar flow is critical often requiring straightening vanes.
Even though they are one of the most accurate Volumetric Flow Meters in use today,
they do have some downsides.
The K-Factor is not always consistent across the entire flow rate measurement range.
Turbine Flow Meters are not accurate at very low flow rates.
Viscosity is an issue
as thicker or thinner fluids can change the rotor speed
and affect the meter’s calibration.
Keep in mind that the Turbine Flow Meter K-Factors
was determined at the factory
using a specific set of parameters.
They are not recommended for steam.
As with other mechanical devices,
the rotor bearings wear out.
In What industries are Turbine Flow Meters used?
Considering their popularity,
a better question might be
in “What industries are Turbine Flow Meters not used”?
You will find Turbine Flow Meters in oil and gas including fracking,
water and wastewater, chemical, power, food and beverage,
aerospace, pharmaceutical, and pulp and paper.
If you want to learn more, you might want to review 3 of our other videos
“How Flow Meters Work”,
“what is Sensor Calibration and Why is it important”,
and “What are 2 wire and 4 wire Transmitter Output Loops?”
you can find the links to these videos in the description.
OK…let’s review:
A Turbine Flow Meter is inserted in a pipe directly in the flow path
and has a turbine rotor placed in the path of a flowing stream.
The higher the rate of flow, the faster the rotor turns
and the greater number of pulses generated by an electrical pickup.
In most applications,
a Turbine Flow Meter is used to measure Volumetric Flowrate.
Every Turbine Flow Meter has a unique K-Factor
stating the number of pulses
that will be generated for every unit of product passing through it.
There are several important issues to consider
when installing a Turbine Flow Meter.
Considering their popularity,
there are very few industries where Turbine Flow Meters are not used.
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