Turbine Flow Meter Working Principle

A turbine flow meter unit is constructed of a multiple-bladed rotor installed with a pipe in a perpendicular direction to the fluid flow. As the liquid flows through the blades, the rotor rotates. The rotational speed of the rotor is correlated to the flow rate of the liquid. The speed of the rotor can be sensed by various mechanisms such as magnetic pick-up, photoelectric cell, or gears. A tachometer can also be attached to the turbine for measuring its rotational speed which in turn helps in determining the liquid flow rate. After proper installation, turbine meters offer good accuracy, mainly with low-viscosity liquids. Hence, turbine meters are widely employed in applications where accurate measurements are required. When a turbine flowmeter is calibrated and operated for a single fluid, constant conditions, its turndown ratio can go beyond 100:1. Moreover, accuracy of a turbine flowmeter can be as good as +/-0.1%. The major problem associated with the usage of turbine meters is bearing wear. To prevent this problem, a “bearingless” turbine meter design has been introduced recently. Various turbine flowmeter designs have been manufactured. However, they all operate on the same basic principle which says “If a fluid moves through a pipe and acts on the vanes of a turbine, the turbine will start to spin and rotate. The rate of spin is measured to calculate the flow”.

Turbine Flow Meter Application

Turbine flow meters are used to measure clean, dry gases and liquids such as hydrocarbons, chemicals, gases and vapors, fuels and other types of liquids with lower viscosity, and for applications requiring highly accurate and precise measurements.

These turbine flow meters are mostly used for military applications. They are also used in blending systems in the petroleum industry. They are effective in aerospace and airborne applications for energy fuel and cryogenic (liquid oxygen and nitrogen) flow measurements.

Typically, their applications are found across various industries such as petroleum, automotive, laboratory and water treatment. In some cases, applications are also found in the beverage and chemical industry as well.

A few examples of applications include:

  • Particle cleanliness testing
  • Water treatment
  • Monitoring input flow to an analyzer
  • Dispensing chemicals in a laboratory




TURBINE FLOW METER PARTS




Services:-

Relatively clean liquids, gases, and vapors (some units for gas service are also covered.

Sizes :-

3/16 to 24 in. (5 to 610 mm) in flow-through designs.

Outputs:-

Generally, linear frequency outputs are provided, but 4- to 20-mA DC can also be obtained through conversion.

Operating Pressure :-

1500 PSIG (10.3 MPa) in standard and 5000 PSIG (34.5 MPa) in special designs.

Pressure Drops:-

Usually, one velocity head or about 3 to 5 PSIG (20 to 35 kPa).

Operating Temperature :-

− 58 to 300 ° F ( − 50 to 150 ° C) in standard and − 328 to 840 ° F ( − 200 to 450 ° C) inextended pickup designs.





Materials of Construction :-

Normally, stainless-steel housing and rotor with tungsten carbide sleeve bearings are used, but Hastelloy  C or other housing materials and ceramic or PTFE bearings are also available.

Rangeability :-

10:1 unless limited by use of line-size units or by high process fluid viscosity.

 
Turbine flow meter price :-

Turbine flow meter with a preamp (but without readout electronics) and with150-lb carbon steel flanges can be estimated as follows (1 in. = 25.4 mm): 0.5 to1.5 in., $2200; 2 to 3 in., $2800; 4 in., $3500; 6 in., $5000; 8 in., $8000; 10 in.,$12,000; 12 in., $16,000; 16 in., $28,000; 18 in., $32,000; 20 in., $50,000; 24 in.,$75,000. Electronic readout devices might include auxiliary, explosion proof power supply, $1200; remote register drive, $3500; frequency-to-analog converter with digital display, $1200; locally mounted, explosion-proof totalizer /flow indicator, $1200. Accessories include flow straighteners, strainers, batch control units,and two-stage shutoff valves.



Turbine Flow Meter Advantages and Disadvantages

Turbine flow meter Advantage :-

  • Good accuracy
  • Excellent repeatability and range
  • Fairly low pressure drop.
  • Easy to install and maintain
  • Good temperature and pressure ratings
  • Can be compensated for viscosity variations





Disadvantage of turbine flow meter :-

  • High cost (expensive)
  • Limited use for slurry applications
  • Problems caused by non-lubricating fluids

Turbine flow meter Installation Procedure :

Before installation, the flow meter should be checked for foreign material and to ensure that the rotor spins freely. All upstream fluid lines should also be cleared of any debris. Also, make sure that fluid flow has been shut off and all pressure in the lines has been released prior to installing the flow meter into an existing system.


The flow meter must be installed with the flow direction arrow pointing in the direction of fluid flow. The flow direction arrow can be found on the side of the flow meter. The flow meter is designed to work in any orientation, but the preferred orientation is to have the meter installed in horizontal piping. The fluid to be measured is recommended to be filtered. The best location for the filter/strainer would be upstream of the flow meter, after any other system components, while maintaining straight piping requirements. The preferred plumbing setup is one containing a bypass line (figure 1). 

This allows meter inspection and repair without interrupting flow, as well as the ability
to cycle the fluid through the system filter before diverting to the flow meter. If a bypass line is not used, it is important that all flow control valves be located downstream of the flow meter (figure 2). For optimum flow meter performance a minimum length of upstream and downstream piping is required. It is recommended that a minimum length equal to 10 pipe diameters of straight pipe be installed directly on the upstream side of the flow meter and 5 pipe diameters on the downstream side of the flow meter. This helps to eliminate turbulence in the fluid. Having shorter pipe lengths, other system components and elbows to close to the flow meter may adversely affect the accuracy and repeatability of the flow meter. Piping should be the same size as the meter bore or port size.
Do not locate the flow meter or the connection cable close to electric motors, transformers, sparking devices, high voltage lines or place connecting cable in a conduit with wire supplying power for such devices. These devices can induce false signals in the flow meter coil or cable, causing the meter to read inaccurately

Turbine Flow Meter Calibration :

turbine meter consists of a practically friction-free rotor pivoted along the axis of the meter tube and designed in such a way that the rate of rotation of the rotor is proportional to the rate of flow of fluid through the meter. This rotational speed is sensed by means of an electric pick-off coil fitted to the outside of the meter housing. The only moving component in the meter is the rotor, and the only component subject to wear is the rotor bearing assembly. However, with careful choice of materials (e.g., tungsten carbide for bearings) the meter should be capable of operating for up to five years without failure. There are several characteristics of turbine flow meters that make them an excellent choice for some applications. The flow sensing element is very compact and light weight compared to various other technologies. This can be advantageous in applications where space is a premium

Primary Vs. Secondary Standards

A primary standard calibration is one that is based on measurements of natural physical parameters (i.e., mass, distance, and time). This calibration procedure assures the best possible precision error, and through traceability, minimizes bias or systematic error.
A secondary standard calibration is not based on natural, physical measurements. It often involves calibrating the user’s flow meter against another flow meter, known as a “master meter,” that has been calibrated itself on a primary standard.

Calibration

“To calibrate” means “to standardize (as a measuring instrument) by determining the deviation from a standard so as to determine the proper correction factors.” There are two key elements to this definition: determining the deviation from a standard, and ascertaining the proper correction factors.
Flow meters need periodic calibration. This can be done by using another calibrated meter as a reference or by using a known flow rate. Accuracy can vary over the range of the instrument and with temperature and specific weight changes in the fluid, which may all have to be taken into account.
Thus, the meter should be calibrated over temperature as well as range, so that the appropriate corrections can be made to the readings. A turbine meter should be calibrated at the same kinematic viscosity at which it will be operated in service. This is true for fluid states, liquid and gas.

Master Meter

A master meter is a flow meter that has been calibrated to a very high degree of accuracy. Types of flow meters used as master meters include turbine meters, positive displacement meters, venturi meters, and Coriolis meters.
The meter to be calibrated and the master meter are connected in series and are therefore subject to the same flow regime. To ensure consistent accurate calibration, the master meter itself must be subject to periodic re-calibration.

Gravimetric Method
This is the weight method, where the flow of liquid through the meter being calibrated is diverted into a vessel that can be weighed either continuously or after a predetermined time.
The weight is usually measured with the help of load cells. The weight of the liquid is then compared with the registered reading of the flow meter being calibrated.
Volumetric Method
In this technique, flow of liquid through the meter being calibrated is diverted into a tank of known volume. The time to displace the known volume is recorded to get the volumetric flow rate eg:- gallons per minute. This flow rate can then be compared to the turbine flow meter readings

K-Factor

“K” is a letter used to denote the pulses per gallon factor of a flow meter.
Repeatability
The maximum deviation from the corresponding data points taken from repeated tests under identical conditions.
Flow Transfer Standards
Unlike primary flow standards, whose most important characteristics are their traceability to primary physical measurements (resulting in the minimization of absolute uncertainties, with less concern for usability or cost issues), the key criteria for secondary Flow Transfer Standards are portability, low cost and the ability to calibrate the flow meter in the physical piping configuration it lives in.
Instead of removing flowmeters from service for re-calibration, FTS devices allow users to “bring the calibrator to the flow meter.” These portable, documenting field flow calibrators are intended for in-line calibration and validation of meters using the actual process conditions for gas or liquid.
Advanced FTS systems in corporate hand-held electronics with built-in signal conditioners, thus eliminating bulky interface boxes and the need to carry a laptop computer into the field. High-quality Flow Transfer Standards also have the capability of measuring and correcting the influences of line pressure and temperature effects on flow.
Operation of a portable Flow Transfer Standard requires that a master meter be installed in series with the flow meter under test. The readings from these instruments are compared at various flow rates or flow totals.
A technician can install the master meter in the same system as the test meter, perform the calibration, and note any changes in performance. New calibration data might cause re-scaling or new data points to be programmed into a flow meter’s computer to align the measurement with the current flow calibration data.

Typical Calibration Techniques

Most flow meter calibration service suppliers provide a choice of calibration techniques to accommodate different applications and flow measurement requirements. One of the most common techniques is the single-viscosity calibration, which consists of running 10 evenly spaced calibration points at a specified liquid viscosity.
Single-viscosity calibrations are recommended when the viscosity of the liquid being measured is constant. If a higher degree of accuracy is needed, again, the more data points taken the better defined the meter calibration curve will be.




Turbine flowmeter Manufacturer

Turbine Flow meter Manufacturers / VendorsCountryWebsitePhone No.
DANIELUKwww.daniel.com+44 1786433400
FAURE HERMANFRANCEwww.faureherman.com+33 169827700
BOPP & REUTHER MESSTECHNIK GMBHGERMANYwww.burmt.de+49 6232657508
FOXBOROGERMANYwww.foxboro-eckardt.com+49 7115020
EMERSONFRANCEwww.amm-marseille.com+33 491602263
EMERSONUKwww.frco.com+44 1162822822
OIL & GAS SYSTEM LIMITEDUKwww.ogsl.com+44 1353666640
OVAL CORPORATIONJAPANwww.oval.co.jp+81 333605121
SMITH METER (FMC)GERMANYwww.fmcmeasurementsolutions.com+49 41013040
SOLARTRON MOBREYUKwww.solartronmetrology.com+44 1243833333




3 thoughts on “Turbine Flow Meter Working Principle”

Leave a Comment

Your email address will not be published. Required fields are marked *