Today, fluid flow measurement is one of the most important measurement parameters in various industries.
In fact, most experts, after measuring temperature, consider flow to be the most important quantity in industry.
Due to the importance of measuring this quantity as well as the variety of process processes in different industries, different methods for measuring fluid flow have emerged over time.
Choosing the right Flowmeter for any application requires general knowledge of various flowmetry methods and considering the main measurement parameters such as accuracy, cost, repair and calibration costs, compatibility of Flowmeter performance with the conditions of the production process.
Types of steam flowmeters
There are different types of flowmeters, the ones that are suitable for the use of steam and condensate are:
- Orifis Plate Flowmeter
- Flowmeter turbine
- Vertex flowmeter
- Ultrasonic flowmeter
Orifis Plate
The orifice plate is a circular smooth disk with a circular hole in its surface and a sharp edge to allow fluid to flow.
It also has a tab that says “Orifis Plate Specifications” .
This flowmeter measures the flow rate based on the pressure difference of the fluid passing through its orifice.
In a turbine flowmeter, the vane rotor hangs axially in the flow and rotates at a rate proportional to the fluid velocity.
In some models, the rotor blades are made of a magnetic material that induces alternating voltage in the signal pickup coil.
In other designs, the rotation speed is detected by a radio frequency pickup, with a high-frequency carrier signal modulated by the rotating blades.
Turbine flowmeters are very accurate in good condition, but they are fragile and costly to maintain.
Turbine meters are computational types that have been used since the 1960s and with the improvement of their technology, they have become more popular among companies.
These meters determine the mass flow rate of the blade by measuring the speed of each blade rotor that is floating inside the current.
The rotational speed of the rotor is proportional to the mass flow.
For petroleum products, the volumetric flow rate is equal to the product of the cross-sectional area of the flow and the speed of the rotor, in which the measurement coefficient is applied and temperature and pressure corrections are made.
The calculation method for natural gas is the same as above, with the only difference that the compressibility property must also be considered.
The performance of turbine meters is excellent in case the flow rate is uniform and the fluid properties are compatible (density and viscosity do not change).
In fact, these counters want a smooth and direct flow, and therefore a direct pipe is used before oil or natural gas enters these counters and also after leaving the flow.
If there is not enough space to install a straight pipe, smoothing blades (small pipes inside lines with larger diameters) are used.
These types of counters are used for LIQUID SERVICE and GAS SERVICE.
Advantages of a turbine flowmeter
- They are small in size and light in weight.
- They are very linear and reproducible.
- They are cheaper than other types of flowmeters.
- Due to the limited mechanical parts, they need a small number of repairs.
- They are one of the most reliable flowmeters with dual pulse output capability.
Disadvantages of turbine flowmeter
- They have a low operating range in high viscosity fluid operating services.
- Their performance is highly dependent on the viscosity of the fluid.
- They are only suitable for completely single-phase currents.
- They are highly dependent on the upstream profile.
Vertex flowmeters
The vortex flowmeter is based on a phenomenon in fluid dynamics discovered by a scientist named Theodore von Kármán.
In practice, the Vertex Flowmeter operates by a mechanism based on measuring the oscillations created behind a fluid barrier.
Vertex flowmeter is used in many industries to measure liquids, gases and vapors.
In the chemical and petrochemical industries, for example in power generation… in fluids such as saturated steam, very hot steam, compressed air, nitrogen, biphasic gases, flue gas, carbon dioxide, demineral water, solvents, heat transfer oil, boiler feed water And…. This flowmeter can be used.
Flow measurement in Vertex flowmeter is volumetric, but for mass measurement in cases such as steam, you must use a separate pressure transmitter as well as a temperature sensor and connect them to the flow computer to calculate the mass or amount of energy transferred.
Ultrasonic flowmeter
Ultrasonic Flowmeter Ultrasonic Flowmeter is now an integral part of most ultrasonic methods for measuring instrument, especially non-contact sample is sent.
In “ultrasonic flowmeters” which are used in a wide range of fluids, gases and liquids, according to the Doppler properties that you are familiar with in physics, a frequency is generated from one source and on the other hand, a receiver checks this frequency moment by moment. .
If the fluid flow changes, this reciprocating frequency will change significantly due to the fluid velocity.
Measuring and calibrating these changes in terms of flow will allow you to measure flow by ultrasonic method.
In practice, the flow measurement technique by ultrasonic method will have its complexities, but the basis for measuring most ultrasonic flowmeters is the Doppler mechanism.