[A flow meter selection to solve problems is a challenging task. Therefore, when selecting you should in detail…]
Flow measurement is an important and challenging task. It is related to the fact that each individual technological process imposes different requirements to flow meters. For example, efficient operation of a vortex meter depends on the flow rate make it impossible to use them in low medium speed processes.
What do we need to know about flow meters?
In order to make optimal selection of the required flow meter type suitable for a particular process, you should know its operating principle and features. Next, let’s consider some of the flow meter types frequently used in industry.
Types of flow meters according to the principle of operation
Rotameters
The rotameter refers to mechanical devices, as there are moving parts in its design. The principle of operation includes the flow influence on two rotors located across. Their rotation is proportional to the flow rate. The meters record the number of rotations of the rotor and convert them to the volume value.
Such meters have a very simple design and are quite versatile in use. We should highlight some of their advantages as follows:
— Excellent metrological characteristics.
— No special installation requirements.
— Low cost.
One of the most popular applications of rotameters includes gas flow calculation.
Turbine flow meters
The main elements in the design of turbine flow meters include a flow straightener and a rotor with blades. The flow passing through the flow meter drives the rotor blades at a certain angular speed, which is fixed using a magnetic counter, for example. The rotation speed directly depends on the flow rate.
Turbine operating principle devices have high stability and accuracy of readings. The sensors also have excellent repeatability, which makes them a good solution for use in commercial metering systems.
Disadvantages of mechanical flow meters
The above types of meters relate to mechanical and contact ones, since the flow directly contacts and drives the measuring element. The disadvantages of such devices are as follows:
— Need for constant maintenance – the sensor design may become clogged and the bearings may fail.
— Pressure drop while the flow passing through the sensor structure.
— Sensor replacement requires stopping the technological process or the availability of bypass lines.
Next, consider flow meters without moving mechanisms in their design.
Vortex
The principle of a vortex flow meter operation is as follows: a special element (more often in the form of trapezoid) creates some obstacle to the flow, thereby creating vortices and then the sensor fixes frequency of vortex oscillations. A pressure gauge can act as a sensing element, fluctuations in the readings of which are connected with the flow intensity, and therefore the flow rate.
The advantages of vortex meters are:
— Absence of mechanical moving elements.
— Resistance to contamination.
— The operation capability with many environments.
— High measurement accuracy.
Among the disadvantages, it is worth noting the inability to work with low-speed flows and sensitivity to vibration.
Ultrasonic
Ultrasonic flow meters are non-contact devices that are installed outside the pipeline. Their principle of operation is based on difference in speeds of ultrasonic waves flowing along and against the current. The main design elements include a pair of ultrasonic sensors, which are located at an angle of 45° relative to the flow. One sensor sends a wave against the current, and the second one goes downstream. If we know the speed difference and pipeline parameters, the device electronics calculates the flow rate.
The ultrasonic flow meter is a contemporary and reliable solution for production. Its high cost, compared to simpler devices, is compensated for the following advantages:
— Easy pipeline installation does not require for stopping the technological process and other preparatory measures.
— High metrological characteristics.
— Reliability of measurements.
— Self-diagnosis functions. Contemporary devices have electronics that constantly check the operation of all the assembly units.
— Operation at high medium pressures.
— Measurement of flows at different speeds.
Conclusion
A flow meter selection to solve the problems, whether it is a control circuit or commercial metering, is a challenging task. Therefore, when selecting, you should familiarize yourself in detail with the features of the flow meters and correlate them with the conditions of your technological process. You may consult our specialists to simplify the flow meter selection process. They will answer all your questions and help you choose the optimal device model for your task.
