Every day, resource-saving technologies are being introduced into the gas industry more and more, which forces us to apply stringent requirements to gas metering systems. This automatically leads to stricter requirements for the flow measurement methods. High-quality flow meters must meet a number of requirements - reliability and accuracy of measurements, affordable price, high metrological characteristics.
Advantages and Disadvantages of Ultrasonic Measurement
Ultrasonic gas flow sensors have become widespread both in our country and abroad. Experts believe that the main advantages of the ultrasonic method for measuring flow are:
- Highest measurement accuracy.
- Extended dynamic range of measurements.
- Ability to operate without creating a differential pressure.
Most often, ultrasonic flow meters are used on medium and large pipelines. The devices are practically flawless, and they can only compete with the technology of variable differential pressure across the orifice device. This method is flawed for a number of reasons:
- The dynamic range is not wide enough.
- Significant resistance to fluid flow.
- Time-consuming and laborious dismantling of devices for regular calibration, which forces the process to be stopped.
Features of ultrasonic measurement
The principle of operation is based on the fact that an ultrasound pulse when directed along the gas flow propagates much faster than a similar pulse in the opposite direction. The difference between the transit time of a pulse is in direct proportion to the average velocity of the gas medium along the acoustic path.
The average flow rate, and, accordingly, the flow rate of the gas medium is measured by determining the transit time of the pulse in both directions. If you need to determine the speed with maximum accuracy, you can use several acoustic channels at once, with two transducers for each.
Despite its apparent simplicity and efficiency, ultrasonic measurement technology is not without its drawbacks. The main one is the inconvenient location of sensors that need to be installed at a certain angle to the pipeline. As a result, it is necessary to provide pockets for installing the converters. This causes contaminants to enter the sensitive area of the device, which not only reduces the measurement accuracy, but also eventually leads to device breakdown.
Innovative Ultrasonic Meter Design Techniques
According to the specialists of the company " Izmerkon " When preparing this material, some manufacturers have improved the ultrasonic method for measuring gas flow rate, which makes it possible to level the disadvantages of previously existing technologies. Here are some of the notable differences of the new method:
- Ultrasonic sensors are no longer placed at an angle, but perpendicular to the surface of the pipeline, which eliminates the need for a pocket for transducers.
- The outer emitting surface is well aligned with the inner surface of the measuring section.
- When working with two transducers, several measurement channels can be processed at once.
- The pulse detection system is able to provide the most accurate determination of the signal transit time in the forward and backward directions.
The new technique is based on the impulse method for determining the gas flow rate. Piezoelectric sensors are responsible for the excitation and reception of pulses, which are installed perpendicular to the surface of the measured pipeline. As the gas moves through the pipe, an ultrasonic wave is shifted, which affects the propagation time of the signal between the sensors.