Non-Intrusive Flow Measurement with Ultrasonic Sensors – Important for EX Areas
EX areas are areas where an explosive atmosphere can potentially occur. This risk is particularly present where explosive substances such as powders or liquids are manufactured, processed, transported or stored. Especially in the chemical industry, with its often aggressive and toxic media, users, therefore, rely on non-intrusive measurement technology. New devices offer a high degree of flexibility with regard to media, aggregate states, pipe materials and dimensions, as well as pressure and temperature. The ‘clamp-on’ ultrasonic sensors used for this purpose are simply mounted on the outside of a pipe, usually even while the pipe is in operation. Flow measurement from the outside of the pipe means measuring from the safe side – without any wear caused by the medium, without any risk of leakage, and without any pressure loss and thus impairment of system availability.
Special Features of the EX Area
It is certainly a challenge to transport such advantages into potentially explosive atmospheres without having to make compromises in terms of measurement size and accuracy. For this purpose, current ultrasonic systems measure the flow according to the transit time difference method. From the difference in the transit time of ultrasonic signals that are radiated into the pipe with and against the direction of flow, the transducer calculates the average flow velocity of the medium and ultimately the volume flow. Inside the pressure-proof encapsulated housing, a powerful processor ensures the necessary measuring performance. The speedily measured value output (also directly into the IT system via Wi-Fi, for example) allows highly dynamic processes to be recorded in real time. Transducers and sensors are calibrated independently of each other in a patented process and without the influence of application-related disturbance variables. This ensures high measuring accuracy at all times – regardless of the combination in which the measuring system is used.
High Flexibility for Additional Applications
Such a ‘clamp-on’ device measures virtually anything that flows. In concrete terms, this means: The liquid metering devices are suitable for non-intrusive flow measurement of virtually all liquid media, from the thinnest pipe to the largest pipe – regardless of the pressure prevailing inside and over a wide temperature range. In conjunction with an appropriate sensor attachment for extreme temperatures, the flow of liquids can be measured non-intrusively in a temperature range from -190°C (for example, in the case of LNG) to over 600°C. The technology of the devices enables reliable flow measurement even of liquids with an increased solid or gas content.