Industry first: In-line flowmeter employs SAW-based technology

Developed in association with Coburg University in Germany, the SAW technology based flowmeter was created to offer a flow-metering solution to cover the largest possible measurement range and to measure reliably throughout its life. The result was a lightweight and compact solution that can be easily installed into a pipe without the need for any additional support. 

The technology sees surface acoustic waves being excited on the flowmeter measuring tube surface by a piezo-electric interdigital transducer which also sends waves through the measured fluid. In combination with the temporal curves, the reception signal characteristics create an acoustic fingerprint of the medium. From this the flow rate, density and temperature can be determined, as well as additional information about the medium itself. Importantly, because the procedure requires no elements to protrude into the medium, flow resistance remains unchanged. 

“During development of FLOWave, we identified that one of the biggest customer desires for a ‘perfect’ flowmeter was to have no sensing elements in contact with the medium being measured,” said Volker Erbe, product manager for sensors at Bürkert. “The SAW-based sensing component forms a fixed part of the measuring tube, so no probes are required in the flow.”

The FLOWave transmitter, sensor and measuring tube fulfil the most stringent hygienic requirements as the inside of the flowmeter tube can be manufactured to the same surface quality as the pipeline to which it is attached.

In addition to the volume flow rate, it is also possible to measure temperature and density, which allows calculation of the mass flow rate. FLOWave can detect fast changes in the flow rate and is therefore also suitable for high filling speeds. Interferences from system vibrations are ruled out due to the high excitation frequency of > 1 MHz. It is also unaffected by magnetic and electric forces. 

Effects such as those that occur as a result of gas bubbles or solids contained in fluids are less prominent with SAW technology and can be detected reliably. SAW technology is also said to be the only measuring procedure that is able to differentiate between laminar and turbulent flows.

John van Loon, global hygienic segment manager for Bürkert discussed some potential application areas. “Our first target market for FLOWave is water measurement in pharmaceutical applications. A great deal of low-conductivity water is used in this sector and flowmeters are needed to calculate water usage – where it is used as both an ingredient and for cleaning purposes. Customers are looking for optimum cleanability and process flexibility.” 

As with all flowmeter technologies FLOWave does also have some limitations. Erbe explained. “The technology is not suitable for use with gas or steam mediums, and is not suited to use on fluids at temperatures of 200°C, or at pressures of over 100 bar. 

The FLOWave range has also been one of the first products to benefit from Bürkert’s Efficient Device Integration Platform (EDIP) developed by the company to open the door to Industry 4.0 for its product range. It allows the devices to be combined into a single system and will make it possible to operate and monitor multiple Bürkert devices from a single display, and to run independent control functions or to access integrated web servers via Wifi and integrating into other networks, via gateway modules.

“Our goal when developing EDIP was to optimise the handling of devices in an integrated system, in addition to the development of new production functionality,” concluded Erbe. “It helps to fulfil our philosophy to work efficiently –from the product development stage. For the end user it will offer new functionality such as the ability to quickly retrofit and integrate new devices into a system during operation. It standardises communication data and is transparent to the complete factory, in line with Industry 4.0 requirements.”