SAW technology for Bürkert flowmeter

This review of Surface Acoustic Wave (SAW) techniques was first published in my regular column in the December issue of the journal “South African Instrumentation and Control” (SAIC), published by

The SAW (surface acoustic wave) technique offers fascinating opportunities for many different styles of monitoring sensor. The first example seen many years ago really impressed me: it was called TorqSense, a torque measurement sensor applied onto a drive shaft, with no external electrical connections to the shaft needed. This used a SAW device mounted on a quartz substrate: the input and output sensors for the acoustic waves are separated by the length of this substrate, which changes as the quartz is deformed by the torque. Feedback creates a high-Q resonant circuit, and the resonant frequency changes as the quartz is distorted. RF excitation and monitoring of this resonance from an external unit gives a measure of the torque: this has been offered commercially by the UK based Sensor Technology for over 10 years.

Since then SAW techniques and sensors have been studied and researched by many universities, and sensors have resulted that measure temperature, pressure, viscosity, humidity, and even chemical concentrations. The idea is to choose a substrate or acoustic delay-line material between the acoustic transducers that is influenced by the environment to be monitored, such that it is stretched, or the acoustic path length changes in some other way. A recent market status report, by Mordor Intelligence, suggests that the total market for all such SAW sensor systems will be almost $4Bn by 2018.

The clever part in creating a sensor is to modify the acoustic properties of the piezoelectric material between two sensors in some way. Chemical and biochemical sensors for monitoring liquids have been created using a lithium tantalate piezoelectric with a micron thick coating of PMMA or cyanoethyl cellulose, which is sensitive to the chemical target, and keeps the surface waves near the surface, which are therefore influenced by the liquid properties.

Industrial flow applications

After collaborating with such university research for some years, in 2014 Bürkert saw the opportunity to develop a liquid flowmeter using SAW transducers, which could give major advantages particularly in hygienic applications – one of its key market areas. In this case, the SAW transducers were to be used to launch the ultrasonic pulse into the pipe wall of the flowmeter, which then leads to transmission of the signal diagonally across the fluid flow. The pipe wall and the moving liquid create the variable length acoustic delay line between opposing pulsed sensors, and fluid movement creates the change in this delay.

Burkert261_FLOWave_SAW_flow_sensor_pic1_PR2548_58253Effectively, Bürkert was using the SAW transducers as the upstream and downstream sensors for a time of flight type ultrasonic flowmeter. But also there is no intrusion into the flow tube, so the meter is suitable for ultra-pure applications like pharmaceuticals, water for injection and so forth, as well as food and beverage applications.

Development and field testing has covered the last two years, with a careful product release for suitable applications – typically initially used on low conductivity clean liquids, such as water for injection (WFI) in the pharmaceutical sector. Indeed one field test unit was installed in the supply line of a production filling system for infusion bags. Now, the Bürkert FLOWave range of flowmeters, covering DN15 to DN50 pipe sizes, is fully available for sale. This range of sizes covers the smaller bores typical of industrial requirements, in contrast to the larger ultrasonic flowmeters available from other suppliers. FLOWave is designed for hygienic use, and certified to EHEDG and 3A standards. The pipe has hygienic style end connections, and is internally finished to 0,8 or 0,4 microns: it is fully CIP and SIP tolerant, and indeed has been used to control CIP cycles, as the unit also provides a temperature measurement of the flowing liquid. It uses four SAW transducers, two on each side of the sensor pipe section, therefore acting as a dual path flowmeter. Flow measurement performance over the range 1-10 m/sec flow velocity is 0,4% of reading.


The latest development work has introduced density measurement and an acoustic transmission monitor parameter, which allow indications of the viscosity, bubble and suspended solids content of the liquid. This is useful in CIP process control, and also for monitoring milk in the dairy, during filtration. Bürkert claim an advantage over other styles of flowmeter, in that the unit is small and light in weight when used on a skid. Other applications now being investigated are for wort concentration monitoring in breweries, and homogenisation control in paint manufacture. Highly viscous liquids, such as glue, are also being monitored, where the full bore obstruction-free design is important.


Protect your flowmeter IP

trevor-forsterThe following comments come from Trevor Forster, the MD of Titan Enterprises, a specialist flowmeter manufacturer based in Dorset, UK. He recounts his experiences over the development of a new style of time-of-flight ultrasonic flowmeter, later called the Atrato, in their latest newsletter, called the Titan Flowdown. It is an interesting experience and maybe holds some lessons for all.

“A few years ago, Titan Enterprises filed a patent application for some new ultrasound technology we had been developing over the previous 12 months. On examination by the patent authority it transpired that someone else had the exact same idea and had filed some three months before us. Annoyingly this competitive filing was nine months after we had our first thoughts and six months after our first successful experiments. There were two valuable lessons here:

  1. File your ideas as soon as possible.
  2. Do not waste time in developing a completely viable idea before protecting the intellectual property behind the innovation.

As a consequence of this setback we had to revisit what we wished to achieve with our ring technology development. This project involved development of an ultrasonic device which was tolerant to variations in tube diameters due to the material, temperature or pressure. Our new idea was to section the device annulus into several segments which where independently acoustically coupled to the pipe but joined electronically. The benefit of this innovation is that it would provide us with a “flexible” crystal which can accommodate variations in the tube diameter as well as having a consistent acoustic connection.

Our developmental options were to make drawings, get the specially shaped crystals manufactured and then perform the tests. Alternatively we chose to get some miniature diamond cutting saws with appropriate boring burrs and make our own segmented crystals from existing larger crystals which we use on another ultrasonic meter. This enabled us to prototype and test our idea much more quickly.

The initial tests on the new device were extremely promising which gave us sufficient confidence to file our patent application while more accurate components were being manufactured and tested. This technology has formed the basis of our soon to be released Metraflow ultra-pure flowmeter and our developments with a new 1350 bar flow device.

The initial disappointment was a valuable lesson in getting intellectual property registered as quickly as possible especially with any rapidly developing technology.”


Editor’s comment:

From previous discussions about this development, the initial research and testing of the flowmeter concept was undertaken in co-operation with a University, using a research student, so the development was not completely ‘under wraps’, under the control of the company. Nevertheless in a fast developing technology area, many minds are grappling with similar perceived problems and solutions, so parallel work would have been going on elsewhere: an early patent filing is very important under such conditions! The ultra-pure nature of the Metraflow flowmeter arises as the flow tube is a simple straight glass or similar tube, and the ultrasonic transducers are all external. To register to receive further info on the Metraflow, please email Titan.

Fashions in sensor technology

I confess it was 50 years ago when I started looking at new technology for sensors. Back then, colleagues and I updated the old WW2 mine detector, using really low frequency (i.e. 1 kHz) magnetic waves to discriminate between ferrous and non-ferrous items, and assess the size and range of the target by the signal phase measurement. Here the electronics used ‘modern’ operational amplifiers, on a ‘chip’.

The 1980s

Ten years on, in the ’80s, the technology coming into vogue was ultrasonics, replacing float systems to make liquid level switches, and then, still using analog electronics, the first Doppler ultrasonic flowmeter appeared. With the availability of digital microprocessor circuitry, timed pulses transmitted through the air down to the surface of a liquid led to non-contact liquid level measurement, and major success in the automation of sewage sump pumping systems. (The success lasted maybe 30 years, as when the mobile phone business created low cost microwave components, similar systems based on radar began to take over in this market.)

The next leap forwards in the mid-’80s was the time-of-flight ultrasonic flowmeter – actually achieved with discrete digital circuitry, which was faster than the available microprocessors. The technology was originally developed at Harwell, for measuring liquid sodium flows in nuclear reactors, but these flowmeters found major application in monitoring clean water flows, primarily in water distribution mains. Over the next 25 years the technique was picked up by commercial interests, and continually refined, introducing clamp-on sensor systems, and adapting the technique for gas flows as well. Even domestic gas meters were introduced using the same principle. Eventually the microprocessor speed became fast enough to achieve the flow measurement accuracy needed – using multiple sound paths – for the fiscal measurement of oil flows, which is now one of the major applications, along with similar gas flow measurement tasks.

Other sensors where I was not initially involved were in the fields of gas detection – where for flammable gases, Pellistors created a major business area – and fire detectors. It seems that UV and IR fire detection systems are still seeking the best approach. Possibly because of the awareness brought about by the Internet, the pace of change and the commercial opportunities, the large corporations are quick to acquire small spin-off companies from university or other research after any small success, because of what technology they may have discovered: they do this ‘just in case’, to protect their market position.

Current developments

The area I see as most important currently, and a fruitful area to flag up for research projects, is in any style of optical analytical measurement sensor. Specifically, the component that brought this into industrial instrumentation was the tuneable diode laser (TDL), developed prior to 2005 for the telecommunications industry, to transmit telephone conversations and data down fibre-optic cables. Around 2007 Yokogawa acquired a business from Dow Chemicals, which used TDL sensors for near-infrared absorption (NIR) measurements of a gas mixture, which gave the proportions of oxygen, carbon dioxide and monoxide, and water vapour. This allowed the unit to be used as a combustion analyser for industrial furnaces, boilers etc.

Over the last 10 years this area of technology has grown in importance, and in its capabilities. Spin-off companies have emerged from various universities, like Manchester and Glasgow. A significant task in these developments is the application of the solution to an industrial problem: it needs the two factors of solving both the technical design and the industrial application. Cascade Technologies was established in Glasgow in 2003, and their analysers were initially targeted at marine flue gas emissions monitoring. From 2013 they added a focus on pharmaceutical gaseous leak detection, and also the process industry, on ethylene plants. Their technology allows multiple gases to be measured simultaneously. The Cascade business has now been acquired by Emerson.

Another closely market-focused supplier of NIR analytical systems is TopNIR Systems of Aix en Provence, in France, actually a spin-off business from within BP. TopNIR use their systems to analyse hydrocarbons – both crude oil and processed products – to allow a refinery operator to know how to most profitably blend the available components into a final product, as well as to minimise any quality give-away in blending the different grades of gasoline and diesel. TopNIR quote the annual benefit to a typical refinery at $2 to $6 million, with an implied investment spend of up to $2 million!

This article was first published in the May 2017 issue of “South African Instrumentation and Control” published by


Emerson to work with Flexim

Emerson Automation Solutions and Flexim, the clamp-on ultrasonic flowmeter specialists, are to collaborate, to help process customers optimise their flow process design, flow meter selection and flow meter installation on capital projects. This will enable them to reduce execution risk and costs.

With customers under severe pressure to reduce schedule and cost targets on capital projects, Emerson project teams, using the Flexim clamp-on, ultrasonic flow metering portfolio in combination with the broader Emerson in-line flow meter products, are able to consult early and throughout the project cycle to reduce engineering, piping and installation costs as well as schedule risk.

Flexim non-intrusive flow meters are the market leaders in clamp-on, ultrasonic technology and provide the best reliability and the most advanced capability when addressing difficult applications with a non-intrusive flow solution. This co-operation will improve delivery of the exact flow solution needed by clients while supporting  ‘Project Certainty’ – the Emerson approach that is said to enable top-quartile performance in capital projects.

By empowering project teams with flow expertise to work with clients early in project phases, Emerson has consistently eliminated cost, accommodated change and reduced complexity on capital projects. The non-intrusive nature of the Flexim ultrasonic flow meters makes this product a powerful contributor to reduced engineering, piping and installation costs as well as schedule risk, given that it can be installed after piping is fabricated. Emerson and Flexim will collaborate to ensure less time is spent on engineering and installation by selecting the optimal flow solution for a given application and applying the most comprehensive flow portfolio available.

“In today’s market, we are seeing that our customers are looking for us to advise them early in their project cycle on technology to ensure streamlined and cost-effective project execution,” said Bret Shanahan, vice president of flow solutions, Emerson Automation Solutions. “We are pleased to be working with Flexim to provide our clients with the most appropriate flow solution that can be applied and support greater capital efficiency.”

“Flexim is excited to partner with Emerson on capital projects; our flexible, world-class, non-invasive meters are a perfect fit with the experienced Emerson project teams,” said Guido Schwanekamp, managing director for sales and marketing at Flexim. “Together we will be able to offer fully customised solutions that are tailor-made for a wide variety of capital projects, reducing capital expenditures while increasing efficiency for our clients and reducing total cost of ownership at the same time.”

The new Process Atrato ultrasonic flowmeter

A new flowmeter for small bore liquid flows has been introduced Titan Enterprises, an enterprising British company, who are a long established manufacturer of liquid flowmeter systems. Their first ultrasonic meter was introduced in around 2010, after a long development programme in co-operation with Prof Mike Sanderson at Cranfield University, and was called the Atrato. This unit was launched for the typical markets served by Titan, of laboratory testing, drinks dispensing, cooling systems, pilot plants, fuel cells, pharmaceutical applications and OEMs – and offered a 200:1 turndown, 1% accurate obstructionless straight through meter with a 4-20mA output. Materials were mainly PEEK and borosilicate glass or stainless steel for the flow tube, but the BSP or NPT male fittings were available in stainless steel. A very clever and high performance flowmeter for flows up to 20 Litres/min.

The Launch in 2010

Regrettably, while having worked with Titan for many years prior to 2010 on their PR and promotion, a high flying expensive agency was brought in to promote the Atrato, so it disappeared off my radar. I should not say much about whether it has been seen by anyone else since then, because I don’t have any info: but why are you reading this?

Now a new launch has been announced by Titan, of the Process Atrato flowmeter: a new version of the basic flowmeter, now ‘packaged for the process and control environment’.

The Titan Atrato for the Process Industry


This unit is built from 316 stainless steel and PEEK, plus an elastomer seal to suit the application, and has the on-board electronics sealed to IP65. From the photo you can see that the threads into the stainless steel process connection (at the top of the flowmeter) are female. The lower screw thread is for an M12 four pin electrical connector. The unit is suitable for 65 Celcius and 25 bar process conditions: the non-process Atrato can operate up to 110C if the electronics is installed remotely, so presumably this might be a future development. Flow range covered is 2mL/min to 15 Litres/min, using four flowtube sizes.

Each of the four models covering the different flow ranges is configured to offer the same pre-set ‘K-factor’, which is quoted to assist OEM use and interchangeability: but it also highlights that the electronic output available on these “process units” is a PNP and an alternative NPN pulse train, quoted as a ‘frequency’ output. Presumably this relates back to the pulse output style as was provided by the other Titan turbine and positive displacement flowmeter sensors. A separate power supply, from 8-24VDC, is used to power the unit.

A few criticisms

The other surprise for me was that the meter is pictured, and obviously intended for installation, ‘upside down’, with the electrical connections and housing below the flow line. When this Process Atrato is really an equivalent to a thermal mass style gas flowmeter application, but on liquids, you would think it would be sensible to have it looking similar to these other, well-known gas flow devices. The reason for this cannot be that it needs to allow entrained air to escape, as the flow tube is just a straight tube, with no complicated connections which might trap anything.

For the engineers who can see through these confusion factors, the device is a very effective flowmeter, 200:1 turndown, +/-1% accuracy over 2-100% of range, while working with viscous as well as non-viscous fluids – with the standard Atrato features of linearity, no moving parts and fast response time. Plus the PR says it will offer a ‘reduced cost of ownership’, but does not specify what this is compared with…..surely the point is that there is not much else on offer to provide this performance, except maybe a micro-Coriolis meter.

If Only….

The pity is, ever since launching the Bestobell Doppler flowmeter in 1976, and the Platon Kat in 1998, I’ve been looking forward to being involved in the launch a decent ultrasonic flowmeter for clean liquid process applications…..

Maintenance-free Non-contacting Bulk Fuel Tank Monitoring

Pulsar Process Measurement have supplied non-contacting ultrasonic volume measurement equipment with associated remote plant mimic software to help solve an issue for Northern Rail at three sites; their Newton Heath LMD (Light Maintenance Depot) near Manchester, Blackpool LMD and Barrow LMD, allowing them to control the ordering, delivery and usage of fuel more efficiently.

Northern Rail’s contractor Austin-Lenika, who were engaged in a wider project on site, had identified that the existing level indicators were not suitable for the application and were, therefore, not reading the level correctly. Austin-Lenika approached Pulsar for a solution. They specified that new equipment should provide a measurement of the volume of fuel in the bulk tanks with a target of ±1% accuracy, allowing staff on site to monitor fuel usage and transfer and pinpoint the optimum time to re-order fuel. They also wanted to have both local display of level on the storage tanks and to be able to remotely monitor levels across the entire tank farm of eight fuel vessels, plus three additional bulk tanks.

Pulsar supplied Ultra 3 non-contacting ultrasonic level measurement controllers with associated dB series transducers. The transducers were mounted into flanges at the top of the fuel tanks, and operate on a ‘time of flight’ principle, an ultrasonic signal reflecting back to the transducer from the surface of the fuel. The measurement is reliable and accurate, with sophisticated signal processing by Pulsar’s dedicated DATEM software system. In addition, the Pulsar Ultra Controller can calculate volume based on almost any standard tank shape, taking the tank dimensions and making the calculations necessary to convert them into the volume of fuel in the tank.

Pulsar on-tank hardware and remote display screens

Pulsar ‘on-tank’ hardware and UltraScan display screens

Pulsar also supplied UltraScan software, which uses the RS485 Modbus output of the Ultra to provide a screen display of both levels and alarms. UltraScan can operate either on a site basis or can bring together measurements from a variety of sites.

Staff at Northern Rail are using the system very effectively. Austin-Lenika tested the system by comparing delivered fuel from a tanker to measured levels from the Pulsar system, finding a variance from a 6000 litre delivery of ‘within 60 litres’, achieving the ±1% target.

New Krohne ultrasonic flowmeter for superheated steam

With the Optisonic 8300, Krohne presents a dedicated ultrasonic flowmeter for the measurement of superheated steam. The 2-beam flowmeter stands out with a measuring accuracy of 1%, high repeatability, and a large dynamic measuring range. Typical applications include boiler and plant efficiency monitoring in power plants, energy balancing or inter-company steam billing.

As downtime of steam pipes is very costly and must be avoided, Optisonic 8300 was built for long term use: it features a full bore flow sensor without moving parts or obstructions, and an overall sturdy and robust construction with no cables or sensitive parts exposed. Therefore, it can uphold its measuring accuracy without maintenance or subsequent calibration for up to 20 years, while keeping operating costs at a minimum. If verification of the measuring accuracy should become necessary, it can be provided by using the flowmeter diagnostics, without removing the flowmeter.

With nominal sizes ranging from DN 100 to 1000, or 4” to 40″, Optisonic 8300 is particularly suited to high flow rates. Pressure rating up to 200 bar (3625 psi) and temperature rating up to 540°C / 1004°F are available, higher requirements can be considered on request. With temperature and pressure sensors also connected to the device, the integrated flow computer can calculate steam mass flow.

Optisonic 8300 adds to the Krohne portfolio of ultrasonic process and custody transfer meters for liquids and gases, which now cover the range from compressed air to cryogenic liquid natural gas (LNG).