Confusion over radar level measurement

We have learned not to get too confused over suppliers using buzz-words and clever marketing names, but recently it seems the major level measurement system vendors have been introducing new and higher radar frequency systems as their latest development – and therefore, by implication, maybe the best. We were used to 6 GHz, and then 26 GHz radar frequencies, but why should we suddenly go to 80 GHz? Then, perhaps just to add a little excitement to the mix, Endress+Hauser started talking about 113 GHz!

113GHz_Key_Visual

The E+H radar line up that offers 113GHz!

This article was first featured in the journal South African Instrumentation & Control in September 2017, a journal published by Technews

Let’s dispel a few myths. Firstly, in the same way that lasers for fibre-optic communications systems made the technology available to create infrared optical systems for process gas analysers, and mobile phone technology possibly provided the hardware for the first radar level measurement systems; the 80 GHz versions are a result of measurement technology made commercially viable on the back of production investment in the distance measurement systems and parking sensors used in modern cars. So the suppliers take the available sensors and chipsets to create a new industrial product, and then have to find the best applications – in this case, the ones that might benefit from the 80 GHz.

Secondly, E+H do not have a 113 GHz system, this is a marketing statement, made to catch attention – ‘with a wink’ is their expression. They claim a ‘complete radar competence of 113 GHz’ because this is the sum of the many different frequencies their different sensors use! These are 1, 6, 26 and 80 GHz.

So why have different frequencies?

Possibly the best explanation for the applications suited to the different frequencies has been provided by the Rosemount measurement division of Emerson, in their “Engineer’s Guides”. The Emerson expertise stretches back many years, having acquired the Saab Tank Radar business. Per Skogberg, from the Gothenburg HQ in Sweden, separates the devices into low, medium and high frequency, to generalise.

Radar signals are attenuated, i.e. they lose signal strength as they pass through the air, or vapour, above the liquid. High frequencies are more severely affected than lower. When the air has moisture, steam or liquid droplets (from spray or filling) present, the attenuation is higher. Equally in solids applications, dust particles have the same effect. So low and medium frequency radar are best when there is dust or moisture present.

At lower frequencies, the wavelength is longer (30-50 mm), so surface ripples in a tank have a small effect. At higher frequencies, surface ripples and foam on the surface can be a problem. But the shorter wavelength of the high frequency units (4 mm) allows accurate operation over short ranges, for example in small tanks. The higher frequency units can use a smaller sensor construction, so the unit is easier to install. The beam angle is narrower, so it can be aimed at a smaller target area and therefore can be positioned more easily to avoid any obstructions in the tank. But even this can be a disadvantage, as the installation needs to be exactly vertical and any turbulence of the surface during filling or stirring can cause the signal to be lost temporarily, in larger tanks.

When reading these suggestions, it is important to remember that Emerson does not offer an 80 GHz unit yet, so their marketing approach would naturally bias users to look at low and medium frequency units. The suppliers of high frequency units (Vega, Krohne and E+H) would point out that in many liquid storage tanks the surface is undisturbed, since any foam, turbulence and significant ripples (>2 mm) caused by filling or liquid transfer will only cause short-term interference. Plus the small antenna size and short range performance make 80 GHz units very useful for smaller process vessels and tanks.

Radar system types

There are two types of radar systems, Guided Wave Radar (GWR) and Free Space Radar. The GWR systems use a conducting rod, or similar, extending down into the liquid, often working in a stilling chamber attached to the main process tank. These operate at low microwave frequencies, and are independent of surface turbulence and foam. They are useful for shorter range measurements and interface measurement between liquids, as well as long ranges.

The Free Space Radar systems are more widely used, since they are top-mounted with nothing in the tank: indeed, some can operate through non-conducting windows in the tank roof. Low and medium frequency radar systems generally transmit a signal pulse and measure the liquid distance by the time delay for the returned pulse. High frequency (80 GHz) systems use an FMCW radar measurement, where the frequency of the transmission is swept, and the frequency difference of the returned signal is measured to assess the distance. The FMCW technique is also used at 26 GHz in some recently launched sensors.

Radar systems can transmit their measurement data using 4-20 mA, fieldbus systems like HART, FF, Profibus PA and Modbus, or indeed via wireless systems like Bluetooth. The low and medium frequency pulsed radar systems generally operate over a two-wire interface: some of the higher frequency FMCW systems require more power and use a separate power connection.

Major applications

Simple low-cost radar level measurement sensors have been specifically designed for water industry use, in sewage sumps and flume flow measurement, by Vega and Endress+Hauser. Vega suggest that 40,000 such sensors are now in use in the water industry, mainly in Europe, and claim their total output of such sensors exceeds 550,000 units over the last 25 years.

Several of these devices use simple Bluetooth interrogation and programming from a handheld PDA: E+H demonstrates this at its facility in Maulberg, working on the stream that runs through the factory complex, as seen below.

Micropilot_FMR10_FMR20_on test stream at Maulberg, with operator using Bluetooth

Both E+H and Vega produce further industrial units for use on process vessels, and storage vessels for solids and liquids. Recently, E+H has extended its capability to add long-range units, such as the 80 GHz FMR62, working at up to 80 m range, with an accuracy of 1 mm. Other units work up to 125 m range, at 3 mm accuracy. These units will eventually be aimed at the large petrochemical industry storage tank markets, and specifically are working towards use for custody transfer duties.

Krohne have similarly announced a new range of its 80 GHz Optiwave sensors. Some of these can even operate at up to 700°C, for example for use on molten salt vessels in solar power plants. Lower specification units rated at up to 150°C can be used through a tank roof made of plastic, or similar materials. Suitable for small or narrow tanks, the unit can measure ranges of up to 100 m. Krohne also offers lower frequency Optiwave systems for use on solids and powders, or to electronically monitor the float position in magnetic level indicator columns attached to process vessels.

Postscript: Krohne is organising a webinar with the title “80 GHz Radar Level – Allrounder or Overrated?” to discuss their recent developments with such systems. This webinar will take place on 18th October 2017 at 3pm London time/10am New York time.

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The mystery of intelligent sensor diagnostics @ProcessingTalk #PAuto

The fashion, or trend, that has developed over the last few years for process and analytical instrumentation sensors is to use their on-board intelligence to monitor their own performance status. They achieve this by monitoring and tracking various diagnostic measurements – secondary parameters where consistent values are said to indicate the sensor is working as it should, and has not been subject to any changes since leaving the factory.

This approach is easily understood if you consider the possible effects of exposure of a sensor to excessive temperatures, which might soften the potting or glues holding a sensor to a ‘window’ – and it can be expected that this would be detectable. The addition of a diagnostic sensor, such as a temperature probe, within the sensor housing, could also be an option for checking the sensor condition, and alarming if the sensor exceeds a high or low set-point.

But how else do sensors check their own performance, and how relevant are these “checks”? This topic was discussed in the latest issue of the South African Journal of Instrumentation and Control, August 2017 issue: SAIC is a journal produced by technews.co.za.

Modern (intelligent?) sensors

So, over the past two years of attending and listening to presentations, and reading relevant articles describing the advantages of self-monitoring systems and sensor diagnostics, waiting for an engineer’s explanation as to how the clever monitoring system actually tells the factory instrument engineer anything, it is a bit of a disappointment to report that there seem to be no suppliers that actually make any significant disclosure. This applies across sensors ranging from ultrasonic and Coriolis flowmeters, electromagnetic flowmeters, level measurement systems using radar or ultrasonics, and level alarms. Obviously all the major suppliers are involved in such equipment, and compete with each other, but this secrecy seems a little extreme.

The problem is possibly that until a manufacturer can point to a failure that was detected – or anticipated – using their diagnostics, and decides to publish it, the user population has no idea what systems might actually work. But equally, by publishing a success for the diagnostics, the same manufacturer is saying that one of his sensors failed – and that is a very unusual event, these days. Plus also maybe not something they would wish to publicise.

The older approaches

The whole idea of diagnostics and sensor monitoring has been around for a long time. From personal experience with Bestobell Mobrey, in the 1980s, Mobrey launched an ultrasonic version of a float switch, the ‘Squitch’, which switched a two wire mains connection through a load circuit. When not alarmed it just sat there taking a small control current. For customer reassurance that it was operating in this quiescent state, there was a blinking red LED to show that the sensor was ‘armed’ and operating normally. Mobrey called that a heartbeat indicator, a term that is now used more widely.

For custody transfer flowmeters, the classic approach to validate confidence in the reading is to use two meters in series, and check that both give the same answer. This has progressed to having two separate ultrasonic flowmeters mounted in the same flowtube, on some installations.

For the more safety conscious plant there are often requirements for duplicated sensors for such duties as high level alarms, where two different technologies are used by the sensors – e.g. by mixing float, capacitance or ultrasonic level alarms.

The modern approach

It seems that the ultimate approach is to let the sensor supplier link into your plant automation and data system to interrogate the sensor, and he will verify the measurement and performance diagnostics on a regular basis. With many and varied sensors, this leads to a lot of external interrogation of your plant assets, and possible worries over losing control of your plant.

Overall, it begins to look as though it is becoming impossible for a discerning plant engineer to decide which supplier has the best performing diagnostic system to monitor the relevant sensor’s performance. Rather like opening the bonnet of a modern car, and deciding it would be best to take it to a garage!

At a recent lecture on this subject, held by the InstMC Wessex section in co-operation with Southampton University, a detailed discussion concluded that the sensor suppliers now have all the real expertise in-house and a normal plant engineer could not be expected to cover the depth of this technology for all the many sensors and other equipment within his control. In the end the decision as to ‘which supplier to use’ returns to your own previous experience, including the service and support that has been and is now on offer, and the suitability of the product for the money available for that sensor task.

E+H reports on 2016 sales

The report that follows was first published on Eoin O’Riain’s Read-Out.net website in Ireland last week. It gives the first report on Nick Denbow’s visit to the E+H European presentation in Basel, which included a tour of the Maulberg manufacturing operation for level measurement products, like the NMR81 radar based systems. Financial results for the 2016 year were discussed with the 70+ journalists and media analysts attending.

This year, Endress+Hauser expanded the presentation of their annual financial results, inviting journalists from not only Germany and Switzerland, but including others from Belgium, the Netherlands and Great Britain. In all 70+ attendees heard Klaus Endress and Matthias Altendorf say that the consolidated Group sales fell slightly between 2015 and 2016, by 0.2%, achieving Euro2.1Bn. This fall was actually only because of currency fluctuations. “Currencies created a headwind for us last year,” said Altendorf. Working from the value of sales in local currencies, sales in total actually increased by 2.1%. Whilst the Group is family owned, their annual report is published and audited to the standards expected of any other international business.

CEO Matthias Altendorf emphasised that “When compared to overall industry growth, we held our own”. E+H performed well in Europe, but sales in America declined. Africa and the Middle East experienced solid growth, but in the Asia-Pacific region business stagnated.

Within Europe, the best performances for E+H came from Ireland, Italy and Finland. The best performing sectors in all countries were food & beverage, life sciences, and water & waste water. Overall business declined in oil & gas, chemicals and primary industries like metals. The power and energy industry sectors showed good performance outside Germany, where E+H also felt the effect of weak German exports and some internal restructuring. The oil & gas decline badly affected sales in USA, UK and Norway, although the UK sales centre gave a good performance by aligning efforts with other active market sectors.

Investment continues.

E+H plans for investment and growth continue for the current year. Earlier in the week a new factory extension was opened in Reinach, where flow products are manufactured. (see Read-out Signpost – “Flowmeter output growth requires new facilities” – 5 May 2017).  The journalists were given a tour of the manufacturing facility in Maulberg (D), where a new extension to the production area is in operation, and a new NMi level measurement system calibration facility for radar based systems has just been completed. This is certified suitable for calibration of the Micropilot NMR81 radar system, working at 80GHz, which achieves a +/-0.5mm accuracy over a 30m range, for use in oil storage tanks and oil terminals. There are plans now to extend this calibration facility to allow such calibration out to 40metres, as well as to extend the factory yet further: 1912 people work at E+H Maulburg, and 5200 people in the Basel region, out of the total E+H staff of 13,000.

Analytical measurements

The biggest growth area in E+H is actually in the analytical instruments that use Raman spectroscopy to analyse liquid and gas streams on-line. The major industries now applying this technique are within the life sciences sector, where immediate analysis of input and both gaseous and liquid effluent streams enables much closer control of biochemical and fermentation processes. Indeed the 2017 issue of the E+H corporate magazine “Changes” features a major focus on new applications in the Life Sciences industries.

Other new analytical techniques are developed for monitoring water treatment processing, for example in the new Swiss plants which by law have to have a fourth stage of purification, to remove hormones, phosphorus and other drug residues. The strength of E+H here derives from their strategic decision a few years ago to invest in the process analytical area, particularly in the field of spectroscopy, acquiring Kaiser Optical, Analytik Jena and SpectraSensors. “Our analytics strategy has been validated by the market,” said Matthias Altendorf.

Bundling IIoT activities

The acquisition of German SensAction AG in early 2017 also ties in with Strategy 2020+ which was rolled out last year. The company, headquartered in Coburg (D), manufactures innovative systems for measuring concentrations in liquids. Endress+Hauser is tackling the challenges of digitalization by bundling a number of activities. A new subsidiary in Freiburg in Breisgau,(D), is working exclusively on products, solutions and services related to the Industrial Internet of Things (IIoT).

The significance of digitalization can also be seen in the growing number of patent registrations. There were 273 first filings in 2016. The intellectual property rights portfolio thus boasts more than 7,000 active patents. R&D spending rose to 7.8 percent of sales. Endress+Hauser introduced 64 new products to the market. “We are investing in innovation for our customers,” underlined the CEO.

Trends in automation.

The focus for E+H sales and their customer base is broadly on automation engineers, so it was interesting to hear Matthias Altendorf comment that the statistics for industrial output show that the Britain has now dropped out of the top 10 countries in terms of automation business activity, whereas they had held a prominent position there some years ago.

The other aspect of interest was that there are distinct differences between countries, in terms of the sex of the engineers involved in the major projects served by E+H. In Germany they are mostly male, whereas the majority of engineers in Turkey are female. In South Korea and India there are high percentages of female engineers (and engineering journalists). Also, by industry, it is noticeable that in the biochemical and life science sectors the engineers are predominantly female.

Power Industry Boiler Water Level Measurement Techniques

The March 2017 Inst Measurement and Control Technical Seminar evening will be hosted by Doosan Babcock in Manor Royal, Crawley, on Tuesday 21st March 2017.

This will be a tri-company, collaborative event, presented by Doosan Babcock, and also featuring contributions from Vega and TC-Fluid Control. It is aimed at providing attendees with a useful insight into industrial measurement application challenges in order to further their professional development knowledge.

Drum Level Control

The first presentation by Doosan Babcock will discuss Drum level measurement using DP Measurement and Hydrastep Measurement techniques.

Power station Steam Drum Level measurement is required for drum level control, Burner Management System (BMS) protection and Code compliance. Drum level is both a critical and difficult measurement to make. At steady state conditions, considerable turbulence in the drum can cause the level to fluctuate. A changing rate of water inflow and steam outflow adds to the potential for measurement error. The DP Measurement technique uses the difference in pressure between a head of water in an external reference column and the level in the drum. The density of water and steam vary appreciably with pressure, so the differential pressure obtained at any given level will vary as boiler pressure changes.

The Hydrastep technique detects the conductivity variation between the steam and the water. The electrode principle is an efficient system for measuring drum water levels.

Microwave Technology

Vega will explain how microwave technology can tackle a wide variety of applications associated with steam boilers. Non-contact or guided wave techniques have the ability to measure reliably, even with fluctuating temperatures up to 450C combined with pressures of up to 400 bar. Measurement is virtually unaffected by pressure and temperature changes. Top mounting makes installation and maintenance easy. In many cases microwave transmitters provide an alternative to legacy equipment for both solids and liquids. SIL qualification and boiler approval now enables microwave technology to  be used directly on steam boilers, with special modifications to compensate for saturated steam effects.

Visual/Glass and Boiler Steam Glass level gauges

untitledVisual/Glass and Boiler Steam Glass level gauges are a requirement on steam boilers for visual verification of the level control system, and will be discussed by TC-Fluid Control. Magnetic level gauges have many applications on and around the boiler, providing visual level indication whilst minimising potential leak paths, and can be used as an alternative to one of the glass level gauges on the boiler drum. Simple, robust technology provides a highly visible indication of process level at pressures of up to 400 bar and temperatures up to 450C.

Postscript: Wessex IMC Section meeting

Vega Controls will also give a talk to the IMC Wessex Section meeting on 15th March about the technology behind their 80GHz radar liquid level measurement systems. The talk will include live demonstrations, and takes place at the Forest Lodge Hotel, at Lyndhurst. A video is available that shows their new sensor.