A Coriolis mass flow meter is known as a very accurate instrument and it has many benefits compared to other measuring devices. However, every measuring principle has its challenges, as also the Coriolis principle. It can be a real challenge using Coriolis instruments in low flow applications in the heavy industry where you may have to deal with all kinds of vibrations. In this blog I would like to share my experiences with you regarding this topic.
The Coriolis principle
Coriolis mass flow meters offer many benefits above other measuring devices. First of all Coriolis flow instruments measure direct mass flow. This is an important feature for the industry as it eliminates inaccuracies caused by the physical properties of the fluid. Besides this benefit, Coriolis instruments are very accurate, have a high repeatability, have no moving mechanical parts and have a high dynamic range, etc.
Read more about the importance of mass flow measurement and the relevance of Coriolis technology in a previous blog.
Do vibrations influence the measuring accuracy of a Coriolis mass flow meter?
In industrial applications, all kinds of vibrations with different amplitudes are very common. A Coriolis meter measures a mass flow using a vibrating sensor tube, which fluctuation gets intentionally out of phase when the fluid flows through. As explained in the video [link] at the end of this article.
This measurement technique is somewhat sensitive to unwanted vibrations with a frequency close to the resonance frequency of the sensor tube (this depends on the sensor tube design, e.g. 360 Hz) or a higher harmonic of this frequency (see picture below).
The likelihood of the occurrence of these unwanted vibrations is higher in an industrial environment. Coriolis flow meter manufacturers do their utmost to reduce the influence of vibrations on the measured value by use of common technical solutions, such as using:
- higher driving frequencies
- dual sensor tubes
- different sensor shapes
- mass intertia (e.g. mass blocks)
- passive and active vibration compensation
So yes, vibrations can influence the measuring accuracy of your Coriolis flow meter, but only if the vibrations have a frequency close to the resonance frequency. What can you do about this? This depends on the kind of vibration.
What kinds of vibrations do exist?
In an industry zone frequencies can be generated by:
- environmentally related vibration sources (such as: truck, rail transportation, industry activities)
- building-based vibration sources (mechanical and electrical installations, like air conditioning) or
- usage-based vibration sources (installed equipment and machines, e.g. pumps, conveyor belts).
These vibrations travel through a medium like the floor, in the air, through pipes or the fluid itself. If these vibrations disturb the Coriolis frequency, the measured flow could be incorrect in some extent.
To minimise the effects of vibration it is useful to identify these sources. Sometimes, it is possible to move the flow meter just a little bit, turn it (Coriolis flow meters are in most cases less sensitive to vibrations if the meter is rotated 90 degrees), make use of a big(ger) mass block, use flexible tubes or U-bend metal tubes or use suspension alternatives.
How could you check the performance of a Coriolis flow meter?
A well performing flow meter and controller will give the best process result. Therefore, it is advisable to test a Coriolis flow meter in your application if you expect heavy industrial vibrations before you trust it to the full extent. Be careful when filtering the measuring signal. In some cases it makes sense (e.g. when a quick response isn’t required), but if you want to test the performance of a flow meter, filtering could blur your judgement.
If in specific circumstances the Coriolis flow meter isn’t performing the way it should, the operator will see a shift in the process output – for example in an application dosing colour to a detergent it can result in differences in product colour by incorrect dosing and/or unexpected measuring signal behaviour. In these cases it makes sense to check the raw measuring signal (without filters!), because it will give you a good insight in the performance of the flow meter. Ask your flow meter manufacturer how to switch off all signal filtering.
Standards regarding vibrations
Remarkably, the influence of external vibrations is not clearly defined in a standard for Coriolis flow meters. Several standards are written about vibrations, but none in respect to measuring accuracy in relation to vibrations. However, two useful standards in relation to vibration are:
- IEC60068-2, Environmental testing for electronic equipment regarding safety
- MIL STD 810, Environmental engineering considerations regarding shock, transport and use
As a user of Coriolis flow meters it is important to understand your application, especially about potential external vibration sources. As low flow Coriolis specialist we work together with knowledge partners like the University of Twente and TNO (a Dutch organization for applied scientific research) to get a continuous improved understanding of this topic.
With in-house test facilities we are able to do special vibration tests. Together with the experience we gained from customer applications and custom made solutions, we are always aiming for improving our Coriolis flow meters to give our customers the best performance they need.
Watch our video explaining the Coriolis principle
Learn more about the Coriolis measuring principle
Read more about the importance of mass flow measurement and the relevance of Coriolis technology in a previous blog.
Check out our success story using Coriolis mass flow controllers for odorisation of our natural gas.
Anhydrous Ammonia Control for Nitrogen Oxides Reduction
As a technique to reduce the level of Nitrogen Oxides (NOx) in boiler or furnace exhaust gases, Selective Catalytic Reduction (SCR) has been around for years. SCR is a technology which converts Nitrogen Oxides (NOx) with the aid of a catalyst into diatomic Nitrogen (N2) and Water (H2O). A reductant agent is injected into the exhaust stream through a special catalyst. A typical reductant used here is Anhydrous Ammonia (NH3).
A customer of Bronkhorst, who has been selling and servicing boilers and pumps for commercial and industrial applications for over 50 years, had been using a mass flow controller (MFC) which was not reliable and robust enough for the application and thus their customers were suffering from poor ammonia measurement and control.
Why use mass flow measurement in Ammonia Control?
Some NOx reduction systems are liquid ammonia based, and others are gas based ammonia. Whatever the state of the ammonia in the NOx reduction system Bronkhorst can offer accurate ammonia measurement and control. Systems in the field today are using the MASS-STREAM (gas), IN-FLOW (gas) and Mini CORI-FLOW (liquid) to accurately control the ammonia being injected into the exhaust gas stream so that proper reaction takes place without ammonia slip. Ammonia slip is when too much ammonia is added to the process and it is exhausted, un-reacted, from the system; effectively sending money out the exhaust stack.
There are very strict federal and state air quality regulations that specify the allowable level of NOx which can be released into the atmosphere and there can be very heavy fines if those levels are exceeded. The company needs to provide their customers with a reliable and robust solution. The application demands a robust and repeatable mass flow controller that is at home in industrial environments.
What kind of Mass Flow Meter or Controller can be used here?
In the NOx reduction system serviced by our customer the mass flow controllers are used to control the flow of anhydrous ammonia (ammonia in gas state) into the exhaust gas of a boiler or furnace where it is adsorbed onto a catalyst. The exhaust gas reacts with the catalyst and ammonia which converts the Nitrogen Oxides into Nitrogen and Water.
Bronkhorst recommended a mass flow controller – from the MASS-STREAM series - using the CTA (Constant Temperature Anemometer) technology which is ideal to avoid clogging in potentially polluted industrial gas applications.
Let me explain a bit about the working principle of this kind of mass flow controller and why it is suitable for an application like this.
The CTA (Constant Temperature Anemometer) principle is essentially a straight tube with only two stainless steel probes (a heater and a temperature sensor) in the gas flow path. A constant temperature difference between the two probes is maintained with the power required to do so being proportional to the mass flow of the gas. This means the MASS-STREAM is less sensitive to dirt, humidity, or other contaminants in the gas, as compared to a by-pass type flow meter that relies on a perfect flow split between two paths. The thru-flow nature of the CTA technology is ideal to avoid clogging in potentially polluted industrial gas applications. The straight flow path and highly repeatable measurement and control capability, combined with the robust IP65 housing, allows the MASS-STREAM to thrive in tough applications.
- Watch our video animation, explaining the functions and features of the Bronkhorst Mass Flow Meters and Controllers for gases using the CTA principle.
- Check out the top 5 reasons why to use mass flow controllers with CTA measurement.
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The temperatures are sky high! All winter you've thought about going camping, travelling with your caravan and planning precious family trips. Finally now it’s the time to leave everything behind, and for a moment, forget the busy daily live and struggling at home. However, everywhere you go, Bronkhorst is travelling with you. Bronkhorst plays a role in many more applications than you think, also when you go camping. Let me guide you through some mainstream products you often see at a camping site, and the involvement of mass flow controllers.
If you are travelling to your holiday destination by car, you will constantly look at some Bronkhorst solutions. Let’s start with the dashboard of your car. Many cars have a leather dashboard; at least, it looks like leather. A major company manufactures ‘skin’ that covers a car's dashboard, to give it this ‘leather look’. The skin is produced by spraying liquid, coloured polyurethane into a nickel mould. A Coriolis mass flow controller combined with a valve forms the basis of this solution to accurately supply external release agent to the nickel mould surface.
But also the foam within the dashboard is manufactured by using Bronkhorst products. To create foam, a gas is added to a mixture, containing acrylonitrile-butadiene-styrene (ABS) or polyvinyl chloride (PVC), to give it the right volume. Too much gas will make the foam unstable, too little and you’ll get a heavy solid block. Therefore, it is utterly important that the correct amount of gas is added with an accurate gas flow controller.
If you look beyond your dashboard, you’ll look through the front window of your car. To control the light transmittance of glass, but also to make glass water repellent, protect it from mechanical and chemical stress, increase the scratch resistance and shatter protection, thermal mass flow controllers are used for the coating process. By controlling individually process gas flows, film thickness uniformity improvements are achieved.
Coating on headlights
When polycarbonate was introduced as a replacement for headlights glass in the early 1980s, new problems arised. Headlights are subject to a harsh environment. Due to the position in the front of a car, critical parameters for lifetime and performance are weather ability, scratches and abrasion. To protect headlights from these factors, scratch and abrasion coatings have been developed that are sprayed on the headlights with the help of robots in which Coriolis mass flow controllers control the flow to the spraying nozzles.
However, surface treatment is not only applicable for glass and dashboards. If you have experience with camping, you will be familiar with how fierce the summer weather sometimes can be. The awning of your caravan needs to be water repellent - this also applies to your raincoat - to sustain the heavy rainfall now and then. To make fabrics and textiles hydrophobic, Empa - a research institute of the ETH Domain, applies plasma polymerisation to deposit thin, nanoscale layers on top of fabrics and fibers. For this, they are using a Controlled Evaporation and Mixing system, in short a CEM system. In one of our previous blogs ‘Hydrophobic coating, the answer to exercising in the rain’ you can read about this application.
Mass flow controllers are used to make awnings hydrophobic
Bronkhorst is also involved with many smaller attributes you will encounter on a campingsite. Most people still enjoy the comfort of gas for heating or cooking on the stove. But also with gas we are able to fire up the barbecue in no time at all, in comparison with the old-fashioned briquettes that are sometimes hard to ignite. When gas escapes from a pressurized cylinder, you’ll recognize this from its penetrating scent. However, like Sandra Wassink stated in her blog “How mass flow controllers make our gas smell”, natural gas is odorless. By controlled supply of odorants like Tetrahydrothiophene (THT) or Mecaptan with a mass flow controller, the scent is added to the natural gas on purpose.
Let’s stay with the topic scent for a moment. For when we want to decrease the amount of mosquitos in our surroundings, we often enlight a citronella candle when we are getting tired of using the flyswatter. With the CORI-FILL dosing technology, Bronkhorst offers an easy-to-use setup to dose fragrances, like citronella, in candles. The addition of fragrance to a candle should be carefully monitored to ensure the candle burns cleanly and safely. To read in more detail about the production of scented candles, please read the blog of Graham Todd.
However a candle can bring much light to your surroundings, you won’t take a candle with you when you haste to the camping toilets at night. Instead you will use a flashlight of course. The working principle of the LED (Light Emitting Diode) inside this flashlight is a technology where Bronkhorst plays its part. LED works via the phenomenon called electroluminescence, which is the emission of light from a semiconductor (diode) under the influence of an electric field. By applying a semiconducting material like Gallium arsenide phosphide for instance, the manufacturing of red, orange and yellow light emitting diodes is possible.
I already told you so much, but frankly, just a tiny bit of all the camping applications we are involved at. Hopefully you got some more insights on the importance of Bronkhorst in many industries, also when you go camping.
If you want more information concerning the discussed applications, please contact us.
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The Tour de France has started last week, and all cyclists have prepared for this particular event for months. But, did you ever thought about how flow measurement could be of influence on the cyclists’ performance? Here’s how……
A while ago I had the chance to visit Relitech in Nijkerk. A company that is specialized in the development and design of reliable healthcare solutions. I talked to both Directors Ivar Donker and Henk van Middendorp about the activities of Relitech in the medical industry and their Metabolic Simulator. With all their enthusiasm and dedication in their line of work, I came to new insights regarding their matter and the importance of a company like Relitech.
In sports it’s all about optimal performance. Athletes are forced to push boundaries and the devil is in the details, more than ever. A few hundreds of a second can make a huge difference in - for example - a gold medal race. So testing the athletes’ condition and endurance is an important part in the bigger picture of their performances. This can help them to train more efficiently and it provides information that can be used for maybe a change in for example, the athlete’s diet. For metabolic measuring, a lung function device could be used and these systems often easily interfaced with ECG’s, bikes and other external devices for complete, integrated cardiopulmonary exercise testing.
The big question is how to get the best performance by meeting legal regulations? Validation is the magic word. And for that, Relitech developed a metabolic simulator. Let’s take a look at some of the technical details of a device like that.
Metabolic simulator: quality control for respiratory products
In order to keep a high performance of respiratory products like lung function devices, they need to be validated, to meet the demands of legal regulations as well. The current situation in quality control regarding devices like these, is that it’s limited due to the fact that each sensor (O2, CO2 and flow) is calibrated separately, disregarding the critical dynamic interaction between each sensor. Relitech therefore came up with an in-field solution for their customers by developing this metabolic simulator.
Thermal mass flow controller
As we’re getting closer to the answer on the question I asked at the very beginning of this blog, we need to dig a little deeper into the Relitech simulator. First of all it’s fully mobile, which means it’s easy to transport and secondly it is ideal for on-site testing (in for example a lung function device used for athletes). The simulator mixes pure nitrogen and carbon dioxide by using two Bronkhorst thermal mass flow controllers. By mixing those two gases you can generate breathing gas exchange patterns, real-time and extremely close to authentic human breathing patterns. The results are so-called capnographs that resemble the ones of for example, athletes. On the readout display of the Metabolic Simulator the capnograph values are visible. V’CO2 represents the exhaled amount of carbon dioxide and V’O2 is the amount of oxygen inhaled. BF is simply an abbreviation for breathing frequency.
“Using mass flow controllers is not new to me…” Van Middendorp explains, “…as I was already involved in designing lung function systems long before I joined Relitech in 2002.”
“As we started developing the metabolic simulator here at Relitech, we were looking for compact and highly accurate mass flow controllers and that’s where Bronkhorst and I crossed paths. So partly by using these compact thermal flow controllers we were able to develop an even more compact simulator design.”
Relitech, reliable technology
With dedication and passion Relitech develops reliable technology by focusing on electronics, software and embedded software. In combination with consultancy regarding measurement technology, their core competence lies within the medical sector, such as lung function measurement, anaesthesia and hyperthermia applications. For this, the company is ISO13485 certified. By working closely with various universities and academical institutes, multinationals and small businesses they have built an impressive and very diverse customer portfolio.
Ready for the Tour de France
So, for all the athletes out there, it’s time to put on the finishing touches and get ready for 2018. Who do you think will win the Tour?
Check out the application story of quality control for respiratory products.
As a researcher at the PC2A laboratory, I deal with low flows on a daily base. The PC2A laboratory (PhysicoChimie des Processus de Combustion et de l’Atmosphère) is a multidisciplinary public research unit (CNRS/University of Lille), whose activities concern the characterization of the atmosphere and combustion physico-chemistry. Physico-chemistry in general is chemistry that deals with the physicochemical properties of substances. Bronkhorst instruments play an essential role in our researches, for measuring and controlling these substances in various researches. In this blog I will provide an explanation of our research and why we need mass flow control.
Research activities of the PC2A laboratory
Research activities of the PC2A laboratory are related to energy and environment and are conducted by approximately sixty people divided into three research teams with their own disciplines:
1. Physical Chemistry of Combustion
Our first research team is working on the physico-chemistry of combustion. The initial goal of this research is to understand combustion chemistry, for instance how are formed pollutants such as Nitrogen Oxides ( NOx) and soot in flames. We develop detailed kinetic mechanisms of the oxidation and auto-ignition of substances, such as: biofuels, hydrogen, synthetic fuels, biomass or coal. All thanks to our large experimental platform containing flames, rapid compression machine and laser diagnostics techniques.
2. Physical Chemistry of Atmosphere
In the research team ‘Physical chemistry of the atmosphere’, we study chemical kinetics of reactions of atmospheric interest. The two main topics for us within this discipline are:
- Homogeneous and heterogeneous reactivity in the atmosphere to understand the transformation of pollutant gases and particles (pollens, soot) in the atmosphere;
- Air quality with experimental characterization and numerical simulation of indoor and outdoor environments, pollution sources and impacts on health and climate.
For these experiments we develop laboratory instruments to characterize the reactivity of important species that are involved in the atmospheric chemistry processes, especially reactive species (radicals). To perform our experiments it is essential to know precisely the amount of gas that is offered to our laboratory reactors and then the concentration of the reactants in the chemical system. For this application we use Bronkhorst mass flow controllers, the EL-FLOW Select series. These instruments allow us to easily perform parametric studies because of their fast response and high repeatability. Moreover, consistency in flow is crucial for accurate measurement.
3. Nuclear Safety: Chemical kinetics, Combustion, Reactivity
Our third team is a collaborative team between the PC2A and the Pôle de Sûreté Nucléaire (PSN) of IRSN (Institut de Radioprotection et de Sûreté Nucléaire), working on issues in relation to thermodynamic and chemical reactivity of fission products. The main objective of this research is to validate the estimations of radio-contaminant products emissions in case of nuclear accident by modeling development and experimental studies.
Mass flow controllers for physico-chemistry
The PC2A laboratory uses multiple mass flow controllers of Bronkhorst. And this is not only for their specifications like a fast response and high repeatability. Also because of the easy operation of these mass flow controllers with the Labview software these instruments are ready to hand. The possibility to export data and moreover the flexibility with switching between different flow controllers, make Bronkhorst a perfect match for us. The flow instruments we use in the lab are the thermal mass flow controllers (EL-FLOW Select series) and the flow controllers with a low pressure drop ( LOW-dP-FLOW instruments).
Watch the video of the working principle of EL-FLOW select.
To learn more about the LOW-dP-FLOW, please consult the product page.
For most people the classic summer treat is ice cream. Around 7 billion gallons of ice cream and other related frozen desserts are produced every year worldwide, with production peaking (as you might expect) in the summer months, according to the International Dairy Foods Association. Yet, the moment you consume an ice cream, you will probably not wonder how this delicacy is being made. To get that perfect ice cream, a mass flow controller is often used.
What does ice cream have to do with mass flow meters?
Ice cream contains many different ingredients, such as fat, sugar, milk solids, an emulsifying agent, flavouring and sometimes colouring agents. But there is one main ingredient that you may not have thought about, probably because you can’t see it—air. Ice cream is made by freezing and simultaneously blending air into the ingredients. So why is air so important?
If you have ever had a bowl of ice cream melt, and then refroze it and tried to eat it later, it probably did not taste very good. Moreover, if you leave a carton of ice cream out in the hot sun and let it melt, the volume of the ice cream would simply go down. Air makes up anywhere from 30% to 50% of the total volume of ice cream, therefore, aeration in the production process is crucial.
The amount of air in ice cream (often called overrun) affects the taste, texture and appearance of the finished product. Higher aeration will produce a tastier and smoother ice cream. A side effect of adding air to ice cream is that it tends to melt more quickly . Thus, for attaining an optimal structure of the ice cream, it is important to have a stable inlet air flow in the production process with a constant cream/air ratio. This can be achieved by using a mass flow controller.
The process of whipping ice cream into shape
To guarantee the right consistency and structure which ensures a full flavoured ice cream, the cream must contain the correct proportion and composition of air bubbles. Hence, aeration mixer manufacturers use a mass flow controller to dose an exact amount of air into the cooled mixer. Such a mass flow controller will ensure a continuous air delivery, proportional to the cream flow . The mass flow controller must be capable of maintaining its performance regardless of any possible back pressure variation. Occasionally, a check valve is mounted downstream of the mass flow controller. If inlet pressure drops, such valve will avoid ice back stream into the instrument. A pressure meter is also used with the purpose of monitoring the inlet pressure.
The SEM (Scanning Electron Microscope) picture below shows the ice cream microstructure. Air bubbles are a critical ingredient. Experts claim its optimal size, distribution and quantity are one of the secrets for having a creamy texture recipe. Hence, according to meet such demands, Bronkhorst has provided efficient solutions for enhancing continuous aeration processes.
So, the next time you head to the ice cream parlor with your friends, be sure to keep in mind the importance of Bronkhorst when it comes to that delicious refreshment.
- Watch the video about the EL-FLOW Select to learn more about the thermal mass flow instrument which can help you create ice cream.
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