James Walton
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Anglian Water Services cleans water to the highest standard, delivers it to millions of homes, and carefully manages it to ensure it never runs out in an area of the UK. They started a project to optimize and further control dosing of phosphates in the public water system.

The functionality of orthophosphoric acid in the public water system

Public water systems commonly add phosphates to the drinking water as a corrosion inhibitor to prevent the leaching of lead and copper from pipes and fixtures. Inorganic phosphates (e.g. phosphoric acid, zinc phosphate, and sodium phosphate) are added to the water to create orthophosphate, which forms a protective coating of insoluble mineral scale on the inside of service lines and household plumbing. The coating serves as a liner that keeps corrosion elements in water from dissolving some of the metal in the drinking water. As a result, lead and copper levels in the water will remain low and within the norms to protect the public health..

What was the original process ?

In the original process a down-steam analyser was in-place to measure the concentration of orthophosphoric acid in the main flow. The measurement results were checked against the required concentration and used to adjust the pump speed and therefore the level of orthophosphoric acid in the main flow. With this process Anglian Water Services can secure copper and lead concentration levels in the water acceptable to protect the public health. Nevertheless the process had room for improvement, which will be discussed in this blog.

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The original process of record

What are the limitations in the original process?

The reactive feed-back loop mechanism for dosing phosphates was not a preferred working method. We could not react quickly enough to the changing main flow to reduce or increase the dose proportionally. We had to ensure that we dosed to a level meeting the legal requirements assuming the station was processing maximum flow. Secondary costs were added to the system by needing double redundancy on the analyser to ensure there is no break in the measurement of orthophosphoric acid levels.

Project objectives

  • Reducing phosphate levels.
  • Reducing the cost of meeting legal environmental standards for the business.
  • Remove the downstream analyser and redundant spare in the process of record.

Two sensor technologies were evaluated to enhance the process ; Differential Pressure and Coriolis technology. The Differential Pressure instrument was the most cost effective and allowed us to meter the Orthophosphoric acid flow as a volume, it would take an analogue signal input and adjust the dose proportionally to the main flow.
The Coriolis Mass Flow Meter utilizes direct Mass Flow Measurement, which is preferable over volume flow for this application and is more accurate and repeatable, but is more expensive. It would also take an analogue signal input and adjust the dose proportionally to the main flow.

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Combination of mini CORI-FLOW with Tuthill pump

Making a decision appeared to be based around return on investment. Essentially the time taken to generate sufficient savings. However, during the demonstration of the Coriolis Mass Flow Meter we learned something new that would change the direction of our final design. The Coriolis Mass Flow Meter gave the density of the fluid being metered as an output.

Why was this important?

Phosphoric acid it sold in diluted concentrations , usually 80% in solution. What we have found is that there is a variation in the actual concentration at the point of use.

At this point we already knew that either the Differential pressure or Coriolis technology could support us to enhance the process of record. Now we had the chance to go to the next level and take a previously unavailable but very important parameter and use it to really refine the dose ratio.

The extra density parameter available with the Coriolis Mass Flow Meter made the decision for us. Dosing would now be controlled proportionally to the main flow and the density/quality of the phosphoric acid being used.

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The enhanced process

What are the projected benefits using Mass Flow Meters:

As we look to go live on the first five installations of this technology, we are projecting the following:

  • Stable concentration of orthophosphoric acid in the public water system.
  • Maintaining the public health commitments of the Water Industry.
  • Decreasing the addition of phosphoric acid into the environment by significant levels.
  • Two-fold cost reductions: by eliminating the down-stream analysers and the consumption of phosphoric acid.

At Anglian Water Services they live with a Love Every Drop approach. The Love Every Drop approach is a vision for how they believe a modern utilities company should be run. That vision means creating a country with a resilient environment that enables sustainable growth and can cope with the pressures of climate change. Creating infrastructure that is affordable and reliable, meeting the needs of customers, communities and the environment. We want our people and our communities to be resilient too. Phosphoric acid is connected with the concept of planetary boundaries according to Rockström et al. 2009. Anglian Water Services was able to reduce the consumption of phosphoric acid in their processes without sacrificing the quality of the water. This fits with the way they run their business.

Our water treatment specialist are more than happy to help you face your challenges in water treatment. Send us your questions

Contact our Water Treatment Specialists

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Ferdinand Luimes
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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).

resonance

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
  • pigtails

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.

Coriolis dosing block

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.

Mandy Westhoff
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A direct translation of the word ‘accreditation’ is providing trust. To measure this form of trust, standards are made to measure the expertise, impartiality and the level of continuous improvement of an organization. Laboratories that are accredited to the international standard ISO/IEC 17025:2005 have demonstrated that they are technically competent and able to produce precise and accurate test and/or calibration data.

Why are precise and accurate measurements important? For an example: If you pay the bill at the fuel station you trust that the amount you have to pay is an accurate equivalent of the amount of fuel which you filled-up. The same counts for many additional processes in which measurement equipment are used to secure the outcome of your process. An ISO/IEC 17025:2005 test certificate is the highest international level of calibration security which can be provided for measurement equipment. Bronkhorst is a proud owner of an accredited in-house ISO/IEC 17025:2005 Calibration Centre (BCC).

In this week’s blog I would like to take you with me to get a glance at our Bronkhorst Calibration Centre (BCC). This has been accredited since 2010 for gas, pressure and liquid flow calibration services.

For this, I followed Mandy Westhoff, one of our calibration centre operators, during her daily routines to get a realistic view on the activities of the calibration centre.

Why do flow meters have to be calibrated?

In general, all flow meters will be calibrated as a final step in production. The instrument with certain parameters will be compared with a fixed reference in certain environmental conditions, to provide real flow measurements.

Measuring equipment is used to secure the outcome of a process, process owners have to be able to rely on these measurements where high accuracy and – more and more – traceability play an important role, for example in the Pharmaceutical market. It is a way of risk management.

Throughout the years, we have noticed a distinctive increase in ISO/IEC17025:2005 calibrations in our calibration centre. An ISO/IEC 17025 calibration is often required as this is the highest level of calibration available in the market.

What kind of calibrations can be done in the calibration centre?

The Bronkhorst Calibration Centre is an independent department within the Bronkhorst organization and therefore not subjected to any commercial influences whatsoever.

It can be said that the tasks of the calibration centre are twofold:

  • The BCC acts as an in-house lab which maintains all calibration standards used within the Bronkhorst organisation.
  • The BCC acts as an external calibration lab which performs ISO/IEC 17025:2005 calibrations for anyone who wants this certification on their instruments, for both Bronkhorst instruments and other brands. Moreover, the BCC can perform adjustments on new and existing flow meters and controllers and calibration devices.

The Bronkhorst Calibration Centre, an external calibration lab

The scope of the calibration centre includes calibration of gas flow, liquid flow and pressure.

About 60-70% of the performed ISO/IEC 17025:2005 calibrations are ‘as found’ calibrations on used instruments. Many of our customers, especially in the Pharmaceutical market, Universities and Automotive industry, will send their instruments once a year for calibration. So they have a reliable instrument calibrated according to the highest level of calibration security which they can use as a reference for their own calibrations on-site.

To offer the highest standard of precise and accurate test and/or calibration data the environment of the laboratory is fully controlled. The calibration will be executed in a high-tech lab under conditioned circumstances by 21°C ± 2°C and a humidity of 50 ± 20%, which is outstanding. Even sunlight through the windows has been avoided and movement of people has been minimised as much as possible. Non-authorized personnel is not allowed to enter the calibration centre.

Bronkhorst calibration centre

Can you explain the calibration process in the calibration centre?

After the acclimatisation process and setup, the operator will conduct a leakage test using the Flowbus Piston Prover (FPP). This test will be done prior to every calibration as a security check to maintain the high level of quality assurance.

After approval of the environmental conditions, the calibration starts. A standard calibration is performed on several measurement points. On these measuring points the accuracy of the instrument will be determined.

After a successful calibration the instrument is provided with a label mentioning the date of calibration and certificate number, so all can be traced back to the calibration dossier. The BCC coordinator will check if everything is done by protocol and all ISO/IEC 17025:2005 calibration dossiers will be sent to the BCC Officer to perform a final check.

How about training?

All our calibration operators are trained to perform gas, as well as pressure and liquid calibrations according to the ISO/IEC17025:2005 standard. Furthermore, we are taught how to maintain calibration devices, such as cleaning glass tubes and the chemicals which are used for calibration procedures.

Is it dangerous to do this type of work?

Training is the most important part. All our operators are highly competent and skilled employees. But still, all activities are primarily centered on human work. To keep the risk level as low as possible, everything is monitored closely during the calibration process and all materials used are checked on a regular base.

What makes your job interesting?

You never have a dull moment in this job, every day is different. The service you provide is always different, because it is customer specific. It is a nice idea that you can contribute to a successful customer’s process.

certificate Bronkhorst Calibration Centre

Gerhard Bauhuis
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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.

Surface treatment

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.

Coating of a dashboard 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.

Glass coating

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.

Hydrophobic coating

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 Mass flow controllers are used to make awnings hydrophobic

Odoration

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.

Barbecue

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.

LED lighting

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.

Flashlight

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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Johan van 't Leven
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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.

Relitech Directors

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.

Cardiopulmonary Exercise Test

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.

Relitech 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.

Relitech

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.

Frank Doornbos
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The first variable area (VA) meter with rotating float was invented by Karl Kueppers in Aachen in 1908. The device was patented in Germany that same year. Felix Meyer was among the first to recognize the significance of Kueppers’ work and implemented the process for offering the meter for sale. In 1909, the firm of "Deutsche Rotawerke GmbH" was created in Aachen (Germany). They improved this invention with new shapes of the float and of the glass tube. It didn’t take long for the new device to capture attention in Europe, the United Kingdom, and other areas.

VA flow meters (or purge meters)

Over time, different types of VA flow meters (also called purge meters) have been developed, usually in response to some specific need. Nowadays a purge meter usually consists of a tapered tube, typically made of glass or plastic. Inside this tapered tube there is the ‘float’ which is made either from anodized aluminum or ceramic. The float is actually a shaped weight that is pushed up by the drag force of the flow and pulled down by gravity. The drag force for a given fluid and float cross section is a function of flow speed squared only.

While the meters are still relatively simplistic in design, relatively low cost, low maintenance and easy to install they are used in many kinds of application. Despite these facts, the traditional VA meter has a number of drawbacks. For instance, graduations on a given purge meter will only be accurate for a given substance at a given temperature and pressure. Either way, due to the direct flow indication, the resolution is relatively poor. Especially when they are built into a machine, reading might be hard. Moreover, the float must be read through the flowing medium, so you can imagine that some fluids may obscure the reading.

9 reasons why to use a thermal mass flow meter instead of a traditional purge meter

As for the current century, Bronkhorst has developed a thermal mass flow meter series (MASS-VIEW, as shown in picture 1) which is the digital high-tech alternative to the traditional VA flow meters. Thanks to today’s digital possibilities, many other advantages arise for many industrial processes and chemical plants.

bronkhorst-mass-view-flow-meter MASS-VIEW flow meter in application

  1. The MASS-VIEW flow meter series operate on the principle of direct thermal mass flow measurement (no by-pass); rather than measuring the volume flow it measures the actual mass flow, without the need of temperature and pressure correction.
  2. The digital OLED display provides an easy direct or relative reading of the actual flow. Herewith parallax errors are excluded.
  3. With this digital mass flow meter it is easily possible to obtain the accumulated flow. This availability of data gives insight in costs, leading to data driven decision making power.
  4. In contrast to the traditional VA meter which need to be mounted in a vertical position, this digital alternative can be mounted in any position.
  5. The flow path is made of sustainable aluminum rather than plastic or glass which is fragile.
  6. The instruments are standard equipped with 0-5V, RS-232 and Modbus-RTU output signals. Note that the traditional VA meters usually do not have any output signal available at all.
  7. As a standard feature, there are 2 built-in relays which indicate an alarm situation. Herewith, external devices can be controlled.
  8. Multi Gas; as opposed to traditional VA meters, which are produced for one particular fluid only, the digital alternative has up to 10 pre-installed gases available as a standard feature.
  9. Multi Range; traditional VA meters usually have a rangeability of 1:10 and one single full scale range only, the digital alternative has a rangeability of 1:100 as well as up to 4 pre-installed flow ranges.

Achieve a stable flow

A VA meter, whether it is a conventional or a digital one, can be equipped with a built-in needle valve. This needle valve enables the user to regulate the flow rate by means of a restriction inside the flow channel. As long as the inlet pressure is stable, the subsequent flow will be stable too. On the other hand, once pressure conditions are susceptible to change, the flow rate will become equally unstable. If this is not desirable, you’ll have to compensate these pressure fluctuations.

Flow control

Manual control valve

This effect can be eliminated by using a manual control valve like the FLOW-CONTROL series which keeps the pressure drop across the needle valve (delta-P) constant. This is accomplished by a second (normally open) valve, though it is operated by a membrane this time. The operating principle is based on a balance that forms between the pre-pressure, back-pressure and the spring force on the mebrane. A change in the pressure conditions leads to a change of the equilibrium and thus a change in the valve position as well (as shown in the picture below).

working-principle-control-valve Working principle of a pressure compensated control valve

Although Bronkhorsts’ pressure compensation technology is suitable for either gases and liquids, the nice thing about this is that both technologies, the digital VA meters and pressure compensation, lend themselves well to being built together. However, in that case it is applicable for gases only.

Learn more about the different models in the manual constant-flow control series