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Choosing a Solids Flow Meter - When is testing is needed?

Not all Solids Mass Flow Meters are created equally, so how do you know which meter is best suited to measure your product??? When asking this question, the best answer is, when in doubt, test some product!  Most manufacturers of mass flow meters should have a test lab and a list of products that they have tested with their devices, building a database of what works and what does not work.

WHAT TO LOOK FOR WHEN EXPLORING

THE TESTING OPTION?

REPLICATE THE INSTALLATION - Testing a product sample should also be done in a way that replicates the application or installation location.  This means that the equipment being used for testing should be similar to that of what will be used in the field.  For example, if the application calls for a flow meter (flowmeter) to be installed under the discharge of a screw conveyor, then the testing lab should have a screw conveyor.

Simulation of Screw Conveyor Feeding a CentriFlow Type II Meter

Simulation of Belt Feeding a CentriFlow LDM Meter

REPLICATE THE APPLICATION PARAMETERS - The testing lab should test the product such that it will be in the field, meaning that if the product temperature is elevated or cooled, then there should be some way to simulate that in the test lab.  The flow rate or a mathematical equivalent of that flow rate should be used as well.  This way the best simulation of the actual application or installation is replicated.  Nothing is worse than getting a test done in the lab, only to find out that since it was not replicated to the field parameters, that the meter will not work correctly after it has been installed.

Replication of Flow Rate through CentriFlow Meter

PREPARE A TEST REPORT - The testing lab should provide a completed test report, noting how the test was completed, the product tested, the equipment used, and showing the results of the test.  The goal of testing is finding out if the flow meter is the right piece of equipment for the product, so the test report should reflect this and should be able to be used to replicate the testing.

Sample Material Test Report for Corn Germ in a CentriFlow Type II Meter

THE LITTLE EXTRAS - With plant personnel being so busy these days, the test lab should be able to provide those little extras that today's technology provides.  For example, since it is difficult to be able to visit a manufacturer's site to see a test first hand, the test lab should provide a downloadable link to a video of the testing or be able to use some online meeting software to provide a window to the testing.

Test Video of Corn Starch in a CentriFlow Solids Mass Flow Meter

When looking at the testing option, the first place to look is the website of the manufacturer to see if they have a list or database of tested products.  The more products tested, the more they will know about different product characteristics and therefore the more they know about how their flow meter will perform.  Videos, test reports, and general product knowledge are all keys to a successful installation of a solids flow meter.

Product Test Videos using the CentriFlow Solids Mass Flow Meter

Applications by Industry using the CentriFlow Solids Mass Flow Meter

Example - Cement/Concrete Industry - Test Reports using the CentriFlow Solids Mass Flow Meter

For more information about the Product Testing Capabilities, Material Test Reports, Product Test Videos, or the CentriFlow Solids Mass Flow Meter, visit our site at easterninstruments.com, call us at 910-392-2490, or email us at sales@easterninstruments.com today!

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Measuring Mass Flow of Air in a Duct with a Multivariable Transmitter

When measuring the mass flow of air flow in a duct or pipe, using the correct flow element is half the battle.  After deciding that using a differential pressure device like a Velocity Averaging Pitot is the right way to go, getting the correct instrumentation to measure that differential pressure is not something that every transmitter can do.

VAP³ Velocity Averaging Pitot

In typical industrial, combustion, and power generation applications, the differential pressure to be measured ranges from a high of 8 to 10 inches of water column down to 0.25 inch of water column or even less.  Getting a transmitter that can measure these ranges and have a turndown that can measure the low end accurately usually requires getting a laboratory type of transmitter, rather than an industrial differential pressure transmitter.  These are typically not satisfactory for these types of applications, so most users go with an industrial transmitter that has a very large URL (upper range limit).  This is not by design or desire, but typical industrial transmitters have an upper range of 25 inches of water column or even 40-50 inches of water column!  To ensure that they can measure the maximum differential, they will have these transmitters scaled down, making their accuracy at these lower range or draft range differential pressures very poor.

To complicate the challenge, to get an accurate mass flow measurement, measuring the temperature and static or absolute pressure is required so as to compute the density of the air.  Without getting separate instruments for each of these variables, which can be very costly, most users get a multivariable transmitter.  Most industrial multivariable pressure transmitters not only have a very high URL for the differential pressure, but also do for the static or absolute pressure.  They are designed to be used in the widest possible array of applications, instead of being dedicated to the ranges needed for most industrial, combustion, and power generation applications. On top of the high upper range on the sensors, these devices are over complicated, and require expensive software to be setup and configured.  Again, since they are used for a wide array of applications.  They also typically have a diaphragm seal, which protects the sensors from contaminants and condensation in the impulse lines.  This is great for dealing with corrosive environments and dangerous gases, but for typical air flow measurement in a duct, the diaphragm seal only complicates these transmitters and adversely affects their turndown and accuracy. So, the question remains, how do you get an accurate differential measurement on low end pressures, get a computed density from live variables, and have a simplified interface while providing the mass flow??

Finally the answer has arrived!

The QVT Mulivariable Transmitter

QVT Multivariable Transmitter

The QVT is a loop powdered microprocessor based multivariable smart transmitter, which simultaneously measure the differential pressure, absolute pressure, and temperature.  It provides a live density computation and mass flow rate computation, which is compensated for the density it calculated.  It is designed to be used specifically in these types of low differential pressure applications, have a typical URL of 8 inches of water column, while being able to be set to a full scale of 0.8 inches of water column.

The unit has a sealed sensor head connected to a cast aluminum industrial enclosure, making it perfect for industrial locations.  The device can be configured with a 3 or 5 port manifold and a Transmitter Mounted Purge, which is a low volume continuous purge.

Coupled with the VAP³ Insertion Probes, Ducted Section (DSV) unit, or High Beta (HBP or HBE) unit, a complete flow measurement solution is now available for industrial, combustion, or power generation applications.

For more information, check out our website easterninstruments.com, call us at 910-392-2490, or email us at sales@easterninstruments.com today!

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Air Flow Straightener, Air Flow Profiler, and Air Flow Conditioner - What is the difference?

When measuring the flow of air or gas in a duct or pipe, accuracy is dependent on the type of device used to make the measurement, but is very dependent on the flow profile in the duct or pipe.  For example, if the flow in the duct or pipe is turbulent, many types of flow measurement devices will not even be able to measure the flow or have such an error you would be better off not having the measurement at all.  Here we will look further into turbulence and ways to minimize or eliminate it so that an accurate air flow measurement can be made. What is Turbulence? Turbulence can come in many forms, for example the flow could be spinning in the duct (cyclonic flow), or the flow could be going in the opposite direction than it is supposed to be going (reverse flow), or it can be off to one side or even angular (not parallel to the center-line of the duct or pipe).  When a flow sensor, averaging pitot tube, thermal mass sensor (thermal dispersion), venturi, or even an orifice plate is used in flow conditions that are turbulent, the devices cannot possibly perform as designed, because the design of these types of air or gas flow measurement devices requires the flow to be uniform or "laminar".  Uniform or Laminar Flow is when the flow is parallel to the center-line of the duct and the velocity is equal across the cross-section of the duct.  This is the "perfect world". So what causes turbulence in a duct or pipe? Turbulence is caused by changes in the duct shape, obstructions, or other pieces of equipment.  A simple change in the duct like a bend will cause the flow to change its profile.  For instance, right after a 90 degree bend, the flow will impact the outer radius, start to spin, and hug the outer wall.  When the duct configuration calls for a tee or take-off, the flow profile will change because some of the flow will want to not change direction and some will have to change direct, which will cause some of the flow to even reverse direction, creating pockets of very turbulent flow.  In large ducts where the duct wall must be stiffened or supported by structural steel, the flow around these support will change the flow profile and create turbulence right after the obstruction.  Some of the worst turbulence is caused by modulating dampers in a duct.  As the damper is adjusted, the flow profile is changed significantly and will worsen as the damper's louvers or blade is closed.  And then there is the flow on the outlet of a fan, don't get me started on discussing turbulence at this point in a process.

Typical Flow Turbulence After a Bend

Typical Flow Turbulence Caused by a Tee or Duct Take-off

Typical Flow Turbulence Caused by Internal Duct Obstructions

Typical Flow Turbulence Caused by a Louvre Damper

So now that we have a better idea of what turbulence is and where it might be located, it is easy to see why putting a flow measurement sensor in a turbulent area will cause inaccuracy.  The big question now, is what to do about it?  The best solution is to put the sensor where there is no turbulence, but this may require many lengths of straight runs in order to get the flow profile to return to a Uniform or Laminar state.

The Old Standby Solution - Perf Plate or Honeycomb Flow Straighteners

For years the only solution when the straight runs were not available, which is the case in larger diameter ducts, was to use a flow straightener like a perf plate or honeycomb.  The Straighteners job was to do just that, straighten out the flow pattern.  The way this is done was to restrict the flow in the duct in a way to force it through much smaller openings.  These can be holes in a plate or actual fins or restricting sections made from thin metal.  The major drawback from this straightener is that in order to really straighten the flow, these must be relatively small openings, so there is a lot of resistance to flow that is created.  This resistance to flow causes back pressure that can affect the ability of the system to maintain the desired flow.  Unrecoverable loss of the pressure will result in dramatic changes in the overall system.  The other thing is that these devices will not fix issues where the flow is reversing or where it is not equal across the cross section of the duct.  Flow hugging the outer wall will still continue to hug the outer wall, but may actually begin to reverse since all that flow is being forces through the small openings.  The devices are also not very robust devices, and can easily break or become plugged.  Typically a flow measurement sensor is placed after the straightener, trying to take advantage of any flow straightening that occurs.

The Next Best Thing - Nozzles and Venturi Flow Profilers

The flow nozzle or venturi devices would be the next best thing to the flow straightener, having a section where the diameter of the duct is restricted down or nozzled down to a smaller diameter.  This nozzling affect forces the flow to speed up through the smaller section, relieving issues like reverse flow and uneven flow across the duct cross section.  The draw back to these devices is that the ratio of the duct area to the area of the reduced section is very high.  This ratio is known as the beta ratio.  With these types of beta ratio devices however, cyclonic or spinning flow is not corrected and the large change in diameter is done over a short length making an abrupt change in the flow pattern.  This type of device also has a very large unrecoverable pressure loss potential, so recovery sections are usually used to try to reduce this pressure loss.  However, this section requires a very large length of duct.  Typically there are pressure taps on the inlet and throat section after the diameter change, where the differential pressure is measured to provide the flow measurement.

The Best Solution is Here!  The High Beta from Eastern Instruments

The best solution would be a flow conditioner that eliminates cyclonic flow, elminates reverse flow, profiles the flow evenly across the duct, and does not require a large length of duct or create back pressure and large unrecoverable pressure loss.  The High Beta from Eastern Instruments is exactly that device!  Its converging section with integral straightening vanes lead to a section of duct with our VAP³ Velocity Averaging Pitot Tubes, where a Uniform or Laminar Flow is created with almost no required upstream straight duct runs.  The turbulent flow is directed through the converging section where the straightening vanes break up flow issues, while not restricting the flow causing back pressure.  The straightening vanes are a structural part of the device, so they are very robust and will not break off in the flow stream.  The smaller diameter duct section, call the throat, is designed such that the beta ratio is moderate, much higher than the venturi, allowing the flow to be conditioned without causing a high unrecoverable pressure loss, and no recovery section is required!

The High Beta Process Flow Element comes in low pressure and high pressure models in various standard diameters.  The external spool or duct sections can be painted carbon steel or stainless steel depending on the requirements of the application.  The integral VAP³ Pitots measure this conditioned flow with unparalleled accuracy.

High Beta Process Flow Element (HBP)

For large ducts, square/rectangular duct and Combustion applications, the High Beta Engineered Flow Element can be manufactured to fit the exact needs of the customer and application.  It can be made in a wide array of configurations and materials as needed.

High Beta Engineered Flow Element (HBE)

For more information about these devices and to talk to a Sales Engineer about your application, please contact Eastern Instruments at 910-392-2490.  You can send and email to sales@easterninstruments.com if you would like to receive more information via email or visit our website at easterninstruments.com.

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Solids Flow Measurement Issues - Pulsating Flow

There are many different ways to move solid materials through a process, ranging from belt conveyors, vibratory conveyors, and pneumatic systems, to bucket conveyors/elevators and screw conveyors.  Many of these devices are great for moving the product, but if you need to measure the mass flow rate or control the flow rate, pulsations created by some of these devices can cause major problems. Devices like bucket conveyors/elevators, rotary valves, and screw conveyors have pockets, flights, or buckets that help to collect the product and move it through the device.  These create pulses or slugs of flow, some of which can be very large and there can be seconds or even moments where there is no flow at all between slugs.

Pulsating Flow through a CentriFlow Meter

Most mass flow meters require that pulsations be mechanically smoothed if at all possible, because they cannot deal with the pulsations when measuring the flow and computing the totalization.  This is typically because the device is averaging or slow in its response of measurement, so some information would be missed or misunderstood by the meter with these pulsating flows.  The product path usually has to include a long intake to the device to smooth out and present the product to the device.  This make the device take up more valuable space in the process.

CentriFlow Solids Flow Meter has a High Speed of Response to deal with Pulsating Flow

When nothing can be done to change the flow pulsations, a common practice is to electronically average the flow so that the pulsations are mitigated, providing a "smooth" flow output from the meter.  This practice can be detrimental to a control scheme, since this time averaging creates delay in the control, making the whole process suffer when changes in flow exist.  The best solution would be to have a flow meter that has a high speed of response to measure the pulsations without this delay, providing an instantaneous output signal.  If a "smoothed" or averaged flow rate is desired for display purposes, then the device should have this capability without affecting the output.

Screw Conveyor Feeding CentriFlow Type II Meter

Once such device is the CentriFlow Meter from Eastern Instruments.  The Type II is suited perfectly for installation under these types of devices.  The unit does not require a long straight run, and in most circumstances, it is recommended that the device be installed directly under the feed device, requiring only a small, short transition to the intake of the housing.  The key is the meter's fast response, being able to see flow changes every 100 milliseconds, thus providing a highly accurate flow rate and totalization regardless of the pulsations present.

CentriFlow Solids Flow Meter installation under Screw Conveyor or Rotary Valve

For more information on the CentriFlow Meter or any other product by Eastern Instruments, please visit our site easterninstruments.com, call us at 910-392-2490, or email us at sales@easterninstruments.com.

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Flow Measurement of Large Bulk Solids with a Flow Meter

When measuring the flow rate and totalization of a bulk solid materials with a flow meter, there are a lot of options.  However, when the particles of the bulk solid are large, irregular shaped, and vary greatly in bulk density, the options quickly dwindle down to a few. Large Bulk Materials like tobacco, recycled plastic bottles, recycled carpet pieces, trash, construction debris, biomass feed stocks (like wood products, hay, straw, and leaves) and the like are not only difficult to move through a process, but their product characteristics make it almost impossible to accurately measure the flow.

Biomass Materials - Hay/Straw

Biomass Materials - Wood Chunks/Chips

Recycled Plastic Bottles

Construction Debris

To get an accurate mass flow measurement of bulk solids with large particles and irregular product characteristics the mass flow meter that is used must be able to measure the flow and have no dependence on these varying product characteristics like bulk density, particle size, and product composition.  The typical device used for these types of product is a weigh belt.  However, due to the large nature of the product and bulk density variation, the weigh belt would not provide a very high degree of accuracy.  These products can have bulk densities that are very low and varying greatly when moving, making the averaging weight based measurement technique of the weigh belt inadequate.  Impact meters cannot handle these types of bulk materials either, due to the very low density, large particles, and variable density as well.  In fact some of these materials would plug the impact meter immediately.

THE CENTRIFLOW LDM METER FROM EASTERN INSTRUMENTS

LDM Meter

The CentriFlow LDM Meter has been specifically designed to handle these large particle, variable density, bulk materials.  The LDM meter uses the same mechanical design and gravimetric technology to measure these Bulk Materials.  The key is the Centripetal Force Measurement Technology behind the CentriFlow.

Principle Behind the CentriFlow Meter

The LDM Meter has a larger Measurement Pan than a standard CFM Meter, thus allowing the large particle bulk materials to pass through the meter in a similar manner, thus obtaining very high accuracy.  The meter can be installed either In-Line Flow or in Reverse Flow Orientation off a belt conveyor, giving two very simple installation options for these types of bulk materials.  The meter can also be fed from a vibratory feeder as well. For more information on the CentriFlow LDM Meter please visit our website easterninstruments.com, call us at 910-392-2490, or send us an email at sales@easterninstruments.com today!

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Check out the Technical Exclusive just published on the Powder and Bulk Solids Website and look for it in print in the near future!

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Winter Weather and how it affects Air Flow Measurement - Freezing Flow Measurement Issues

Even though it does not feel like it here in the Eastern US, it is definitely winter in many parts of the world.  And something happens every winter at process plants all around the world, namely instruments and instrumentation begin to have issues due to the temperatures, moisture, and the winds of winter.  These issues send Instrumentation Techs, Engineers, and Maintenance people scrambling to get them back online and functioning properly.

One of the biggest issues is when an instrument that is crucial to the proper operation of the a plant gives erroneous readings or stops working all together.  This is especially the case with flow measurement devices and instruments.  Having a transmitter or moisture in the differential pressure lines freeze up will cause the transmitter to stop responding or give incorrect flow measurement readings.  These can be handled sometimes (depending on the temperatures) by putting the transmitters inside a building or under a covering, protecting them from the elements, or installing a heater in the enclosure they are installed in.  The differential pressure lines or impulse lines can have a heat trace system added to them, helping to prevent moisture from freezing.  The one part of this system that normally does not get any attention is the flow element or averaging pitot tube itself.  Since they are inside the duct, they may not be accessible, or cannot be removed to be "de-iced"  while the process is running.  These devices can get winter moisture on them, and when the temperature drops, they freeze right up.  They can be coated in ice like the branches on a tree, having their pressure ports covered, blocked, or plugged up with ice.  Wouldn't it be great if these probes could have a heat trace system put on them so that they will work in the winter temperatures?? Most of the time the issue never gets resolved or the measurement is temporarily bypassed, and when warm weather returns, it is forgotten about altogether.  Then the next winter, it rears its ugly head again......

HEATED VAP³ PITOT SYSTEM from EASTERN INSTRUMENTS

HEATED PITOT SYSTEM

Well, there is a solution to this yearly issue of freezing pitot tubes, it is the Heated Pitot from Eastern Instruments!  The Heated VAP³ Pitot is not just a typical averaging pitot tube with heat trace, but a device with an Integral Heater in the actual probe!  This patented design includes an Integral Heater that traverses the length of the probe, heating from within, instead of on the outside surface.  This is an important distinction, because the metal of the probes is heated, thus keeping it from freezing AND not impeding or disturbing the flow pattern around the probe.  Applying heat trace to the outside would only heat the contacted surface AND would definitely affect the flow pattern, and thus the flow measurement.

Download the Cut Sheet Today!

The System consists of the Velocity Averaging Pitot with Integral Heater and a Control Enclosure with a Temperature Controller and Temperature Alarm Controller.  While heating the pitot material will keep it from freezing, allowing it to become overheated can damage or destroy the probe.  So, the Temperature Controller controls the temperature, while the Temperature Alarm will assist in preventing the system from allowing it to get over temperature.  This also saves money because the system will only apply power to the Integral Heater when it is needed, keeping the probes ice free when they need it!  The system controls itself, give a maintenance free solution to a yearly problem plaguing process plants.

The Heated VAP³ Pitot can be used in any application where there is a chance of freezing temperatures and moisture being present.  When ducts are large, as is the case in Inlet Air applications, multiple probes can be used, thus keeping them shorter so that the heating system works optimally, but allows a full traverse of the duct.

For more information on the Heated VAP³ Velocity Averaging Pitot Tube, please visit our website at http://easterninstruments.com, give us a call at 910-392-2490, or email us at sales@easterninstruments.com today!!

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Velocity Averaging Pitot Tubes for Air and Gas Flow Measurement

When it comes to measuring the flow rate of air or gas in a duct, there are many different devices used.  For example, there are thermal sensors, hot wire anemometers, rotating vane anemometers, static pressure drop devices (venturi, orifice plate), and differential pressure devices (pitot, annubar, primary element).  The most widely used and considered a true measurement of the flow is the differential pressure device.  The most widely used differential pressure device is a velocity averaging pitot tube.

Velocity Averaging Pitot Tube

The velocity averaging pitot tube is a device that when inserted into the air or gas flow stream, provides a high pressure measurement port and a low pressure measurement port.  The high pressure port measures the total pressure created when the air or gas stream impacts the port, where the low pressure port typically measure the static pressure in the duct.

VAP³ Velocity Averaging Pitot Tube from Eastern Instruments

The difference between the two pressures, called the dynamic pressure, can be used to calculate the flow in the duct using the Bernoulli principle and equation. This equation, in a simplified form when using a pitot tube, states that the velocity in a duct is equal to the square root of two times the differential pressure, divided by the density of the air or gas.

For the best results using a pitot tube, there should be an array of probes used to ensure that there is an adequate traversing across the duct cross-section.  In addition, the individual pitot tubes would have multiple ports, thus averaging the pressure measurement in any one probe and then in the array of probes.

Velocity Averaging Pitot Tubes in a Round or Square/Rectangular Duct

VAP³ Pitots in an Array in a Circular Duct

VAP³ Pitots in an Array in a Square/Rectangular Duct

Not all pitot tubes are created equally.  Most are just a cylindrical tube or set of tubes that have holes in them, or some modification of the cylindrical design.  The flow profile around these tubes can be distorted and even non-repeatable, causing them to have a calibration factor or "K" factor based on flow rate or velocity of the air or gas stream.

In order to get the best result and not have an affect based on the flow around the pitot tube, the pitot tube should have a cross-section such that the flow pattern is not disturbed.  Such is the case with the VAP³ Velocity Averaging Pitot Tube from Eastern Instruments.  Its patented design allows the flow profile to run parallel around it, before combining together behind the probe.  This not only allows the probe to get an accurate differential pressure measurement, but makes the pitot velocity independent, eliminating the need for the K factor.

While velocity averaging pitots can provide a very accurate way to obtain the flow rate in a duct, they are susceptible to particulate in the air or gas stream.  Most pitots can plug when the particulate is large or if it is heavily particulate laden. The high port will plug, causing an error in the differential pressure measurement.  The typical way to combat this issue is to use a high pressure purge or blow out, but these systems can be complicated and expensive to run.  The VAP³ PA Pitot from Eastern Instruments uses that same patented design that allows it to be independent of velocity yet also provides a plug resistant configuration where the high port is not in the direct impact of the air or gas stream, thus making it plug resistant.

VAP³ Velocity Averaging Pitot in the SA (Clean Air/Gas) and the PA (Particulate Laden/Plug Resistant)

To learn more about velocity averaging pitots and the unique design of the VAP³ pitot from Eastern Instruments, visit our website at www.easterninstruments.com, give us a call at 910-392-2490, or email us at sales@easterninstruments.com.

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How to Fix your Weigh Belt Feeder without major changes to your process

Weigh Belt Feeders have been widely used for many years to measure the flow rate and totalization of solid materials in a process while providing a feed device to move materials through that process.  For some products they can be accurate enough to keep in your process and deal with their calibration issues, but for some products, they can be a maintenance nightmare and something that needs to be replaced.  However, with their large footprint and complex installation, finding a replacement feeder that fits can be a real issue. One way to deal with this maintenance issue but to still have that vital process measurement is to install a flow meter that can be installed at the end of a belt conveyor.  Since the Weigh Belt is in essence a belt conveyor, it would be used as just a material handling device and not a flow meter.  Once such a device that can fit in such a tight space is the CentriFlow Type I meter from Eastern Instruments.

CentriFlow Type I Meter

The Type I meter is designed to be fed with a horizontal feed device like a belt conveyor or vibratory conveyor.  For a belt conveyor, the meter can be positioned just at the end of the belt and the trajectory of the product flow off the belt will allow it to slide through the meter's flow surfaces, providing excellent accuracy.  The graphic below shows an example of how the meter would look installed at the end of a belt conveyor.

The Type I meter comes in multiple widths/sizes and be fit to just about any width belt, and in some cases can be mounted directly to the housing or shrouding that covers the existing Weigh Belt.  The small size and ease of installation makes the CentriFlow a great choice for fixing the measurement issues associated with the Weigh Belt.  When positioned at the end of the belt, the accuracy of the measurement is typically in the +/- 0.25% of full scale range.  It is repeatable, dependable, and requires no maintenance, so all that is left to deal with is the maintenance on the belt conveyor portion of the Weigh Belt.  In fact, if the total removal of the Weigh Belt is desired, just replacing it with a simple belt conveyor and a CentriFlow can be a very inexpensive way to solve the problem as well.

For more information on the CentriFlow Solid Mass Flow Meter please check out our website at www.easterninstruments.com/solve my problem, give a call at 910-392-2490 or email us at sales@easterninstruments.com.

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Controlling the Flow of a Solid using a Feeder with Integral PID Control Capabilities

Measuring the Mass Flow Rate of a Solid Material can be hard enough, but when a process needs a Controlled Flow Rate as well, this can be really difficult.  Controlling the Flow Rate in a process requires a PID control loop, where the input is an accurately measured flow rate and the controlling device is able to provide a fast change when an input change is noted, without overshoot or undershoot. In most industrial plants, these types of flow controls are typically done by a PLC.  These same PLC's usually take in all of the inputs of the process and compute all of the outputs to all of the devices in the process.  The loads on these PLC's can vary greatly and typically result in a long scan times that can adversely affect the PLC's ability to provide the best PID control loop.  This makes the control of the loop inaccurate, slow, and creates difficulty when trying to tune the loop to obtain the highest degree of control. The best way to get around these issues is to use a dedicated local controller that provides the PID control loop for the Flow Rate Control.  These types of dedicated local controllers can be integral to the equipment that is required for the task, having one or more microprocessors.  The advantage of using a PID Controller that is part of the equipment is that it will be dedicated to only that task, using the knowledge and expertise of the manufacturer to obtain the optimal control parameters and PID tuning, thus optimizing flow control.

THE CENTRIFEEDER w/ICV

One great example of this type of device is the CentriFeeder with Integrated Control Valve, or ICV.  This device uses the principles of measurement of the CentriFlow Meter, and combines it with the robust design of the ICV to provide both accurate Flow Rate Measurement and accurate Flow Rate Control.  The ICV is a slide gate style control valve, which uses an AC, low rpm, brushless servo and an integral linear position sensor, which provides feedback for the blade movement and location or position to within 1 part in 1000.  It is mounted directly to the measurement unit, providing a single, ready to install, Feeder unit.

THE CENTRIFEEDER ELECTRONICS

The Feeder itself is much more accurate than most on the market, but it is the dedicated PID control loop within its electronics that make the system whole.  The CentriFeeder Electronics is the heart of the Feeders capabilities, and uses integral microprocessors to compute the loop output based on the Flow Rate Measurement of the unit and the position location of the blade of the ICV.  The customer is able to interact with the system through a color touchscreen HMI,  The customer's PLC can send the Set Point (Setpoint) to the unit over a 4-20mA signal or via a communications protocol like Ethernet/IP, ProfiBus, or DeviceNet.  Additionally Flow Rate, Totalized Weight, Valve Position, Percent Open, Start and Stop, and a host of other values are available over the communications protocol.  Other features like a Plot Screen for observation and tuning, Virtual Flow Stop, and Auto Delay make the system user friendly and product friendly. For more information about the CentriFeeder w/ICV or any other products, visit our website at www.easterninstruments.com, give us a call at 910-392-2490, or email us at sales@easterninstruments.com.       

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Air Flow Measurement Accuracy within a Particulate Laden Air Stream

Measuring the Air Flow in a duct can be difficult enough when the flow profile is not free from turbulence, disturbances, cyclonic flow, and reverse flow, but add to that particulate, ash, dust, or debris in the air, and it can almost be impossible.  So, how do you get accuracy when trying to measure the Air Flow in a duct that has particulate, ash, dust, or debris in the air stream? The traditional way is to use a blast purge or blow back system that will take high pressure compressed air and blow it back through the high and low ports of the air flow pitot or flow element so that any particles, ash, dust, or debris is blown out of the ports on the probe.  This not only uses a lot of compressed air, which needs to be completely dry to work properly, but it also requires a complex system of valves in order for this to be done automatically.  If the blast purge or blow back is not done on a regular basis, and if the particulate, ash, dust, or debris level is high enough in the duct, the pitot or air flow element or probe will plug very quickly causing the measurement to be inaccurate.  An automatic system is needed to perform this purge or blow out while the system is being used to measure the flow of the air in the duct.  This adds another level of complexity since the differential pressure transmitter or multivariable transmitter signal would need to be locked out or isolated while the purge or blow out is being performed so that the system does not think that the result of sending the high pressure compressed air through the pitot or flow element is changing or so that the transmitter does not get damaged from over pressurization.  As you can see this can be a very difficult thing to do and makes the cost of measurement of an air stream with particulate much more expensive. THE VAP³ PITOT A better way to deal with this would be to use a pitot or flow element or probe that is plug resistant, not allowing the particulate, ash, dust, or debris from plugging the ports on the probe.  The VAP³ Pitot is a perfect solution to this issue.  The VAP³ probe can be configured in what is called the PA mode, thus orienting the probe so that the probe becomes resistant to plugging.

VAP³ PA Pitot from Eastern Instruments

So, how does this work?  With the probe in the PA orientation, the High Port, which is typically on the upstream end of the probe, is located on the back side or downstream end.  Having the High Port on the back side prevents the particulate, ash, dust, or debris from impacting the port, plugging it and causing the differential pressure measurement to be altered, thus making the air flow measurement inaccurate.  This patented design can be used from 1,500 ft/min to 12,500 ft/min air flow velocities, making it perfect for most duct configurations.

VAP³ Pitot

The VAP³ Pitots are an Insertion Probe style or Direct Duct Mount style using the included Insertion Ports that would be welded or connected directly to any existing ductwork.  The probes are manufactured from 6061 Aluminum (Hard Coat Anodized) or 301 Stainless Steel, and are sized to fit the duct dimensions.  An array of probes is recommended based on the duct configuration or size to obtain the highest degree of air flow measurement accuracy.

Air / Gas Flow Application Guide

For more information on the VAP³ Pitots, DSV Flow Elements, or High Beta Flow Elements, click one of links or visit our website at www.easterninstruments.com, or call us at 910-392-2490, or email at sales@easterninstruments.com.

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Solids Flow Meters and Why Every Process Should Have Them

A question that we get asked a lot is "why do I need a Solids Flow Meter?" or "how can a Solids Flow Meter help my plant or process?"  To answer these questions, we first will look at what a Solids Flow Meter is and then where/how it can be implemented.

CentriFlow Solids Mass Flow Meter from Eastern Instruments

DEFINITION OF SOLIDS FLOW METER: Solids Flow Meters can be called many things from Flow Meters, Flow Instrumentation, Process Measurement Devices, or even just Process Meters.  A Solids Flow Meter can be considered an device or point measurement, that when placed in a process, provides a window into what is going on in the process.  It is an instrument that provides vital process flow data like Flow Rate and Totalization/Totalized Weight.  This can be on a continuous process or on a batch process.  The Flow Rate would be in mass units like lb/hr, kg/hr, Ton/hr, MTon/hr, etc, and the Totalization/Totalized Weight would be in mass units like lb, kg, Ton, Mton, etc.  Most Solids Flow Meters are used to measure the Flow Rate and Totalization/Totalized Weight of dry, flowable, solid materials. (For examples of products/materials that a Solids Flow Meter can be used with, see the following link:  Visit our Website for Applications using our CentriFlow Solids Flow Meter WHERE CAN SOLIDS FLOW METERS BE USED: Instrumentation or Process Measurements can be used for optimization, making a process more efficient, can help to identify losses in a process, can provide tighter control on ratio and blending, and can provide Totalization or Totalized Weight information when filling, moving, storing, or transporting a product/material, just to name a few.  Below are a few examples of implementation of a Solids Flow Meter: Ratio Control of Additive

In this example, the customer is using the Solids Flow Meter to measure the flow of a powder coming from the screw conveyor so an additive can be applied in a mixing screw below.  Measuring the flow rate of the main product allows for a more accurate ratio control of the additive.  Without the Solids Flow Meter, the additive would be added to the flow, not knowing when the flow rate varied, wasting the valuable additive or having a blended product with an incorrect ratio.  The Solids Flow Meter's flow rate output is sent to the customer's PLC or DCS system where the setpoint for the additive is then calculated based on the desired ratio.  For even tighter control, the flow rate measurement can be used to control the speed of the screw conveyor to control the flow of the product through the Solids Flow Meter, thus providing even better ratio control. Transport of Product to Storage Silo

In this example, the customer wanted to transport their product through a pneumatic conveying system and store it in different storage silos.  The Solids Flow Meter is used to provide a Totalized Weight measurement of the product as it arrives from the pneumatic conveying system via the rotary airlock.  The product is dynamically measured and the flow is totalized, having the information sent to the customer's PLC or DCS system.  When the desired amount of total weight is measured to be stored in the first silo, the PLC switches the valve sending the product to the second silo.  This same event is repeated until all of the silos are filled with the required total weight.  The Solids Flow Meter assists the system in stopping the flow through the pneumatic conveying system when the total for all three silos is met, thus not having extra material in the transport system or under filling the third silo. The CentriFlow Meter, a Solids Flow Meter from Eastern Instruments, can be used for these types of measurements and more!  It can be configured for both Horizontal Feed devices like belt conveyors and vibratory conveyors (CentriFlow - Type I Meter), and for Vertical Feed devices like slides gates, screw conveyors, rotary valves or airlocks, bucket elevators or conveyors (CentriFlow - Type II Meter). For more information or assistance with an application or project, please visit our website www.easterninstruments.com, or email us at sales@easterninstruments.com or call at 910-392-2490!

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Measuring the Mass Flow of Difficult to Handle Powders with the CentriFlow Meter

Measuring the mass flow rate and totalization of a dry solid material can be difficult when that product is a hard to handle powder.  Product characteristics like particle size, cohesiveness, flowability, bulk density can all affect the accuracy of the mass flow measurement of a powder.  Below we will look at these characteristics in more detail and discuss how the CentriFlow Solid Mass Flow Meter is suited to deal with issues from these characteristics, making them non-issues or helping to eliminated/overcome them to get the best accuracy possible.

CentriFlow Meter - Type II Configuration

Particle Size: Particle size can become an issue when a material's particles get down to the powder regime, around 0.0394" or 1000 microns (18 mesh) and smaller.  The smaller the particle, usually the more trouble it can be to handle and therefore to measure.  However, there are definitely small particles that are not an issue, like sand, which can fall into the 0.0098" or 250 micron (60 mesh) size, but it is a very free flow granule and does not typically exhibit "powder-like" issues.  Very small particles, tend to dust greatly, can cause explosion hazards, and can build-up on surfaces, especially where the measurement is concerned. Cohesiveness: Cohesiveness is a way to describe how the product particles bind to themselves, and therefore to other materials.  Products like sand can be categorized as having no cohesiveness since you can grab a hand full of the product and it will not stick together.  Titanium Dioxide would be an example of a product that can be categorized as being very cohesive.  Grabbing a hand full of TiO2 most likely will end up with you have a ball or cake of product, with residue all over your hand.  Products like Flour, Gypsum, Limestone and others can be categorized as having slight cohesiveness and sometimes that varies from product to product. Flowability: Flowability can be described as a products ability to flow or slide off a plate when tipped at an angle.  For example, if you take sand and pile it on a metal plate, when you tilt the plate, it will most likely begin to slide off the plate when the plate is tilted at an angle of 30° to 45°.  This would be considered average flowability.  Talc or TiO2, will most likely not slide at an angle of 45°, but will need something higher.  This can be categorized a having low flowability. Carbon Black is very flowable, almost like water, and will most likely slide off the plate at an angle less than 20°.  This can be categorized as high or very free flowing.  There are a number of products that will slide off the plate at an angle less than 30° but more than 20°, and these can be categorized as above average flowability. Bulk Density: Bulk Density is the weight per volume of the bulk of material flow that a mass flow meter will see when it goes through the device.  Depending on the product, there are a number of methods for computing the bulk density ranging from just putting product into a 1 cubic foot container and weighing it (remember to tare out the container and just get the weight of the product), using a flask filled up to a specific level, or using a bulk density sampling system.  The bulk density itself is not an issue, but what becomes an issue is knowing the bulk density when the product is flowing.  Since the bulk density of a powder can change rapidly as the product is moved within a process, it is very difficult to know the "actual" bulk density of the flowing product.  These changes in bulk density often come from aeration of the product as it is moved.

Meter Construction: The CentriFlow Meter from Eastern Instruments has many features that have been designed with hard to handle powders in mind.  Standard construction of the flow paths using polished stainless steel with rounded corners helps to keep powders moving through the meter so that not only does it not plug the system, but the product presentation is optimized to get the highest accuracy.  The Type II housing is designed to contain powders, the dust created by them, and prevent plugging of clumps of cohesive products.  The internal Diverter is positioned and angled to get the maximum angle for difficult flowing products.  Many flow surface option are available which maximize slickness or reduce/eliminate sticking. VibraWeigh Option: The VibraWeigh option is an integrated vibration device that shake the Measurement Pan, helping to keep products flowing through it, while not interfering with the measurement.  This vibration is factory set to optimize the frequency and amplitude of the vibration to get the best results. Pulsed Air Option: The Pulsed Air option is a specialized air bar system that is positioned to blow off the Measurement Pan on a periodic basis.  This blast is at a high pressure, short duration, and optimum location so that most cohesive and dusty products are no match for it.  During the blast, the electronics monitors the flow meter's signal and ensures that the blast does not affect the measurement accuracy. Hazardous Locations: When the meter needs to be used to measure the flow rate of a powder that creates enough dust potential to be hazardous or explosive, options like a Purge/Pressurization System or Intrinsic Safety Barriers.  With the Purge/Pressurization System, the meter and its electronics can be located in a hazardous area by creating a pressurized loop between the components, keeping explosive dust out of the areas where electronics are contained.  With the Intrinsic Safety Barriers, the meter can be in the hazardous location, while the electronics are in an isolated safe zone.  The barriers prevent a spark from being made and igniting the dust. Testing: Eastern Instruments offers free testing of a material sample to determine the product characteristics, observe product flow in a CentriFlow Meter, and help to configuration/optimize a meter to obtain the highest accuracy.  Many product tests exist on our website Flow Watchers - Application and Test Videos Look for the items mentioned above and more by visiting our website www.easterninstruments.com, calling us at 910-392-2490, emailing sales@easterninstruments.com or by clicking on the links below: http://easterninstruments.com/products/CentriFlow/Type II Powder.html http://www.easterninstruments.com/products/centriflow/Options.html http://easterninstruments.com/services/testing.html

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Turbulence and Flow Patterns and how they affect Air Flow Measurement in a Duct

One question that I am asked about all the time is "Why would I need to have a flow straightener and/or flow conditioner to get a good air flow measurement?"  The answer to this questions always comes down to duct configuration or duct arrangement.  If you have a duct that is long and straight, then it is a good bet that there are enough "straight duct runs" to get a decent flow profile in the duct and therefore a good flow measurement.  What most customers find is that these long and straight duct runs just don't exist.  In fact, most customers find that there are more turns, twists, bends, tees, and transitions than the even knew they had.

Gas Flow Application Guide

So, how do you know if your flow is turbulent and does not have a good flow profile (i.e. has swirl, reverse flow, cyclonic flow, or flow that is all to one side of the duct)?  For most customers, one way is to go by some guidelines that have been established that give you the best chance of having a good flow profile.  Unfortunately you cannot see the Air Flow through the duct, so you cannot "see" if there is turbulence.  The guidelines provide the number of straight duct runs needed before and after most duct sections or obstructions.  For most typical duct components, this would be 5-8 diameters.  Which, when the duct diameter is large, can be a very large number.

So what do you do when you find you do not have the long straight runs based on your duct configuration or duct arrangement and the guidelines?  That is where the flow straightener and flow conditioner come into play.  The flow straightener helps to get rid of cyclonic flow, straightening out the flow pattern.  Unfortunately flow straighteners only straighten the flow and do not fix the profile, so if the flow is all on the top of the duct, it will not get the flow to fill the duct.

The flow conditioner on the other hand will help to get the flow to fill the duct, but it will not straighten the flow, so if it is cyclonic, it remains cyclonic.  The flow conditioner, like a venturi, throttles the flow through a section that squeezes the flow down that is typically smaller than the main duct.  This allows the flow to fill the smaller section.  Flow profilers also require a huge section of duct in order to take advantage of their profiling capabilities.

The answer would be to use a flow straightener AND flow conditioner.  Something that needs little to no upstream and downstream straight runs and eliminates swirl, cyclonic flow, reverse flow, and profiles the flow to provide a pattern that allows for an accurate Air Flow Measurement. Once such device is the High Beta from Eastern Instruments.  It can be fit to any duct configuration or duct arrangement and in most cases needs less than half a diameter straight run.  Click the link below for more information or email us for more information. http://easterninstruments.com/products/HBP.html http://easterninstruments.com/products/highbeta.html