#solids flow

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

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

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

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.