Slurry Density
Observation vs Awareness

A comparison of non nuclear density measurement methodologies

We have found that observation and awareness are often conflated. Because of this, clearly delineating the two can be confusing. As an illustration, consider when you step onto a scale to weigh the damage that all the holiday feasting and snacking has done. The scale is only observing the bottoms of your feet. However, the scale becomes aware of your mass through the downward gravitational force exerted through your feet.

Similarly, methodologies of non-nuclear slurry density meters can easily be confused as being one in the same. In this article, we compare intra-media measurement, which creates an observation of media, versus Red Meters’ methodology, which creates a complete awareness in real time.  

Observation Points | Intra-Media Measurement

The status quo of density measurement for the past fifty years has been intra-media measurement. To explain, this is when a signal, either gamma rays or sound waves, is blasted through a  small percentage of the slurry from a source. Next, the signal is received on the other end of the pipe for interpretation. As a result, a single observation point is created at the receiver, from which an inference is made about the full slurry.

Although these technologies have numerous limitations, such as  signal infidelity at incompatibility with high solids concentrations, the primary limitation is that they are only aware of the specific slice of media through which their signal passes.

In effect, the reading taken represents a very small part of the larger picture.

slurry density Zone of Awareness | A-to-b and fan signals

Slurry density meters that use gamma rays or sound waves create A-to-B or Fan signals. 

In meters with A-to-B signals, measurement data of the slurry density is restricted to a narrow slice of the pipe’s diameter. Similarly, fan signals are able to provide slightly more awareness of slurry at the moment at which the observation is taken. However, neither of these provide full awareness of the pipe contents.

The diagram below helps demonstrate this visually. 

Another key point to consider is that, in many cases, these signals are not being received continuously. As a result, the measurement of the slurry density is limited to a fraction of the pipe size and an even smaller representation of the density of the slurry over time.

Full Volume Slurry Density Measurement

As you are likely aware, the calculation for density is Density = Mass over Volume. With this in mind, you should be able to see the benefit of a methodology to measure slurry density which relies on reading the full volume of material as it passes through a pipe.

The Red Meter uses this calculation as the basis of it’s principle of operation. However, the technique to measure the full mass of what is inside the Red Meter’s cartridge differs slightly.  To explain in more detail, using a known mass and volume, the density of slurry inside the cartridge can be accurately calculated. The Red Meter Toro uses its mass observation point to gain awareness of the density of the entire cartridge in real-time as the slurry passes through the pipework.

If you imagine a slurry with large chunks of debris or compacted solids randomly dispersed throughout, then the advantage of full pipe awareness becomes clear. Measurements which reflect small a small representation of the slurry only give a small part of the picture and, more importantly, are often leaving out significant pieces of the puzzle.

When using a measurement methodology which gives you a full volume measurement, you are no longer playing a game of hit and miss accuracy. Which is to say, you are not relying on chance to pass a representative slice of slurry through your signal at the exact moment of the reading. 

nuclear density meter losing accuracy
Red Meter Cartridge
nuclear density meter losing accuracy
Zone of Awareness

A-to-B Signal | Fan Signal | Red Meter

slurry density | The Full Picture

For those looking for very rough outlines about their slurry characteristics, the status quo technology will probably suffice. However, when tight process control is required, building your measurements on random chance will always be a game in which the odds are stacked against you. Now that a proven solution for slurry density measurement which provides a full picture of what is happening in your pipeline is available, you don’t need to rely of guess or chance to determine the characteristics of your slurry. Using a measurement tool with the awareness provided by the Red Meter Toro is the best way to defeat the odds of chance and be fully informed.

Guide to replacing nuclear density meters

Although the reasons or timing may vary, most industrial measurement processes will
at some point need to consider replacing their nuclear density meters.

This guide details the options and process of replacing nuclear density meters.

Learn more

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