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Slurry Density Measurement
Are there reliable alternatives available to measuring slurry density except for the Gamma radiation method?
By Peter Green on 30 January, 2007 - 11:59 pm

I would like to know if there are any as reliable instruments available as the Gamma meaurement instruments to determine slurry density. The slurry consists of fly ash (fine ash) and coarse ash from coal boilers and water. Average density varies from 1000 to 1500 kg/m3. I would like to do away with the radiation source to have a nuclear free instrument - if it is available at the same accuracy.

Sure. You can use a coriolis meter.

The problem with this is that the coriolis meter will last about three weeks in a corrosive and abrasive slurry like fly ash.

You could try an ultrasonic density meter, but you won't get the accuracy or the repeatability, and the sensors (if you are correctly using wetted sensors) will be destroyed by the slurry within two or three months.

There are reasons for using nuclear gauges. You just found an application where you can either use a nuclear gauge or keep replacing meters until you learn.

So, unless you want to explain to your management why you screwed up a perfectly good application that might run for another decade without much maintenance in favor of any of several maintenance-heavy solutions, just so you could be 'nuclear free,' I'd stay with the gamma gauges.

Walt Boyes
Editor in Chief
Control magazine
blog:Sound OFF!!

Putman Media Inc.
555 W. Pierce Rd. Suite 301
Itasca, IL 60143
630-467-1301 x368

By Duncan MacDonald on 16 April, 2007 - 10:39 pm

Where can I get a nuclear density gauge? I am struggling to find a US supplier. Is there a trade off in accuracy vs. the need for on site radiation trained personnel?

Ohmart/Vega is a good supplier of these devices. Thermo... now Fisher Scientific had TN Technologies devices. They all can provide excellent product. Ronan also is a good supplier.

Radiation training for on-site personnel would be worthwhile. Don't recall any relation to device accuracy.


By Walt Boyes on 18 April, 2007 - 1:00 am

Thermo Fisher Scientific is the manufacturer of what used to be Texas Nuclear and Kay-Ray. OhmartVega makes nuclear density gauges in the US.
Berthold sells nuclear gauges in the US.

There's three.

It is difficult to talk about accuracy with nuclear gauges, because we'd all rather talk about precision. Nuclear gauges are statistically based devices, since gamma energy is statistical as electrons, not continuous. Precision is "compared to the last measurement" while accuracy is "compared to some standard."

Can a nuclear density gauge be very accurate? Absolutely. You can be very accurate indeed.

There is no tradeoff.

Walt Boyes
Editor in Chief
Control magazine
blog:Sound OFF!!

Putman Media Inc.
555 W. Pierce Rd. Suite 301
Itasca, IL 60143
630-467-1301 x368

By Jon Buchanan on 12 May, 2007 - 5:18 pm

I work for Berthold Technologies USA, LLC in Oak Ridge, TN. We provide nuclear density systems for slurry measurements on a regular basis - flyash slurries, limestone, gypsum, bauxite, etc. In many cases, we can provide an accurate solution with our low-activity sources that don't require shutter checks or leak tests, and that can be installed/serviced by plant technicians without special training. You can contact me at 865-483-1488 if you'd like more information. Our website is

go to
The model is FMG60. Hope this helps.

Unfortunately, Endress+Hauser does not distribute the FMG60 in the United States... at least not at this writing.

There are several suppliers of nuclear slurry density gauges that are available in the United States. The best of them, in my opinion, is Thermo (the old Texas Nuclear AND Kay-Ray brands), followed quickly by Ohmart-Vega (whose nuclear level gauges are better than Thermo's) and Berthold Systems.

There is no trade-off in accuracy. It is all a matter of radiation statistics. The bigger the source, the more precision of measurement.

The problem in slurry density measurement is if you want to measure in "percent solids."

Whether you use a nuclear density gauge, or a coriolis meter, or an ultrasonic or other type of density measuring device, they all measure what we call "bulk density." Actually, they all _infer_ "Bulk density," and that can be a problem in itself.

In order to accurately calculate "percent solids" from bulk density, it requires to know the dry solids density, and the fluid density.

Generally, the fluid density is approximately equal to 1.0 g/cc or 1 SGU, because most slurries are water based. If the slurry isn't water based, again it is a different story.

Where the problem exists is if the dry solids density changes. When you have a variable constant, the Finagle Constant intervenes and makes your mathematics mush.

Other problems for density calculation happen when the measurement is of sludge density in wastewater treatment. Typically, the dry solids density of activated sludge is about 1.6 g/cc. Since the apparent density of water (when measured by a nuclear density gauge, anyway) approaches 1.1 g/cc, you can see that trying to read 5% solids with any real hope of either precision or accuracy is a forlorn hope.

You do not, necessarily, have to have licensed and trained staff on site, but it sure helps, and is way cheaper in the long run.

Walt Boyes
Editor in Chief
Control magazine
blog:Sound OFF!! _________________

Putman Media Inc.
555 W. Pierce Rd.
Suite 301
Itasca, IL 60143
630-467-1301 x368

By D Willard on 3 June, 2009 - 11:08 am

Bully, Walt,

I agree completely. I foresee two problems with this advice.

Government regulations (AEC) require that there is a trained person available for handling these nuclear elements; things are much worse now that people have realized that these elements, made of spent rod material, make good dirty bombs. You can hire help but they must be available 24/7 if you need to work on the LT/LE.

The second problem, though not nearly as bad, is that your slurry may coat the sides of the vessel. I am not sure how this will affect density measurement but it could reduce the LE transmission strength. I know we saw a typical life of 8-10 years with these elements, maybe more; the signal grows weaker. It seems to me that the thicker the wall, or the build-up in the tank, the shorter the useful life.

Another minor issue is the construction. These elements weigh more than gold. I built one that required 6-inch I beams.


Sorry, Walt, misread your post.

Slurries are not the automatic killers of density meters, however.

The tube type density meters were the standard solution for china clay slurries until replaced by the tuning forks. The reason or replacing them was not erosion but installation cost and maintenance issues. They had to be installed in a bypass and protected against freezing with trace heating.

Tuning fork installs directly in to the pipe.
Of course, china clays are not particularly abrasive.

Chalk slurries are as they contain bits of lint, impurities in the chalk and even bits of excavation equipment.

One unit I witnessed had been in service for years in a side of pipe installation and showed serious erosion on one side. The reason it was replaced was because it had taken a hit from something heavy enough and moving fast enough to bend one tine right over and bend the stem. Since these were 316 stainless bar stock, this took some doing.

It would not today be installed as it was then. The long stem options allows the sensor to be installed much more flexibly.

Because they can be installed in any size pipe, it offers the opportunity to pick a cross-section with lower flow velocity.
All that is needed is to periodically check for calibration drift due to erosion and apply a K0 density offset.

Ultrasonic sensors are available for this application which are very easy to install & handle unlike nuclear ones.

Go to for further details.


While sonic density may seem to be an alternative to nuclear density, I would caution that the sonic systems are not suitable for heavier solids slurries. Non-linearity of measurement and lack of precision are negatives for this type of measurement.


I would have a look at Micro Motion Coriolis for this measurement. An earlier post identifies a potential issue with corrosion. While I do not agree with the "3 week" sensor life statement, I do agree that corrosion/errosion is a concern... but there are ways around the issue. Since density is the req'd measured variable, one option may be to oversize the meter to keep the velocity down or mount in a slip stream configuration and limit the velocity thru the meter. Contact your local Micro Motion representative... they MAY be able to assist you... it would be worth a shot anyways.


Dear Anonymous,

I have spent over a decade making this measurement. Anyone who would suggest a coriolis meter for this measurement is doing his client or customer a grave disservice. I don't care whose coriolis meter you suggest.

I don't care whether you agree with "3 week" sensor life or not. I have _seen_ this life expectancy personally in this application.

There are some things coriolis meters simply cannot do. Abrasive slurries are a significant part of that.

What part of "really bad application" didn't you get?

Spending upwards of $5000 US on "worth a shot" is bad advice.

By Anonymous on 3 March, 2007 - 12:31 am

Wow, I did NOT recommend running out and spending $5K... I simply stated that it MAY be worth while looking into... as in at least making a freakin' phone call!! So if you call that "bad advice" then that is your choice I guess. BTW, I don't see "really bad application" anywhere...

I see lots of horrible, questionable advice/suggestions on here. Do you always jump in and "Slam" the folks here?

I didn't realize your reply was the "Be all" answer. Isn't that the purpose of this board... to solicit advice??

Have a great day!!

By Walt Boyes on 3 March, 2007 - 5:16 pm

No, I don't jump in and slam the folks here. YOU posted as "anonymous" and provided some very bad advice. That advice might, if the original asker took it, and put the coriolis meter in, have cost him his job. If you had read upthread you would have seen that people had already talked about the highly abrasive conditions in a fly ash slurry.

BTW, I had the occasion to discuss this application and your answer with one of the top experts of one of the largest coriolis meter manufacturers a couple of days ago. After he quit laughing, he said that his company wouldn't consider selling a coriolis meter for fly ash slurry, and he doubted any of his competitors would, either. The subject wasn't even worth
your "freakin' phone call."

He recommended, as did I, a nuclear gauge.

If you want to be taken seriously post with your name and affiliation.

Walt Boyes

By Anonymous on 4 March, 2007 - 2:06 pm

Look at the website from Krohne

l. They have got a mass flow meter for abrasive sludge/slurries (Type Optimass 7000). The major advantage of Krohne mass flow meters is that they use a single straight measuring tube. Give them a freakin' phone call and find out what they think.

I'm sorry for the anonymous respond, but if you got comments post them thru this website so others can learn from the discussion.

By Walt Boyes on 4 March, 2007 - 4:12 pm

Ok, Krohne is the ONLY coriolis meter manufacturer that sells something they
say will work in abrasive slurries. I suppose you work for them. I am not
going to argue that they should not. Krohne is a reputable company. In fact,
I was the first Krohne America representative in the United States.

But I still think that the correct technology is nuclear.

Walt Boyes
Editor in Chief
Control magazine
blog:Sound OFF!!

Putman Media Inc.
555 W. Pierce Rd. Suite 301
Itasca, IL 60143
630-467-1301 x368

In the mining industry, slurry density is commonly measured by using dual bubbler tubes and pressure transmitters. Very cheap, stable and accurate.

By Abhijit Goswami, Haldia on 2 March, 2007 - 11:54 pm

I agree with Walt. In fact, if law of land permits, better to go for nucleonic sensor, which, if carefully selected, will be reliable for years.
As the pipeline diameter/thickness is not known, identifying source strength is difficult, but with a scintillation counter type detector, you may get benefit of selecting lowest source strength.

What needs to be deliberated at your end is:
1. Orientation of sensor in pipeline so that the radiation towards detector is preferably away from common manways, if at all acceptable.

2. Administrative control through:
a. Awareness/training
b. Safety marks
c. pocket dosimeters for operators/technicians working around

3. Periodic inspection of source leakages:
a. Through surveymeters
b. At frequency as guided by statutory bodies
c. Reported by (own) Radiation Safety Officer to statutory bodies

4. Decommissioning:
a. Be careful to choose a source with appreciable halflife.
b. Disposal guidelines

Selection of a fireproof source is a good engineering practice.

I am not aware of bubbler measurement in similar service but technically it appears to be quite feasible except for calibration reference because it may be quite difficult to predict slurry distribution (density) on a horizontal pipeline which may be dependent on flow and other conditions too.

By Michael F. Palmosina II on 21 March, 2007 - 10:53 pm

I have been recommending the nuclear solution for density measurement of continuous process of slurries for many years. If anyone has a better solution, please advise. I was given the information on "vibrating tubes" and "coriolis tubes", yet was also instructed these methods were not recommended for longevity in slurries.

The material in the slurry is a polyol blend and wollastonite. There are other, less abrasive materials carried as slurries in polyol blends but the most common is wollastonite.

So, if there is a better idea than nuclear, I am open to it! Thank you.

Michael F. Palmosina II
Senior Technical Service Specialist
Bayer Material Science, Llc.

By Alex Kulik on 9 May, 2007 - 1:00 am

How about a compact (20 cm) high energy X-ray machine? Offers nuclear performance but you can turn it off whenever you want to.

By Nathan Boeger on 25 September, 2007 - 10:54 pm

This thread makes me laugh! OP suggests removing radiation sources to be nuclear free as long as accuracy isn't lost, suggesting that price is of little object. I'm wondering if I should market $5,000 smoke detectors.

Then Walt responds with a pretentious show of good advice and gets into an arguement with anonymous. He then laughs at anonymous' idea with a top industry expert over a cup of tea and truffles.

Hard to take sides here. If you haven't seen this whole thread, I'd recommend it! Good readin's. You'll know who to direct your next question about nuc gauges to.

Nathan Boeger
on behalf of myself

I'm glad you enjoyed the free advice.

I would ask you to tell me why my "show of good advice" was pretentious.

Been there, done that, and the tee-shirt got so raggedy I tossed it.


This thread is amusing indeed, and if Walt doesn't think he was pretentious just for someone providing alternative advice to his own then he is disillusioned. Is this site not for helping people and giving advice, not to shoot down anyone who doesn't share your opinion?

I think people need to remember this, and that if 100 engineers were given the same problem to solve you'd get 100 different solutions!

More to the point though, I agree with Walt's advice that a gamma source density meter would be the best option, although I am not familiar with the specific coriolis meters mentioned above and so cannot comment. Probably worth investigation though, as it would more than likely be significantly cheaper.

By Nathan Boeger on 28 September, 2007 - 12:52 am

I like you Walt. You're knowledgeable and you know it - and too well written for me to get into a debate with. Lucky for me, I don't know a thing about Slurry Density measurement.

About you coming off as pretentious -

>You just found an application where you can >either use a nuclear gauge or keep replacing >meters until you learn.
>So, unless you want to explain to your management >why you screwed up a perfectly good application >that might run for another decade without much >maintenance in favor of any of several >maintenance-heavy solutions, just so you could be >'nuclear free,' I'd stay with the gamma gauges. <

Or was it this one?

>Dear Anonymous,
>I have spent over a decade making this >measurement. Anyone who would suggest a coriolis >meter for this measurement is doing his client or >customer a grave disservice. I don't care whose >coriolis meter you suggest.
>I don't care whether you agree with "3 week" >sensor life or not. I have _seen_ this life >expectancy personally in this application.
>There are some things coriolis meters simply >cannot do. Abrasive slurries are a significant >part of that.
>What part of "really bad application" didn't you >get?
>Spending upwards of $5000 US on "worth a shot" is >bad advice. <

No, the best one, my personal favorite, was about laughing over anonymous' coriolis meter recommendation with the top expert and how you cleverly ended with it not being worth the "friggin' phone call".

The thread really made my day. Who ever thought that you could learn so much about a technically obscure (well, very specific) topic and get such a good laugh? The really great part was that I constantly shifted who I sympathized with. I don't think I'll every forget that coriolis meters aren't the tool for measuring the density of abrasive substances. At the very least, I'll know where to go when it comes up.

I do feel your pain, though - about forum posters constantly bringing back a technically incorrect/irresponsible application. Can you mow your lawn with tweezers? Maybe. But why? On the other forum guys keep coming back asking how to make a custom data historian using DDE calls in a VBA script from within Excel. I don't mind the first timers who know that Excel can read OPC data, and naturally try to expand it. It's the know it alls who pipe in with poor advice that get me going! They take my advice "that it's clunky and hard to do" as a challenge, disregard "lots of cheap applications already accomplish what you're looking for" and completely ignore numerous strong points about why data logging should occur in a database, not a spreadsheet. Even stubborn HMI vendors figured this one out in the 90s. Somehow the question keeps coming up and "programmers" keep recommending it. Ughh! Dishing out that much pain, frustration, and opportunity cost should be illegal! Enough on that

Nathan Boeger
"Design Simplicity Cures Engineered Complexity"

By Guest Author on 24 January, 2008 - 12:39 am

As one who has significant experience in using nuclear devices to measure slurry densities I can offer the following:

If the device can be calibrated with repeatable and representative sampling, there are no better ways to obtain this measurement. These devices have been in use for many many years and with proper education and handling they are as safe to use as anything else. Two things may add errors to the reading. The first is Compton scatter. As the gamma photons pass between the source and the detector some are scattered out of the direct line of sight to the detector and then are re-directed back to the detector. They do so at a reduced energy. However the detectors cannot discriminate between energies and therefore if this scatter is not exactly the same for all densities there will be a small error for any measured densities that have not been verified by sampling.

The second point is that these instruments respond to three things. The distance between the detector and source (which is constant) the density of the material between the source and the detector, and finally the composite absorption co-effieient of the material. For most elements having a mass number (Z) of about 50 or less this remains constant. This includes iron, carbon and many other elements your meter will be exposed to. The major exception is hydrogen. Hydrogen has twice the absorption rate as do the other elements for Cs137 for example. As the density of your fly ash changes so does the hydrogen content, and so also does the composite absorption co-efficient. The meter however only is set up to respond to density changes and so it will be in error as the ratio of hydrogen to solids changes.

These errors are small, depending on your range, source size and geometry of the installation, but overall there is nothing that can even come close to the reliability and simplicity of these devices.

Use them with confidence!!!!


I worked in the mining industry for many years. My favourite Nuclear Density is from Ronan,
see Toronto based I think. I haven't used one for a couple of years but I see they claim that the source is now so weak in some cases you don't need a license. A far cry from the 2 Curie source I used 20 years ago (level application). I agree they are very reliable.


By Dooley, Vince on 26 January, 2008 - 3:01 am

I don't remember whether it was this list or another where someone suggested using a coriolis meter on a trolley as a reference meter to calibrate nuclear density gauges. It is connected to the sample point. The fluid is run through the reference meter to drain during the calibration check. It is then flushed with water and the reference meters calibration checked on the water. It certainly overcomes all the issues with sampling.

Some nuclear density gauges are not affected by forward scatter. An electronic energy discrimination window is set up around the energy of interest to eliminate forward scatter and background. In some cases two windows are set up. One covers a band just below and up to the peak of interest the other just above. Automatic gain control can then be achieved by adjusting the voltage so the count in each window is equal.

Vince Dooley

Well, a visit to the Micromotion site will show you the range of density meters they offer. These are what used to be the Solartron sensors and you will see they have fork type density sensors.
These use the vibrating element principle where the resonant frequency is a function of the density. The fork types give accuracies of around +/-1.0kg/m3. Obviously significantly lower than the tube density meters but popular in a range of applications because they can be installed into the main pipe line, especially now they are available long stem (up to 4 meters long).

The key to erosion is velocity and shielding.
Coriolis meters employ relatively thin walled tubes and often have a complex flow path that leads to erosion spots just after the bends.
With a fork sensor you can use the long stem version and install on an elbow in the pipe or through the side wall at an angle such that the tines the sensitive part of the sensor, are directed upstream or downstream.

The sensor itself is a tuning fork spark eroded from bar stock and the spigot is machined from bar stock. The long stem version is basically a length of 40mm sched 40 pipe with the sensor mounted on the end.

These sensors have a history of use in slurry applications ranging from china clays (not very abrasive at all, originally used the tube type density meters but then moved to the fork type) through to granite washings plant underflow and, as a viscometer, chalk slurry.

The chalk slurry application is worth considering.
Chalk is quarried for the cement industry and in those that use the wet process the chalk is made up into slurry to be pumped to the cement works. The higher the solids content the less energy required during subsequent processing. Solids content is a function of pumpability which is dependent on the viscosity. A viscometer (the self same tuning fork used for density)is used to measure the viscosity and determine the amount of viscosity modifier to be added (ligno-sulphontae, I seem to recall). This reduces the viscosity allowing a higher solids content. % mass solids is a standard inbuilt calculation with these sensors.

The chalk slurry is abrasive. It contains whatever other material is in the chalk, e.g. flints and occasionally small bits of mining machinery. Go to this page and see a short stem fork that was used on this application:

This is a sensor that was in operation for around five years. The installation was not ideal and the sensor suffered continuous abrasion as can be seen and finally, was evidently struck by a large lump of something moving pretty fast which bent the tine over. The sensor was still functioning when received back at the factory.

Over the years they compensated for the erosion by periodically re-calibrating the sensor (a simple density offset value). With the modern long stem sensor and modern installation methods this type of erosion ca be managed much better.

Yes, Walt is right, any time you put anything into a flowing stream of abrasive slurry you will get erosion if you expose the sensor to high velocities but by angling the sensor downstream the sensor will prove very rugged and durable. It now depends on what life time you can live with, it will be substantially more than three weeks. We are talking many years. The sensor shown in the link was five years in a bad installation (they did not have the long stem version then) so in that same application a long stem could be expected to survive significantly longer than five years.

But if you want to move away from nuclear devices, you can get very long service life with a well designed installation i.e. by carefully choosing where to install and how to install.

Re: Abrasive Slurry

I worked in the mining industry for many years, for abrasive slurry they typically use rubber lined pipes keeping the velocity quite low. I wonder if any coriolis manufacturer has tried the rubber lining approach. A rubber product I have seen 'LINATEX" is very soft and will outlast the hardest metal in severe abrasive applications.
I have also seen differential pressure used to measure density where the slurry is traveling in a vertical line, 2 taps about 3 ft apart flushed with water.

I must agree with Walt however that Nuclear Density is the most reliable method. In my experience it has never been much of an issue getting approval. The manufacturer will be most helpful in this respect. Check out "Ronan" my favorite by far.

In mining the meters typically output %Solids by weight, not density.

Something to be aware of in horizontal service is stratification, you will get a different reading depending on if the beam is vertical or horizontal. It is also difficult to get a representative sample of a slurry for the same reason.

The "Solatron" fork type density sensors sound interesting, perhaps they would also benefit from rubber coating.

"An interesting article I read recently claimed that rubber is non compressible - think about that one".



By Danny OConnor on 29 March, 2008 - 12:03 am

There is always more than one way to skin a cat! Coriolis can and will work and is the easiest way to do it. You simply need to oversize the meter slightly and pick a suitbale material for it. The manufacturer I work for (E+H) has a range of straight tube meters and we have also supplied 10" models on mud flows from oil wells. The second option is to go for a vibrating level switch optimised for density. These simply sit in a line with a temp probe and go back to a controller. The varying density has a noteable effect on the 'tuned' switch and as such this change in vibrating frequency is detected by the controller - using the temp probe to offset any effects of temp on the product.

An interesting read.

I've had a pilot plant in operation where (for reasons of portability) we avoided installing a nuclear gauge for the measurement of lime slurry densities. Instead installed an E+G coriolis flow meter and a tuning fork. The tuning fork was very unstable but we didn't spend too much time trying to work it out because the coriolis (straight through type) worked reasonably well.

The coriolis meter was installed on a recirculating loop to provide a controlled flow rate through the instrument. We operated the plant for approximatley 100hrs a week for about 9 months with the same flow meter.

It was good enough for our purposes (control of lime dose rate to the process)- although occasionally it would appear to be "out" when copmared to our operational samples (but then again sampling slurries isn't easy--and the analysis was by weight and volume--not by filtering and drying the solids).

By Angel Munger on 25 November, 2008 - 1:34 am


I don't know more about pumps but I know who can help you. You should contact with the members of the Toyo Pumps at this URL Because Toyo Pumps North America is proud to be the only authorized distributor of Feluwa High Pressure pumps and parts in the Americas; their pumps handle everything from dirty water to the heaviest slurries. Toyo Pumps has different types of pumps and pump sets like horizontal pumps, submersible parts, agitator pumps, submersible pumps, slurry pumping, recessed impeller pumps, industrial pumps, vortex pumps, mining pumps etc.

I hope they will solve your problem.

Thank you,


By Craig Hannah on 11 May, 2009 - 8:51 pm

I just performed flow loop testing on what I believe is the same material -- FGD -- a power plant by-product--made up of fly ash.

I believe you are looking in the 1.0 to 1.5% Total Solids range. The unit measured based on microwave technology so you would not need any special license, training. Let me know if you are interested. My cell 678-772-9584 or email

Craig, I am interested in this. Give me more details.

suvit.lee [at]

By Roy Matson on 11 August, 2009 - 7:41 pm

1.00 - 1.50 is easily achievable with a differential pressure transmitter using diaphragm seals, bubble tubes or water purge.


By Enrique Rengel on 4 June, 2010 - 5:06 pm

We have developed an densimeter for slurry for mining and other applications that not use radiation. The principle of measurement is on line weighing of sample with constant volume. Complete specifications for your application we can offer.

By Walt Boyes on 5 June, 2010 - 2:11 am

Send me some information off the list, please.

Walt Boyes
Editor in Chief
Control and
555 W. Pierce Rd Suite 301
Itasca, IL 60143

wboyes [at]

By Robert Batey on 24 January, 2012 - 5:44 pm

>Send me some information off the list,
>Walt Boyes
>Editor in Chief
>Control and
>555 W. Pierce Rd Suite 301
>Itasca, IL 60143
>wboyes [at]

I was intrigued to see the historic interest on the topic of continuous measurement of abrasive slurries in heavy industrial environments.

There now exists a continuous mass per unit volume measurement (yes mass, not weight), suitable for mining, dredging, fly ash and similar slurries. Please go to to put all minds at ease. This is suitable directly for wet density or, knowing the carrier sg and solids sg, % dry solids is continuously computed.
The density meter may be used in series with a high quality magnetic flow meter for measurement of wet or dry mass flow. The problems in your thread of articles are finally and reliably solved.

Robert H. Batey

Is there any link with the earlier post by Enrique Rengel?

He talks about an inline weighing device.
Gravitrol style perhaps?

I would love to hear more about the non-nuclear density measurement options. My application is the coal industry. We have large particles (-50mm), at slurry densities around 1.6 SG.

Please email at james.agenbag [at]


I find you while searching for any sources for slurry density measurement. I have a 2m pipe in which fine clay particles settle. how can i measure solid % in diff levels at the same time.


If what you want is simple bulk density, taking into account stratification, there are a number of (expensive) ways to do it. One is with a gamma nuclear device that would consist of an insertion source at the top of the pipe, and a bar-type scintillation detector at the bottom of the pipe. If you want to pursue this, see a nuclear gauge vendor like OhmartVega or Endress+Hauser or Berthold.

If what you want is to know the density of each stratification, I think you are SOL.

The other problem is what the ratio of the fine clay to the carrier (which I assume to be water) is. If the dry solids density of the clay is, say, 3 or 4 g/cc, and the concentration isn't in mg/l, you may be able to do the radiation-based density measurement. If the dry solids density of the clay is 1.5 g/cc, you are SOL here too.

Why do you have a 2m pipe? Can it be necked down to go through a coriolis meter? They make them up to 12" now, and I understand that somebody has a 16" on development.

Hope this helps. If it doesn't, send more data please.

Walt Boyes, Fellow, the International Society of Automation (ISA)
Editor in Chief
Control and
555 W. Pierce Rd Suite 301
Itasca, IL 60143
wboyes [at]

All due respect to Walt but the answer to any density problem isn't always coriolis meters.

Slurries are not necessarily a problem for tube type density measurement, many hundreds have been used for china clay slurries, for example, but for abrasive slurries then there can be a problem for tube types, especially twin bent tube coriolis.
The two principle problems would appear to be erosion on the bends and tube plugging where one or other tube might block.

One usually finds that the tube wall thickness leaves something to be desired if erosion is expected.

So at the very least you would need to look at straight single tube designs.

But a good option is the tuning fork sensor.
This is very rugged, the sensor being spark eroded from bar stock and the support structure also being bar stock, and they can take a lot of punishment.

I have seen one returned from a chalk slurry application where it had obviously finally met its end after being hit by something very heavy moving very fast in the pipe line but wit evidence of long term erosion that had been compensated for by periodically applying a simple density offset to the calibration.

The option to look at is the 7828, possibly thee long stem version:

The key is to choose the right version for the application and install to suit the process conditions.

I am sure the medium of slurry of fly ash is high-ware medium. What kinds of valve that you are using?If you are looking for a ware-resistant valve please use our ceramic-lined ball valve which is excellent for ware-resistant and corrosion-resistant.With very long service-life.

Please visit us at contact us by

Best regards

Sales manager

There has to be a better way to organize thee threads. I just noticed the original post was in 2007. I could have saved my energy as the OP has obviously long ago made his decisions.

Interesting new discovery about coriolis.
Slurries are not Newtonian so this article from TUV NEL should be interesting to advocates of coriolis meters.

I have to ask again. Why hasn't some corolis vendor come up with a rubber lined version for abrasive slurry.

Seems to be a no brainer.

Ronan Nuclear is still my favorite


What about TOSHIBA microwave density meter? do they work?

By T. McCarthy on 30 June, 2011 - 3:17 pm

>What about TOSHIBA microwave density
>meter? do they work?

ANALYTICAL FLOW TECHNOLOGIES makes the DENSITRAK LIQUID DENSITY METER (originally with Calibron and Honeywell). The DENSITRAK is used in the Petroleum Pipeline and Refinery,chemical processing, semi-conductor production, pharmaceutical, blending and slurry industries. The Densitrak utilizes the oscillating U-tube to establish the density of liquids and gases based on an electronic measurement of the frequency of oscillation, from which the densiy value is calculated. A change in the vibrating mass(as a result of the fluid density) shifts the resonant frequency. A New state-of-the-art Density Processor with a Proprietary Windows Based Software Package for graphically monitoring real time density, pressure, and temperature is utilized with the Densitrak. The Densitrak comes in different models and the engineers review each application to determine the model that best suits the specific application.

You don't show how the Densitrak can better any of the sensors discussed above when its design seems to fly in the face of the various concerns expressed in earlier posts.

One of the reasons for the upset about coriolis meters with abrasive slurries is because the tube(s) are pressure containing and they are thin walled in order to flex sufficiently.

They are also bent into complex shapes.

This is probably the single biggest source of concern.
Note in the discussions above that success comes with straight tube sensors. And more than that, with reasonable bore sizes. Hence the Khrone straight tube and, if I was to choose another, possibly the E&H Promass. Also the Solartron 7845 but at 1" it ends up in bypass flows. Still, 1" is a reasonable size for a bypass sensor.

Of course, for density you don't need the flow velocities you need for mass flow so you can size the meter for the optimum flow velocity.

Bends are vulnerable to erosion.

Also, at any reasonable flow the bends will tend to centrifuge the slurries intensifying the erosive effects, usually causing the most erosion not on the bend itself but at a point on the exit.

If the flows are lower then you have the possibility of drop out.

Personally, I would be very concerned that small bore tubes will be more prone to blocking than larger bore.

By Walt Boyes on 5 July, 2011 - 12:47 pm

If you want to solve all the wetted-parts issues with slurry density measurement, contact Berthold Systems or OhmartVega or Endress+Hauser for a very low power source gamma densitometer. Don't re-invent the wheel.

Walt Boyes
Editor in Chief
Control and
555 W. Pierce Rd Suite 301
Itasca, IL 60143

In terms of the original post way back when, the objective was to seek an alternative to radiation technology capable of equivalent accuracy.

This is not unusual. There is nothing wrong with this. And if the choice is to choose a vibrating element sensor or some form of ultrasonic device, whatever the pro's and cons technically, it will be the right choice in view of other factors.

Sure, there will be trade-offs. It depends on if the downsides of alternative technologies are more manageable than the downsides to radiation technologies.

If we move away from nuclear devices then we may have to trade away some of the benefits for others we value more.

To trade off unlimited life span for no a special skills or precautions sensor is, to some, an acceptable outcome.
It may be purely commercial concerns that take precedence.
It may be that the technology is not as good as we would like.

I showed the example of a tuning fork used in a chalk slurry pumped from the quarry to the cement kilns. Five years service before an exceptional event did serious damage. Something that is far less likely with the technology today.

Much of this discussion has focused on vibrating element sensors.
Tube or insertion?

Conventional twin bent tube Coriolis we can agree are not a good choice.

I'd be very concerned about small bore by pass sensors.
If there were no other choice I'd want to use the straight tube density meter in a bypass but for preference the tuning fork in the main line or a full bore straight (or nearly so) single tube mass meter. Maybe they won't last as long as radiation devices?

But there is more to choosing a technology than the optimum measurement or optimum life expectancy. Some features can be sacrificed for others.

Some of us might think a wrong choice is if the sensor fails in a short time or is grossly inaccurate.

Others may decide one sensor is better than another because of its cost of ownership rather than its cost of sale. (though more usually purchasing will decide capital cost is more important that operating costs).

In the modern world, we often do not get to make these choices.
It is a rare luxury for a process engineer to search the literature, call in reps for different technologies and make his choice based on the best technology for the job.

De-manning means there are fewer engineers to do all that needs to be done, and no time or money for the engineer to spend on such searches.

And purchasing do not find it cost effective or good use of their buying power to maintain a hundred suppliers for a couple of hundred different purchases.

The result is what we have today.
The rise of the "Single source supplier" and "strategic alliances".

Today the process engineer will simply fill in a form for a sensor stating his process conditions and what he wants to do. Purchasing will buy whatever the single source supplier has available as a "best fit" and it is the supplier that will dictate what that is. It is increasingly difficult for the engineer to buck the system and reject thee single source purchase.

The article "Flowmeter selection: Right size, right design" at suggests that of all installed flow meters, 70% are the wrong size or the wrong technology.

I would suggest that ought to read " ...are sub-optimal size and technology choices."

Whether a flowmeter or any other sensor, the ideal might be for 2.5" pipe size and our first compromise is to choose 2" or 3".
So we sacrifice "ideal" and settle for "Optimum".
Now that we live in an age of "single source suppliers" and "strategic alliances", the purchase will not necessarily be the optimum sensor choice. It will be the best fit from that suppliers product range, a sensor that "does the job".

It doesn't mean you will get the "right" size or even the "right" technology.

For single source suppliers, the ideal is a single product that serves all applications. It does not have to be ideal in all nor the optimum choice in all.
If most applications could be met with one of four or five different technologies it makes sense to focus on the technology that covers the widest range of applications. Why manufacture all five technologies when one will do?

This is one reason why coriolis is so popular.
It is the nearest to a universal technology we have.
In an application where Magflow is the optimum choice, the buying process may result in coriolis.
It does the job but maybe it costs more to buy and has a higher headloss and a bigger footprint, but magmeters are limited to conductive fluids.
Coriolis are not.
Turbines are limited to low viscosity fluids. Coriolis are not.

Today you may find you can still get the magmeter. In the next few years? When R&D focus is to make the coriolis all sing and all dancing and little or no money is invested in other technologies?

For those of us who like to get things "right" this is not a good move. But what makes the Mag meter "optimum"? In the end, when all things are considered, it is the coriolis that is the optimum choice. At least, it is when this is just one application among many.

It means that the compromises imposed by the modern purchasing model and limited resources and skills client side, the use of "product selection programs" supplier side (can you find enough staff expert in all the products?

No. You have selection programs and you support with industry and product specialists who may get involved if enough is at stake) and the limited choices now being offered by "single source" suppliers" result in sensors being supplied that will often be not the first choice of technology, that may not be the best of that technology and may also be the most expensive of that technology.

But they will "do the job".

We perfectionists may place a lot of value on being able to search out and select the best technology, find the best manufacturer or the best price but there are factors outside our control today that mean we will not get out choice.

We will get what we are given.

So it may be that nuclear is the best possible technical choice and there may be one manufacturer that is seen as the nest manufacture of that technology.

It doesn't mean that you will be allowed that choice. Other selection factors will take priority.

For most applications near enough is probably good enough.
The problem will come when the "single source" model results in some dangerous choices too often repeated.

It is a familiar situation where manufacturers market their products claiming success from applications where they are far from the best choices. And if this sort of activity comes to inform the product selector programs.... ?
When does the model start to fail?

I found your comments to be very useful and general enough to be applied to any technology. Lots of good advice for when we have to make those difficult choices.


By paul skingley on 27 July, 2011 - 4:26 pm

we have refreshing news for you gentlemen sciam engineering inc manufactures a non nuclear density meter which directly and continuously measures weight per unit volume of dredging and mining and similar slurries this is explained on

A German company and the USACE developed a "High Resolution Non Nuclear Density Profiler For Dredging Residuals and Fluid Mud". I think the company is Innovision.

My German colleagues told me that they are offering the technology for process control, too.

Is the density measurement through a pipe or in a holding tank before being fed.

Through a pipe, I have used the Krohne single tube coriolis. If your process solution coats though like mine did, you will have heck of a time to clean it out and do density calibration on the unit.

I ended up going low tech and using dual bubbler system to measure density.

Using two Ti pipes in our holding tank at known heights. Able to back calculate out density with pressure measurements.

> I ended up going low tech and using dual bubbler system to measure density.

> Using two Ti pipes in our holding tank at known heights. Able to back
> calculate out density with pressure measurements.

Many years ago I worked at a mine where we measured the density on the cyclone feed lines (vertical flow up).
Two taps about 3 feet apart purged with fresh water and measured with a DP cell.
I still think Ronan nuclear density is the best solution.



I'm struggling in measuring cement slurry density while cement job which is pumping out to the well by HP cement units. I'd appreciate if you advise/suggest what kind of densometer and flowmeter I can use?


By Marius de Vries on 23 March, 2012 - 12:53 pm

For application in cement, drilling a new technology came into the market. Ultrasonic sonochemisty. Check our
Density is measured by means of ultrasonic sound

Regards Marius

By Paul Jones - BSME, MBA on 19 June, 2012 - 5:01 pm

determine the status of your most current interest in the newest advances in Density Flow Measurement. ( Please log onto our website, if you have not done so lately. We have made a few updates.

I'm here to support you and answer any questions you have regarding our DM3 Non-Nuclear Density Meters.
- better accuracy
- lower lifetime costs
- handles vibrations and tilt
- 2" - 40" diameter pipes
- wide variations in temperatures

Paul Jones - BSME

I didn't read all the way through the blog, but the indications I got is a Coriolis meter would not last. However, my experience with Krohne's Optimass 7000 Series would indicate otherwise. We've had them installed for quite some time on lime slurry and they have performed well from a stability, accuracy, and reliability standpoint. This straight, single tube design made from titanium is worth investigating further.

Here we are in 2019 and I'm reading all these suggestions for non-nuclear densometers:

This thread suggests the Sciam DS3 back in 2012 - they no longer exist. Another thread from 2015 suggests the MPV MassExact - they no longer exist.

I just stumbled upon REDmeters RM_ series.

As best I can tell, it's the same product through several corporate rebrandings. The tech seems simple: measuring the deflection of a rubber pipe. Now, does it actually work?

This thread has been very informative. I have many customers who need non-nuclear.

Straight tube Coriolis makes sense - Krohne should have application references.

I'm also waiting on a response from Red.

Ultrasonic options seem to be weak at moderate/high percentage solids values.

I'll be looking into the pressure measurement approach mentioned many times in this thread. Perhaps a good low cost...decent approach (?)