# Slurry Density Measurement

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#### Peter Green

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.

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#### Walt Boyes

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
www.controlglobal.com
blog:Sound OFF!! http://waltboyes.livejournal.com
_________________

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

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#### MAU

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

Go to http://www.bestobell.com for further details.

Regards,
MAU

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#### L.K.

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.

L.K.

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#### Anonymous

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.

Cheers!!

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#### Anonymous

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

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#### Walt Boyes

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. A #### Abhijit Goswami, Haldia 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. A #### Anonymous 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?

Have a great day!!

W

#### Walt Boyes

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

He recommended, as did I, a nuclear gauge.

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

Walt Boyes
www.waltboyes.com
[email protected]
630-639-7090

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#### Anonymous

Look at the website from Krohne http://www.krohnemar.com/Mass_Flowmeters.25.0.htm

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.

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#### Walt Boyes

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
www.controlglobal.com
blog:Sound OFF!!
http://waltboyes.livejournal.com
_________________

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

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#### Michael F. Palmosina II

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.
[email protected]

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#### Duncan MacDonald

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?

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#### L.Kolbert

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.

L.Kolbert

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#### Walt Boyes

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.

Walt Boyes
Editor in Chief
Control magazine
www.controlglobal.com
blog:Sound OFF!! http://waltboyes.livejournal.com
_________________

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

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#### Alex Kulik

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

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#### Jon Buchanan

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 http://www.berthold-us.com

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#### Walt Boyes

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
www.controlglobal.com
blog:Sound OFF!! http://www.controlglobal.com/soundoff _________________

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