Lime slurry density meter

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mechanation

We are trying to measure density of our lime slurry which approx 22% solids, 130 F, 2.5 gm3 density and 160 GPM flow rate.

We've looked into different options such as

Nuke density meter
ultrasonics
Coriolis
Vibrations

I'm curious about SCIAM density meter though, I was wondering if anyone have tried it already.

Please give some valuable feedback
 
Vibrating element density is a good approach for slurries but care to be taken over the % and the abrasion.
It depends on the pipe size, flow rates and if the slurry is abrasive or not.

Now, while coriolis can measure density by the same resonant frequency method, not all are as accurate as you would like so that is the first thing to check.

But they suffer from being twin parallel tubes and often of complex shapes which makes them vulnerable to erosion after the bends.
There is also a problem that if solids can settle out in the tubes that the flow will become unbalanced. This can happen even in quite high net flow if the flow is for some reason restricted in one of the tubes which creates more drop out.

On the other hand the insertion density forks can be very effective even in abrasive slurries when properly installed and they are comparatively inexpensive and can be installed into large diameter pipelines.

The tuning fork design is especially good as the forks are spark eroded from bar stock and if erosion occurs, they can be simply field corrected by adjusting the Ko offset value.

I have seen one come back from chalk slurry in a quarry to cement kiln application (chalk plus bits of flint etc. and some large hard objects.....) which was only sent back because it had been hit by something large, heavy and travelling very fast which bent one of the tines and shifted the calibration in a major way. It was otherwise still working (this was actually the version to measure viscosity as well as density and used for the control of a viscosity modifier - by reducing the viscosity they could maximise the solids content).

Otherwise, many slurries historically use gamma ray sensors.

Not too much known by me about the SCIAM except it does feature in these posts somewhere from before they disclosed the method they used. This is now disclosed and there is a wiki page on it. http://en.wikipedia.org/wiki/DM3_Density_Meter

The main point from the wiki page is, I'd suggest, the accuracy.... "Operates at < ±0.5% full scale accuracy with values repeatable to ±0.1% full scale". This isn't exceptional.

PS the wiki page suggests that other sensors may be vulnerable to noise/vibration.

"Until now, the most critical problem with traditional density measurement systems is the effect of externally induced vibration and media noise...."

This is not a problem with tube and fork density meters as they tend to operate at around 800 to 1200Hz and are pretty much immune. The frequencies to worry about are usually in the 0-100Hz band which includes lots of motor noise etc. and which propagates over longer distances with less attenuation than higher frequencies and thus cannot intefere with the high frequency of operation tuning forks. and tube density meters. Coriolis meters can have some sensitivity depending on type and manufacture (but they were most vulnerable to noise when they operated at mains frequencies and were unable to measure density).

Indeed, the fork sensor is even Lloyds (DNV etc.) approved for enclosed machinery space on board ships i.e. the engine room where there is a very high level of high amplitude vibration.

A vibrating element tuning fork will give you +/-1kg/m3 which is 1 kg/m3 in 1000kg/m3 (e.g. Water) whereas 0.5% is 5kg/m3 and this is of full scale, not an absolute error.

So you need to know if the Sciam will be accurate enough for your application.

As with any slurry application you will want to avoid a by pass installation even though a great many tube density meters were supplied for china clay applications, they were necessarily by pass installations and this would probably be the case with coriolis if you are in anything above 2" lines or are prepared to pay the price for large coriolis meters.

By pass installation may require trace heating for winter operations adding to the cost.

In the end the key china clay producers in the UK made the transition to tuning forks for direct insertion into any size pipeline as they were cheaper to buy and much cheaper to install.

But in a main pipeline or in a by pass, the problem is to ensure the flow is sufficient to keep all the solids moving and reasonably homogeneous for any sensible measurement.

Even when using a flow through device like SCIAM if the material builds up on the bottom of the pipe run then the measurement may be affected. If you want to explore this device further you really need to talk to the manufacturers.
 
I heard that the SCIAM DM3 project was pulled back, with all efforts being pushed to a newer, more industrialized design. I believe the density meter that will suit your needs (non-nuclear, real-time) is called a MassExact.

The website for this density gauge is www.directdensity.com

Th biggest issue I have with probes or forks is that they are subject to whatever is flowing through the piping system. If a small chunk of something (flowing fast enough) makes contact with the fork/probe, the reading is skewed as well as damage to the equipment may ensue.
 
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