Density Measurement


Thread Starter


Hi everyone,

any equation that I can use to measure the density of slurry (sludge) in pipe line? I have two unknown in the equation D=m/v, density and mass flow rate, so any other way or idea please?

Thank you, Looking forward to hearing from you.

You are being too vague, there are many ways of measuring density but no way I know of to calculate the density without first measuring something.

>any equation that I can use to measure the density of slurry
>(sludge) in pipe line? I have two unknown in the equation
>D=m/v, density and mass flow rate, so any other way or idea


Are you wanting bulk density or solids concentration?

Solids may be very close to water density so a 10% concentration may have a bulk density of 1.1. this misnomer of density for solids concentration is longstanding.
hi thank you for your reply, well, I am trying to measure the density of sludge in pipeline (the concentration) its around 8% maximum so around 80g/l. I've been advised to use Coriolis sensor its ok but still expensive. I was looking also to use differential pressure transmitter but it will not work in pipeline measurement, but in tank yes we can, ultrasonic sensors expensive and not accurate.

so I am trying to find an alternative to measure the density of the sludge and I will be grateful if you could help me with that.

Thank you very much for you help



The solids in the water may be 80g/l but the density of the solids may vary a great deal.

Are you pumping garnet, potatoes, Fat, or biosolids? If any of the latter the bulk density may be 1.02 or 0.95. The type of meter you use depends on type of fluid, not its "bulk density". If you want concentration use the term concentration.

Is the pipeline a solid steel pipe or something plastic like HDPE.

If it's plastic you could just weigh a section then work out the density from Volume assuming the line is full.

Is the pipeline vertical or horizontal?
You can measure density in a vertical line using a DP cell

Nuclear is the most accepted method for slurries.
Hi Roy

Thanks, and yes I can use a plastic section. I can add it to the line of the machine, but still I didn't get you how to measure the density of the sludge even if I could make the line plastic and vertical.

thanks again and I am looking forward to hear from you more specification.

appreciate it
I assumed the line was horizontal.

Weigh a section of line Density = weight / Volume
I'm not saying it would be easy. The line would probably want to whip around but with a good filter.

If the line is vertical just use a DP cell with the tapping points. say 1 meter apart, flush lines with water
When the SG is same as water DP = 0 mmWC
If the line SG was 1.1 the DP would be 100 mmWC

Excuse my change from Density to SG. It's easier to visualize. I'm not saying this works great, but I've seen it done in a mining concentrator on the cyclone feed with lots of small rocks in the line and around 50% solids by weight.
Hi Roy,

thank you for the information and I would like to add this to clarify more about our process. The line is horizontal, if I weight the section and calculate the density, how can I find out the change of the density throw the pipe (we discharge the sludge using a pump?

one more thing I might measure the density of the sludge before the discharge line in a hopper, but I am thinking its not constant level also its feed-in and feed-out. so is it still possible to using DP in this case? imagine its a small tank the distance between the two taps about 80cm and the sludge is coming in and pumped out.

Thank you very much and please if its ok to contact you that will be great. below is my Email

[email protected]
One option would be to use microwave transmitter. The output is in dry solid content. If you have a correlation between dry solid content and density, then the output may be converted to density. Microwave instrument is supplied by Berthold and Pro-M-tech and are quite common in the sugar industry.