Level sensor for low density, under pressure
Level sensor for low density, under pressure
(OP)
Hello,
I'm looking for a sensor that could measure the level of a tank containing polypropylene beads (solid). Those beads have a density of approximatly 1 pound per cubic foot and the tank is under pressure between 60 and 100 psi.
The tank itself is made of metal (probably steel) and we suspect the inside was coated to avoid friction and rust. It's a cylinder: about 5' diam, 13-14' high
We presently use a low level probe that is like a fork. When there is no more beads between the metal bars, it activates. But because of the static electricity that builds up, it's not always working well (even though we try to eliminate as must static as we can). And operators would like to have a real time measure instead of just low level.
I saw ultrasonic sensors that could be interesting, but will they work under that pressure and with that low density?
Any other possibility?
Thank you!
I'm looking for a sensor that could measure the level of a tank containing polypropylene beads (solid). Those beads have a density of approximatly 1 pound per cubic foot and the tank is under pressure between 60 and 100 psi.
The tank itself is made of metal (probably steel) and we suspect the inside was coated to avoid friction and rust. It's a cylinder: about 5' diam, 13-14' high
We presently use a low level probe that is like a fork. When there is no more beads between the metal bars, it activates. But because of the static electricity that builds up, it's not always working well (even though we try to eliminate as must static as we can). And operators would like to have a real time measure instead of just low level.
I saw ultrasonic sensors that could be interesting, but will they work under that pressure and with that low density?
Any other possibility?
Thank you!





RE: Level sensor for low density, under pressure
Contact a few vendors and see what they say.
xnuke
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Level sensor for low density, under pressure
RE: Level sensor for low density, under pressure
You may also look into electro-mechanical type level instruments.
Good luck.
RE: Level sensor for low density, under pressure
The load cell could be a solution (you mean measuring the weight of the silo to know it's level, right?). But there are several pipes connected to the silo and I'm not sure how this could affect the readings. I'll try to get more details about that.
I searched the Internet and contacted several vendors and one technology seems interesting. It's the laser level measurement. The vendors should come back with more details about that.
Thank you for for your answers!
RE: Level sensor for low density, under pressure
The Radar Instruments to day are totally different from those 2 or 3 years ago. Guided Radar has an antena inside the tank and works better then the old radars.
Contact Magnetrol, Rosemount (Emerson), K-Tek,
ilan
RE: Level sensor for low density, under pressure
RE: Level sensor for low density, under pressure
It was in fact only last year. It was guided radar.
The problem they faced is that the dielectric constant of the material is about 1.02 (almost the same as air).
The technical datas I saw on the internet said that the guided radar technology required a dielectric constant at least around 1.5 - 1.6
So I think we can forget that option :(
Measuring the weight of the silo could maybe be done, but the silo is going up to the ceiling, there is almost no room if we want to add someting under it. And i'm not sure if it would me precise enough anyway. The material in a full tank weight about 120-300 pounds (I learned that the density can be as low as 0.6 pound per cubic foot and as high as 2 ppcf!). I don't know how the tank itself weight, but it is probably considerably more. The measure would need an maximum error of a few pounds.
The vendors that I contacted seem to have difficulty solving that problem too. A couple of them asked for samples to make more tests.
RE: Level sensor for low density, under pressure
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RE: Level sensor for low density, under pressure
Which raises an interesting question. How level is the sample? Is there some process by which the beads are actually leveled?
One possibility is to use a laser with some sort of scanning system so that more level samples are collected and averaged or otherwise processed.
Ultrasound should work, but you'll need to have a reference distance to calibrate against in the chamber
TTFN
RE: Level sensor for low density, under pressure
The ultrasonic sensors I've seen up to now would be great if it wasn't their low resistance to pressure. This technology doesn't seem to be adapted to that kind of environment.
Someone suggested me an admittance sensor. http://www.drexelbrook.com/products/Sku.cfm?sku_Id=12038&GO.x=16&GO.y=8
But since it's reading is based on the dielectric constant of the material, I wonder if it would be precise enough to distinguish the beads from the air.