sensor for fertilizer

sapoleon · Mar 18, 2010

Hi,
I am looking for a sensor On-Off to detect the presence of fertilizer in a silo. The fertilizer is the material that they are preparing, and they want to check the presence of material.
The data of the fertilizer, is because the materials are nitrates, fosfates, and others, that are a bit corrosives, and they are wet, that is to say they get stuck to the walls of the silo, in a 1 to 3 mm, so I need to detect the material when is more than 3mm.
Does a capacitive sensor will do the trick?
Can someone recommend me one?

Thanks.

nonuke · Mar 18, 2010

The only thing that comes to my mind, is to use load cells. IF the Silo is empty, and the net weight is above a certain level, means you have product stuck to the silo walls.

mordred · Mar 18, 2010

or ultrasonic level sensers Banner engineering has some good ones. Are you trying to detect the amount thats stuck to the walls or the amount In the silo?

Bill Wheeler · Mar 18, 2010

Sorry, but I’m a little confused of the application. Do you want to gauge the thickness of the residual on the side walls? Or gauge the level in the silo? I’m assuming that the application is to gauge the level in the silo and that the residual is a complication to measuring level.

I would rule out capacitance sensors since the coating is of variable thickness. Plus I've had issues with calibration drift over time. A load cell, as mentioned, is a real good choice as long as it isn’t too difficult to install. Ultrasonic or Radar based sensors are also very good options as long as the face of the sensor can remain clean and distances are reasonable. I use Milltronics “The Probe” Ultrasonic Level sensors for many of my level applications and have found them to be very robust and have only had problems when condensation from very aggressive chemicals formed on the face of the sensor. They are good up to 8 meters.

nonuke · Mar 18, 2010

"so I need to detect the material when is more than 3mm"
I think he wants to know how much pruduct is in the Silo, AND if there is product stuck to the walls when this value is above a certain value.

sapoleon · Mar 18, 2010

Hi,
No, I don't need or want to know how much product is in the silo, I want to use one sensor for low level and another for high level in the silo, to know when to refilling is needed and when the silo is at full capacity.
The description is the problem I have because of the type of materials.

mordred · Mar 18, 2010

You should be able to get one ultrasonic senser mounted top downward that you can set for High and low lewvel limits (easily done if hooked up to PLC) the type you would need would depend on the height of the Silo. By mounting top down you reduce the problem of being coated. There is still some coating involved from the dust. Using a wide cylindrical type 2" sensing area would alleviate some of this problem. The other advantage is that Ultra sonic seners are typically fully enclosed for the sensing circuitry so will be easy to find one thats also explosion proof as your dealing with Fertilizer this is a huge consideration

mordred · Mar 18, 2010

http://madisonco.thomasnet.com/item...-range/u3-45c2?&seo=110&bc=100|1117|1111|1067

heres one for 60 feet it has a 4-20 ma output so with a PLC you can use this signal to control your application or get continous level %

mordred · Mar 18, 2010

http://www.gillsensors.co.uk/content/datasheets/bulk.pdf

this type may be more suited to your application

Coolerman · Mar 18, 2010

I work with companies who deal with silos full of hot (up to 340 F )sticky asphalt. The only sensors they have found which are capable of withstanding the environment long term, are paddle wheel sensors. All others eventually get coated with condensed hydrocarbons and become useless. These sensors put out a constant signal while the paddle rotates. Once the material fills up to where the sensor is located, the paddle stops spinning and the signal stops. Very simple, and very reliable. The paddle wheels only have to be cleaned once a season.

Eric Nelson · Mar 18, 2010

Coolerman is right. If you just want a single-point level sensor, the motor-driven sensors work great. I use Bindicators, but there are others.

-Eric

sapoleon · Mar 18, 2010

Hi Again,
Thanks to all for your replies. I will be checking my options now, and what can I find here in Argentina.
I´ll let you know if the proyect get done, and how

Coolerman · Mar 18, 2010

Hey Eric,
I knew there was a brand name for those but I could NOT think of it when I was typing that response.

sensor for fertilizer

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