I'm trying to find a low cost 24VDC sensor that will go active when the level of sand in a vertically mounted water pipe goes above the level of the sensor. I basically want to open a valve at the end of the pipe when the sand accumulates above a certain level in the water pipe.

 

Keyence has a fiber optic photosensor that uses the difference in light refraction in a liquid medium to activiate. If the sensor were covered in sand, in theory, the refraction would not be the same, and you could trigger off of that. I would get a distributor to let me test this theory first. Most are pretty good about letting you set up a mock-up of it and try it out. Some will even do the testing and mock-up for you.

The fiber optic portion is part# FU-94C. Use whatever fiber optic controller is appropriate for your needs.

If this turns out to be cost prohibitive, and the clarity of the water allows, use a fiber optic thru beam sensor from anyone. Mount the emitter a few inches directly above the receiver. When the receiver gets covered in sand, the sensor will activate (if set to dark operated), and you can open your valve. Make sure to use some sort of sheath to protect the fibers from the sand. The FU-94C is sheathed.

Hope this helps!

--Joe Jansen
ICQ# 39 182 450

 

there all types of solutions for this problem, you could go with pressure, ressitance, capacitance, conductivity or even ultrasonic.

How long does the sand take to fill up the pipe?

I would just use a timer relay and open the valve every hour or 2 hours, or 10 minutes or what ever it takes. I have seen this done in the water industry at wells and since there was no way to know for sure that sand was being introduced, it was simpler to just open the de-sanding valve every few hours for 5 or 10 minutes and flush the system, either way your going to lose some water and this way your sure of your system remaing clean. If the sensor fails you will build up sand and not know it, plus a timer relay is very cheap and you don't have to do any addional programming, just wire it in, set the timer interval and go home in an hour or less.

matt hyatt
technical consultants
[email protected]

 

If the other two suggestions are not useful for you, you should contact Endress+Hauser, http://www.us.endress.com, they have a specific switch for sand-under-water detection (it is a special version of the solid level switch Soliphant FTM30)

Daniel