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2999 (Civil/Environmental) (OP)
27 Jan 09 12:58
In this application we have sump which collects storm water. From the sumps storm water is pumped to storage vessel through a 4" PVC pipe. (From the storage vessel it goes to oil water separator.) However in situation of catastrophic failure sump could be filled with diesel fuel and will be pumped to storage vessel. We wanted to have some kind of sensor on 4" PVC pipe so that it recognize that there is no water in pipe but its filled totally with oil and it should send signal to control panel to stop pumping oil from sump.

Any suggestions? Thanks.
JLSeagull (Electrical)
27 Jan 09 14:05
Consider a small Coriolis meter (1/4-inch) for the liquid density.  This could be a bypass across any restriction.  The Coriolis meter will be metal not plastic.
danw2 (Industrial)
27 Jan 09 16:47
A conductivity probe in the fluid should readily tell you whether the fluid is water, generally 500+ uS/cm or an oil at some number probably less than 1uS.  

A potential drawback of exposed electrode probes could be coating the electrodes with oil.  The flow velocity & turbulence would have to sufficient to 'wipe' or clean the oil off the electrodes.

Torroidal probes are encapsulated, and I suspect that their sensing technology would not be affected by an oil coating, but a vendor could confirm that.
roydm (Industrial)
27 Jan 09 22:09
The problem with electrodeless conductivity, There will be very little difference between Oil and an empty pipe. Perhaps a combination of Ultrasonic Gap switch and conductivity.
Gap Switch closed and conductive = Water
Gap switch closed and Non conductive = Oil
danw2 (Industrial)
27 Jan 09 22:49
Good point, Roy.  I missed the empty pipe part.
Unotec (Chemical)
28 Jan 09 12:50
There's a bunch of oil sensors out there. I'm sure a Google search will report many

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>

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