I have an application where there is a possiblity of crystals dropping out of solution in a caustic tank.

If this happens, over a period of time it is feasible that the level of the crystals may restrict the tank outlet nozzle to the pump.

Does anyone know if it would be possible to use a tuning fork type level switch to detect this interface?

Alternatively is there a better form of crystal level detection?

 

In my opinion (and my experience), crystals in contact with the forks are sufficient to switch the system. (You can switch a tuning fork system easily, touching it with a finger.) I think that crystals should be soaked, and the space between crystals engaged by liquid. You might use the tuning fork succesfully to prevent a dry run condition in the pump, placing it in the intake pipe. For your application, you could try a capacitive probe instead a tuning fork, or a ultrasonic (non invasive) level gauge placed at the bottom of the tank in order to detect crystal's presence (sound propagation is different in liquid or across crystals).

Have good luck, and excuse my speech/writing.