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Fluid & Pressure application question. HELP!

  1. Mar 3, 2013 #1
    I have a small cylinder forcing a liquid up a 2.5mm inside diamter tube against gravity.
    The cyclinder is driven by a stepper motor and software.
    I have a problem, though outside my experience. (I am an electronic eng.)
    I need to seal the top of the liquid column, as it rises and falls, from the air by some sort of seal, driven up and down with the liquid level.

    As the liquid has a tendency to 'wet' the PTFE tube, it will also function as a sort of 'scraper' to prevent wetting all the way up the tube and to keep the liquid together in one column. The liquid is genearlly non-reactive but oxidises slowly, thus the seal needed.

    I have tried small rubber balls but I think my size tolerance is too low and its jamming the system. Bit like holding a flywheel with one finger then trying to start the motor.

    I'm now thinking micr-o-rings on a spindle seems the most easily engineered but now Im getting lost in the physics.

    Any suggestions from anyone would be appreciated. Don't really know where to start.
    Elasticity, friction etc, to many variables.

  2. jcsd
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