Fluid & Pressure application question. HELP

[Momekric]

Hi,
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 I am 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.

Iain

 

[Achy47]

Hello Iain,

Thank you for reaching out to us for help with your project. I can offer some suggestions for your seal design.

One option could be to use a flexible membrane as the seal. This could be made from a material such as silicone or rubber, which would be able to conform to the changing shape of the liquid column as it rises and falls. The membrane could be attached to the top of the cylinder and would move up and down with the liquid level, creating a seal between the liquid and the air.

Another option could be to use a series of small rings, as you mentioned in your post. These rings could be made from a material with low friction, such as PTFE, to prevent jamming. The rings could be attached to a spindle that would move up and down with the liquid level, creating a seal at the top of the liquid column.

In terms of the physics involved, elasticity and friction will definitely play a role in the effectiveness of your seal. It will be important to choose materials with the right properties to ensure a tight seal without causing too much friction that could hinder the movement of the liquid.

I hope these suggestions help in your design process. As always, it's important to test and iterate your design to find the best solution. Good luck with your project!