Permeability issues relating to sealing compounds

[mcswe]

Does anybody have any knowledge relating to Permeability issues relating to various sealing compounds. We have a problem with water ingressing into a small vacum on one of our components (Volume in the region of 1.7x10-5 m3) . Having carried out numerous investigations all evidence seems to point to ingress through the compound used to seal the volume.
I have tried to use Darcy's Law and various permeability values given by material suppliers to calculate the mass flow rate across the seal, for different materials, but i keep coming up with unrealistic answers. I was wondering if anybody had any similar experiences or advice.
Any advice greatly appreciated.
Thanks

 

[Timelord]

Check out the Parker O-ring Handbook. I contains permeability data for various o-ring compounds.

http://www.parker.com/o-ring/Literature/ORD5700.pdf

Timelord

 

[MikeHalloran]

I'm curious about what compounds you have tried, and if you are referring to thixotropic pastes or to elastomers when you say 'compounds'.

I don't have much experience with water ingress into evacuated cavities. I do have some experience with air ingress into water under slight negative pressure in elastomer tubing. In that instance, silicone was a nightmare. Viton worked much better.



Mike Halloran
Pembroke Pines, FL, USA