O-ring and gasket seals in water tight enclosures

[leonhart88]

Hey All,

I was looking at some IP rated enclosures and noticed that almost all of them (whether they used a gasket or an o-ring), have a raised lip on the mating side of the enclosure which compresses the gasket/o-ring.

For example:

http://www.rapidonline.com/pdf/30-4336.pdf

Is there a reason why these enclosures are designed this way as opposed to a flat face seal configuration? Does this actually provide better sealing, or is it used so they can have the o-ring/gasket further recessed in the groove to prevent it from falling out?


Thanks!

 

[Compositepro]

That is a basic sealing principle. The effectiveness of a seal depends on the peak contact pressure at every point along the seal. The raised lip creates a small seal area so the a higher contact pressure can be created using less force. The higher pressure also creates more deformation of the elastomer so that it can conform to lips that are less flat (or straight).

True O-rings seal against flat surfaces. You are talking about a gasket, even though it may be made from a round tube or foam rod.

 

[leonhart88]

Thanks Compositepro. I couldn't find any info regarding this particular configuration in o-ring design guides, so I was curious.

I don't mean to be pedantic, but isn't an o-ring just a specific type of gasket?

I assume the enclosures are designed this way so they can achieve a seal with minimal force required from the screws. I'm also guessing that at higher operating pressures, this design is undesirable because of the small sealing surface area?


Thanks!