O-ring design choices

Then there are "square o-rings" I've run across in hydraulic valve bodies. Mike
 
FanMan said:
The Parker o-ring handbook (which you can download from their website) has lots of good information on o-ring gland design and dimensions for various pressures and sealing scenarios. Start there and adjust the diameters if necessary. There are also lots of odd size o-rings besides the standard 2-xxx sizes, all listed in the handbook appendices.
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^^^^^This
 
FOMOGO said:
Then there are "square o-rings" I've run across in hydraulic valve bodies. Mike
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In the shop I worked a "Square O-Ring" was/is called a Ring Seal. Now I dont know if this is the actual designation or if it was just the term used in that shop to keep from getting the 2 different seals mixed up when rebuilding something but thats the way I was skooled.
 
Also, O ring grooves need to be somewhat wider than the O ring to allow sideways expansion when the o ring is compressed radially.
 
Latinrascalrg1 said:
kd4gij.....Thanks for sharing that info. Before i read your post I ALWAYS thought/assumed that the groove the o-ring sat in was semicircular and would have never figured square cut and are much more complicated than I ever imagined.
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The oring spreads sideways when it it compressed by the sliding member. There must be room for the compressed rubber to go to. The sides of the oring (90 degrees to the compression) must have space they can move into. A groove that just fits the shape of the oring does not allow that compression and other movements that allow the oring to make a proper seal.
 
Not to be pedantic, but solid rubber is really a liquid and hence it can't be compressed. It certainly can be deformed and this is what most folks mean by "compression". This means that the O-ring groove has to at least have the volume of the O-ring to allow it to completely deform without being torn etc.

David
 
David S said:
Not to be pedantic, but solid rubber is really a liquid and hence it can't be compressed. It certainly can be deformed and this is what most folks mean by "compression". This means that the O-ring groove has to at least have the volume of the O-ring to allow it to completely deform without being torn etc.

David
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You are correct, David. 'Compression' was not the right word. 'Displaced' and 'displacement' would have been better...
 
Bob I was just following up on your information. I have seen folks make an O-ring groove that they think is small because it will provide more "compression" When they slide the tube over it, they shear the top off the O-ring even though they thought they had lots of chamfer.

Thanks for taking it the right way.

David
 
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