O-ring groove design 2

[Prometheus21]

Hello everyone,

I'm often in a position where I have to design O-ring grooves for different compressed gas applications. Radial static installation, radial dynamic installation, axial installation, dovetail grooves, half-dovetail grooves, you name it. Trelleborg and Parker handbooks are good resources in combination with industry experience.

Now, another configuration is what I guess you can call an angled seal(?) configuration. Quick example below (blacked-out part is the O-ring to indicate placement). The groove can be both a typical "square" configuration (as shown on the image below), or as half dovetail groove. The angle of orientation usually lies between 60° and 90°.

My question is this: Does any design handbooks cover this specific configuration? I know certain standards describe specific grooves for specific O-ring sizes for these configurations (e.g. ISO 5145 & CGA V-1), but not nearly as extensively as the other more common configurations. I usually deal with O-rings with a cross section between 1.78-2.4 mm, with an inside diameter <20 mm, so the stretch range is usually a bit wider than the typically recommended 2-8 %.

Don't get me wrong, I have designed these before, with no issues, by using common sense. I'm simply wondering if any handbooks cover this topic, as I've yet to find any that does.

Thank you for any input you may have.

 

[hydtools]

The handbooks prescribe the amount of squeeze the o-ring should get and gland surface finish to seal properly. Design around that information. The gland will then become what it needs to be. Also consider the means to create the gland.

Ted

 

[Prometheus21]

Yes, that is pretty much what I gathered, guess I will just keep tabulating existing designs as I make them. The hardest (and costliest) part of the process is without a doubt the machining of such grooves, but hey, what the customer wants the customer gets...

 

[Sealing guy]

Unfortunately there are no standards for conical sealing. O-ring being round in Shape, after assembly need to have same squeeze / fill in these type of grooves too.
Only concern here, as you rightly mentioned is size selection. In these cases I would prefer to go for O-ring ID size either equal to or preferably 1%~2% larger than the lower groove dimension so when the pressure in system acts it fills the free area in groove and energize the O-ring to give good sealing.

Thanks

 

[Prometheus21]

Sealing guy:

Correct, a proper squeeze is important. Parker's recommendation of minimum 0,2 mm compression holds up even for higher pressure ratings.
Certain applications involving sealing against a cylinder valve outlet have weird standards, AFNOR NF 29-650 being one of them. The O-ring gland doesnt have enough room and the O-ring is therefore slightly extruded. This is compensated for by using 93 ShA Zurcon O-rings, as they are very well suited for these applications, and for pressures upwards to 400 bar (cylinder pressure).