Anyone have experience designing an asymmetrical o-ring groove under a bolt head?

[designnewb]

I am looking for any info on how to design an asymmetrical o-ring groove under an M10 bolt head. I've already chosen the O-ring size. It's I.D. is 10.03 +/- .13 & it's section width 1.02+/-.08.

I want to make sure the groove accounts for the o-ring stretch round bolt. The Parker O-ring handbook seems to have info regarding squared gland dimensions based off your o-ring size. I need info on an asymmetrical grooved gland. Am I making any sense?

See attached pics for bolt drawing and example of what I am trying to come up with (i.e.self-sealing fasteners)and the sketch of the groove I have so far.

 

[electricpete]

I can't help but some questions/thoughts that come to mind:

1 - Are there provisions in place to ensure the bolt is not rotated during assembly?
2 - Aren't you reducing the load-bearing area under the head of the bolt?
It seems like maybe an option would be a washer under the bolthead and a bigger diameter o-rinig / groove so you don't have to worry about the radius of the bolt head.

feel free to ignore me if it's not relevant

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(2B)+(2B)' ?

 

[byrdj]

have you looked at iso 6149-1.

http://www.zeroleak.com/spec_drawings/metric_ports.html

can your design be changed so the space for the oring is in the "nut" side?

 

[tbuelna]

Two things to consider with your groove geometry:

First, the groove shape should only produce sufficient compression of the o-ring for the pressure levels it will be subject to. In general, for static seals lower pressure should require less installed compression of the o-ring. And keeping installed compression to a minimum is usually better for the o-ring. Attached is a chart that shows flattening of an o-ring cross section due to circumferential stretch.

Second, as a rule of thumb, the o-ring volume should be no more than 80% of the groove volume.

Hope that helps.

 

[IRstuff]

One thing you'd have to be careful about is abrasion damage to the seal from the bolt head.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529

 

[robertib]

If you have the Parker Catalog, have a look at the triangular groove details (4-21 / p101 of their 50th anniversary edition catalog). It may be enough for what you are looking for.

 

[designnewb]

Thanks everyone for their responses so far.

1 - Are there provisions in place to ensure the bolt is not rotated during assembly?
2 - Aren't you reducing the load-bearing area under the head of the bolt?
It seems like maybe an option would be a washer under the bolthead and a bigger diameter o-rinig / groove so you don't have to worry about the radius of the bolt head.

1. Yes
2. The load-bearing reduction will probably not be a factor in this design intent, but definitely something to rule out as a problem for sure...thanks for the thought. I am also looking into a self-sealing washer.

have you looked at iso 6149-1.

http://www.zeroleak.com/spec_drawings/metric_ports...

can your design be changed so the space for the oring is in the "nut" side?

No, I haven't looked into this but I am now....thanks! I don't think changing the o-ring to the nut side would be ideal for this design intent, but thanks for the thought.

Two things to consider with your groove geometry:

First, the groove shape should only produce sufficient compression of the o-ring for the pressure levels it will be subject to. In general, for static seals lower pressure should require less installed compression of the o-ring. And keeping installed compression to a minimum is usually better for the o-ring. Attached is a chart that shows flattening of an o-ring cross section due to circumferential stretch.

Second, as a rule of thumb, the o-ring volume should be no more than 80% of the groove volume.

Hope that helps.

It most definitely helped! Thanks for the info tbuelna!