Hello!
I am making a bulkhead system but these do not have an O-ring groove and as I show in one of the attached photos, when you squeeze the O-ring it leaks, so I was thinking of using a flat gasket made of a material like PTFE, for example. , I would like to know more about the advantages or disadvantages or recommendations for using a flat gasket since all the systems sold by BlueRobotics and other manufacturers use O-rings.
Thank you
Hi @jua123 -
O-rings work! This link provides some background, but generally gaskets cannot seal against the high pressures that a properly-designed o-ring seal can. Machining a groove under your bolt head with a lathe should be possible!
Thanks Anthony, I had read that page before publishing but it talks about pressures of 5000 psi which is 300 bars which is 3000 meters deep, the o-rings are the best option without a doubt but in order not to work/spend above the needs of this project, I would like to know if what I am going to need it for, which is 100 meters deep, would there be any other contraindication apart from the pressure to be able to use flat joints, I really like the option of machining with a lathe but I don’t want to waste time on it if I can fix it with a simple gasket.
-Do I have to avoid using flat gaskets?
-Am I going to be safe and try to machine the nut to house the O-Ring or with the specifications of 100 meters depth, will a flat gasket of a suitable material be enough?
Thank you!
An O-ring must be in a groove that limits the compression to about 20%. Look up Parker O-ring for guidance. Dimensions are fairly critical.
Too much or not enough compression will leak. Maybe you are using the wrong size.
The hydraulics industry uses them to pressures of thousands of psi. Call up a hydraulics shop for advice.
That’s why I say about using a flat gasket, it’s clear that with a groove and the correct dimensions like the ones BlueRobotics uses for its components I wouldn’t have this problem, that’s why I’m looking for an easy and economical solution, if possible.
Thank you
Hi @jua123 -
I think it will come down to what pressure you can achieve in the gasket, without squeezing it so hard that it slips out from under the head. Assuming both the bolt underside and surface you’re sealing against are smooth and maybe lightly coated in silicone grease, this pressure between the materials will allow water through if the water is at a higher pressure. I think in your case, only testing will determine feasibility, but I’ve never seen a gasket-style seal work at depths of more than a few meters… definitely not 100m!
With that answer I will definitely try machining a slot for an o ring.
Thank you!
Hello!
Thanks for responding, I have used this type of seal on medium pressure air connectors (20 bars) and they work https://products.swagelok.com/en/c/gaskets/p/SS-4-RSD-2V
I see that you know a lot about underwater issues. Have you tested this type of seal in water at a depth of 100 meters?
Thank you!!
This kind of seal are used on high pressure hydraulic systems, so, if properly used, your good to go down at least to 2000m ! 
