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Sealing a sphere

Sealing a sphere

Sealing a sphere

(OP)


I am working on a design where I need to seal a sphere. The sphere shall pivot in one plane with relatively small tilting angles. The wet side is a corrosive and dirty environment and it is highly critical that no seepage of occur between the wet side and dry side. My initial ideas are to seal the sphere with either o-rings or some type of lip seal. My question is what sealing solution would be appropriate for this type of design?

RE: Sealing a sphere

What is the pressure on the wet side? A conically shaped seat would be the route I would take depending on the pressure you have on the wet side. Similar to a ball check valve.

RE: Sealing a sphere

why is this any different to a ball valve?

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RE: Sealing a sphere

Any plane intersection with the ball will be a circle. Design the seal gland at that circle, it defines the seal line of contact.

Ted

RE: Sealing a sphere

(OP)
Dear all,

Pressure will be around atm as this component will sit around slightly above or below the waterline. A cylinder will be attached to the sphere on the dry side and the rod will pass thru the sphere, the use of the sphere as a attachment point will reduce any side forces acting on the cylinder rod.

I am looking into the use of a machined polyurethane seal as I don't have any restrictions regarding temperature but only restrictions in terms of sealing function and its ability to withstand abrasion.
With the same type of thinking as hydtools provided that "any plane intersection with the ball will be a circle" a radial lip seal should be able to provide a sealing function. But one conundrum that I have is that the radial lip seal needs a fine surface to seal against, given that the environment it will be in will ultimately ruin this surface in terms of its roughness as dirt and growth will compromise the surface finish. Would a wiper seal mitigate this problem?

RE: Sealing a sphere

Would it be permissible for some grease to leak to the wet side ?

How are you fabricating/creating the spherical "hole" the sphere live in?
I'm guessing two hemispheres bolted together.

IF so there is are multiple opportunities for O-rings or similar seals in each half housing. The ones closest to the wet side would best be considered "wipers" so might be best made of an abrasion resistant material. Urethane etc.

I'd provide a grease hole between seal 1 and 2, and Weep holes leading to a catch can between the second and third first few.

Like others said, would a commercial ball valve serve the purpose? Maybe with upgraded seal materials?

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