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Making custom seals for an old high pressure CO2 valve?

Just a Sparky

Hot Rolled
Joined
May 2, 2020
Location
Minnesota
Just asking to see if anyone here has experience with cutting rubber and selecting the right type of it for sealing high pressure CO2.

I've got an old high pressure CO2 valve which predates the modern use of O-rings for sealing valve stems and seats. Instead it relies upon a gland type seal around the stem and a flat rubber washer which is captive within a 'cup' which seals it against a raised boss in a flat seat. OEM got bought out decades ago so genuine replacements are unobtanium. Here are some visuals to help clarify:

Modern O-ring type valve stem:
ansul-co2-valve-stem-a441004.jpg


My valve stem:
IMG_20200806_153721928E.jpg

Just wondering what my best options are going to be for obtaining replacement rubber seals for this application. The rest of the unit is perfectly good and has historic value. (Built to a special heavy spec for the navy during WW2) I would hate to have to junk the whole thing just because the seals are old & tired.

What type of rubber should I use which will play nice with high pressure CO2? What process should I use for cutting it? Some hammer-driven hole punches since all of these pieces have round profiles? Or would it be better to have some pieces laser cut from suitable stock?
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
You can also get teflon backup rings that go either side of the O ring that handle higher pressure...up to 3000psi for small dia o rings.....grease the assy with the special 3000 centistokes grease from Dow Corning....also available are various other materials in flat rings,such as poly-U ,teflon,etc......but maybe not in the specific size you want.
 

BT Fabrication

Stainless
Joined
Nov 3, 2019
Just asking to see if anyone here has experience with cutting rubber and selecting the right type of it for sealing high pressure CO2.

I've got an old high pressure CO2 valve which predates the modern use of O-rings for sealing valve stems and seats. Instead it relies upon a gland type seal around the stem and a flat rubber washer which is captive within a 'cup' which seals it against a raised boss in a flat seat. OEM got bought out decades ago so genuine replacements are unobtanium. Here are some visuals to help clarify:

Modern O-ring type valve stem:
ansul-co2-valve-stem-a441004.jpg


My valve stem:
View attachment 368225

Just wondering what my best options are going to be for obtaining replacement rubber seals for this application. The rest of the unit is perfectly good and has historic value. (Built to a special heavy spec for the navy during WW2) I would hate to have to junk the whole thing just because the seals are old & tired.

What type of rubber should I use which will play nice with high pressure CO2? What process should I use for cutting it? Some hammer-driven hole punches since all of these pieces have round profiles? Or would it be better to have some pieces laser cut from suitable stock?
find a local hydraulic shop, they can get anything if they specialize in rebuilding hydraulics or cylinders. id say any good non reactive rubber like PTFE or Buna N nitrile rubber is good.
 

petersen

Aluminum
Joined
Dec 13, 2008
Location
minnesota
I have had success machining replacements for rubber sealing elements
from PTFE. Round objects are easily lathe turned from bar stock.
Years ago I machined PTFE vee stacks in a size I could not find.
Mcmaster has now added that size to their list (9572k32) so I no longer
need to make them.
Your location is no longer identified but I remember that you are in mn.
I have not succeeded with the "new improved" private message routine.
If I had contact information we could visit.
 

4GSR

Diamond
Joined
Jan 25, 2005
Location
Victoria, Texas, USA
If you're actually going to use this for sealing CO2 gas, regular old Nitrile or Buna- N will not work. It'll eventually self-destruct from explosive decompression. Teflon, AKA PTFE, is your best bet for any CO2 application. You can get this in O-Rings as well as round stock where you can machine your own seals. But there's one problem with using Teflon, it doesn't stretch very good if at all which would make it next to impossible to install. You could skive cut the Teflon to install. Next would be HSN which is hydrogenated Nitrile. There are certain grades of Viton and Flurel that work well, too. The problem with HSN and Viton is the availability of O-rings in a small size as you are looking for.
 








 
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