Where to get flat o-ring for ball lock gas in?

danotts · 06-15-2008, 01:40 AM

I'm currently taking care of some issues that caused me to lose most of a new 5 lb tank of CO2. One issue I found was compression damaged flat o-rings inside my ball lock gas in connectors. Once I unscrewed the back to remove the spring valve, there is a flat o-ring around the plastic threaded part. This is the source of the leak in my gas in ball lock connector.

I went ahead and bought a new gas in connector at my LHBS today for ~$6, but when I asked if they sell the replacement flat o-rings, they said you can't get them. Does anyone know a suitable replacement? I tried a "#14" round o-ring that I got from Lowe's, but with the faulty gas-in, it did not seal it up. I didn't try it on the new connector though.

Does anyone have a solution to sourcing these parts? I'm going to look at McMaster Carr to see what I can find.

The dimensions I measured for the new flat o-ring were:

14 mm O.D.
11 mm I.D.
1.7 mm width
1.3 mm height.

(I know the math doesn't work out exactly for these dimensions, but if you've ever tried to measure an o-ring with calipers, you'd know how hard it is.)

Thanks!

Professor Frink · 06-15-2008, 03:23 AM

Midwest sells an O-ring kit which looks like it has all the O-rings on the keg:
http://www.midwestsupplies.com/products/ProdByID.aspx?ProdID=4889

jay075j · 06-15-2008, 03:29 AM

i bought them from morebeer.com

danotts · 06-17-2008, 12:20 AM

McMaster Carr sells a 14 mm O.D., 11 mm I.D., 1.5 mm thick silicone o-ring.

part number 5233T37

$9.75 for a pack of 50.

However, I'm not sure that the original o-rings/gaskets are sized appropriately. For the part from CM Becker that I am concerned with, the male threaded part has an O.D. of about 10.6 mm where the gasket slips on. The I.D. of the main ball lock fitting where the gasket rests is 15.1 mm. If I were using a round o-ring to make this seal, I would go for something like:

part number 5233T54
O.D. 14 mm, I.D. 10 mm, 2.0 mm thick, silicone

$10.13 for a pack of 50

I opt for silicone because it doesn't oxidize, which is what causes rubber o-rings to get leathery and not seal.

Now, addressing the failure of my gas-in, I've observed the following issues:

1.) The male threaded part that holds the valve in has "bow" in the flange that is supposed to hold the gasket. This may have come from stress relaxation in the plastic over time under the pressure of the gasket, or it could be a molded-in defect (warpage). Since this flange comprises 1/2 of the sealing surface, if it cannot achieve intimate contact with the gasket, all bets are off.

2.) The main gas in connector, in the interior female threaded part, has a "lip" where the gasket is supposed to seal. This caused the compression set damage to my gaskets. This is a defective part, either due to a defective mold design, improper mold assembly, or mold tooling not built to design. This interior flange should be flat in order to make a good seal with the gasket. It is not. The new connector I bought does not have this.

3.) The gasket does not center accurately on the male threaded part. This is because the I.D. of the gasket is larger than the O.D. of the male threaded part, near the flange where the gasket rests.

Attached are some pictures. I am still thinking about what the most economical, practical solution is to this issue. These connectors are used widely throughout the homebrew community, mostly without issues (I assume).

Bowed male threaded part.

Lip on flange inside main connector

Compression set o-ring due to lip on flange

Rhys79 · 06-19-2008, 12:08 AM

From having worked in injection molding, that looks like a defective part that slipped past the press operator and QC testing. The male end looks like a short fill, not quite enough plastic made it into the mold, or their was an air pocket that caused a slight edge defect where it's bowed.
-edit- On closer inspection, it actually looks like it didn't quite cool enough before the press kicked it out, and the plastic set in that slightly bowed position... It does not look like a defect in the mold itself.

The lip in the female side looks like it's part of the mold design. Why, you'd have to ask the guy that designed the mold. If it was something that was found to cause a decent amount of defective units, they would have changed it, so it's not likely the root cause of the problem you're having.

That male end should definitely have been rejected by the press operator though, it appears to be well out of spec. Then again, what can you expect from someone who makes peanuts to stand in front of a big machine and basically do little more than open and close a sliding door all day (or pickup the parts from a bin, depending on the press). If their lucky, they might actually get the entertainment of having to remove flashing or maybe partially assemble the parts the press kicks out too...

Basically, your best bet is just to call it a loss and replace it. If you just bought it recently, I'd take it back to where you got it and tell them it's defective and ask for a replacement.