o-rings for foster fittings

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delooper

delooper

Member
Jul 7, 2020
1,357
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Duncan, BC, Canada
I recently had an o-ring for a foster fitting fail -- in the female 1/8" BSPP fitting in the image below.
PXL_20220728_045653821.jpg


I did some searching on the forum and all the advice was for buna-n AS568-10 o-rings.

But I have some of those, and they're far from what I need. My o-rings need to be 3/32" thick, but the -10 o-rings are 1/16" thick.

So I ordered some -105 and -106's. Probably both of them will do the job but hopefully I'll discover what the proper o-ring size is for my foster fittings.
 
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Standardized as568 series (not metric) o-rings have 3 numbers in their 'dash number' callout, with the 1st number denoting the series cross section. The second 2 numbers together is just a 2-digit lookup number that picks one of a group of predetermined inside diameters (ID's). The actual ID's do not correspond to the lookup number. You literally have to look it up in a table to see the sizes for a specific dash number o-ring.

-0XX = 0.070" cross sectional diameter
-1XX = 0.103" cross sectional diameter
-2XX = 0.139" CS dia
-3XX = .210"
-4XX = 0.275"

Since you know you need 3/32" cross sectional diameter, that is the -100 series, with -1XX dash numbers.

Here are the first few dash numbersfor that series from a table I have. You should be able to match up the ID and complete dash number from the old ring:

SERIES 1XX .103 DIA
GL WIDTH .140
DASH#, ID(in)
-102,0.049
-103,0.081
-104,0.112
-105,0.143
-106,0.174
-107,0.206
-108,0.237
-109,0.299
-110,0.362
-111,0.424
-112,0.487
-113,0.549
-114,0.612

GL,
Feinwerk
 
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Feinwerk said:
Standardized as568 series (not metric) o-rings have 3 numbers in their 'dash number' callout, with the 1st number denoting the series cross section. The second 2 numbers together is just a 2-digit lookup number that picks one of a group of predetermined inside diameters (ID's). The actual ID's do not correspond to the lookup number. You literally have to look it up in a table to see the sizes for a specific dash number o-ring.

-0XX = 0.070" cross sectional diameter
-1XX = 0.103" cross sectional diameter
-2XX = 0.139" CS dia
-3XX = .210"
-4XX = 0.275"

Since you know you need 3/32" cross sectional diameter, that is the -100 series, with -1XX dash numbers.

Here are the first few dash numbersfor that series from a table I have. You should be able to match up the ID and complete dash number from the old ring:

SERIES 1XX .103 DIA
GL WIDTH .140
DASH#, ID(in)
-102,0.049
-103,0.081
-104,0.112
-105,0.143
-106,0.174
-107,0.206
-108,0.237
-109,0.299
-110,0.362
-111,0.424
-112,0.487
-113,0.549
-114,0.612

GL,
Feinwerk
Click to expand...
Great post, great info, man. Thnx
 
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@Bigragu thanks man!
I used to have to design tools that used O-rings and grooves in my career, mostly simple cylindrical mating parts and vacuum seals. I learned a lot from the Parker o-ring guide. Do a Google search for 'Parker O-ring guide' to receive the holy Grail of info.

Here's a good jumping off page from one manufacturer, Parker. Open up the related documents section at the bottom of the web page for links to all sorts of o-ring information:


Feinwerk
 
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I have found that there are two type of disconnects available for two type of (foster) fittings. North American metric or EU/Asia metric.
I am usually buying these things stainless steel from Asia, but occasionally run into the differences (US vs Asaia/EU), I mark it up in the screenshot.

fittings.JPG


You can mix the fitting + quick disconnect (american made metric and EU/Asian made metric), it will lock only it will have a little play longitudinally (along the centerline). Still safe to use, the balls locking in a "jaw", try to find QD with more balls or SS at least.

I am using 6x2 or 6.0x1.5 (IDxWOD) and these fits every disconnect.
 
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bigHUN said:
I have found that there are two type of disconnects available for two type of (foster) fittings. North American metric or EU/Asia metric.
I am usually buying these things stainless steel from Asia, but occasionally run into the differences (US vs Asaia/EU), I mark it up in the screenshot.
Click to expand...

Yeah, I imagine that's what's happening. I should measure all my quick-connects to see if they're all of the same dimensions.
 
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delooper said:
Yeah, I imagine that's what's happening. I should measure all my quick-connects to see if they're all of the same dimensions.
Click to expand...
Last winter I ordered a big box of SS fittings from ali.
I have many bottles+way too many hoses with mixed threads and connectors+a 10mm threaded compressor--- and all these threads are mixed up, I have a full drawer of any kind of stupid size fitting threads and need a special attention not to mix them up.
I was planning to throw out all the NPT's and want to keep all the fittings in a single platform, that will be either BSP or 10mm.
 
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I recently had a fail. Found a random o-ring that worked for a few fills and then crapped out. Then found the right size, so I'm good now.

But I just ordered this 25 pack from Captain O-ring in case it happens again.

www.captainoring.com

Remote Quick Disconnect O-Rings (25 Pack)

Captain O-Ring is a leading supplier of o-rings, rubber seals, and all custom rubber parts. We specialize in short lead times, quality product, and custom orders small and large.
www.captainoring.com
 
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