7 replies to this topic

[6Gill]

O-rings are a very simple and often ignored till it's to late.Hopefuly basic information might help save your dive esspecialy if your away on vacation.

There are two types of o-rings...STATIC which are found on port plugs/hose ends and DYNAMIC which are on moving parts such as SPG spools. DUROMETER is the scale used to measure the hardness of the o-ring and the common range is 70-90(70 being the softer)The softer o-rings seal better but don't last as long esspecially DYNAMIC o-rings.

A variety of material is used...NITRILE(rubber) is the cheapest and usually black.VITON is usually brown and considered the one to use in a oxygen or nitox enviroment.The other ones you might see are EPDM which are usually purple. Color by itself is not an indicator of the material.

The shelf life of o-rings is about 5 years and they brittle with age. To lubricate your o-rings use a silicon(DOW111) which is not O2 compatible or Christolube MCG111 which is rated for O2 use.A little goes along way,the o-ring should have a shine like it is new without being able to see the lube.

Avoid over tightening as this crushes the o-ring and possible distorts them causing premature failure and leaking.The o-ring works by 'flowing' into the groove.To tighten...finger tighten the hose then with a wrench turn 1/8-1/4 turn.If using a yoke reg do not overtighten as this doen't make it seal better,if the o-ring is leaking replace it.

If the connection has loosened off there is a chance of extrusion,DO NOT just tighten down the loose part. Remove the part,remove the o-ring and examine it,replacing if neccery then tighten down properly.

To remove/replace o-rings use a soft tool with a rounded end to protect both the o-ring and the seating surface.A magnifying glass is nice addition with which to examine the o-ring/seating surface.

Here is a list of common sizes but yours may vary...

003 SPG spool
011 3/8" hose/port plug
012 7/16" SPG hose/port plug
014 'Thin' reg to yoke
111 small DIN reg/valve
112 'Thick' reg to yoke/standered DIN reg/valve
214 tank neck 3/4"

[Dennis]

Eric,

Very good. Most people do not know very much about o-rings. Interestingly enough, you can get some replacement o-rings from your local hardware store in the plumbing department (they are usually Nitrile o-rings). Take the old one and compare sizes because the size number on the package at the hardware store is not the standard size that you have listed. The OD and ID are usually on the package.

Can't find 003 o-rings at the hardware store, just too small.

[Dive_Girl]

6gill - this is a great post! I'm going to print this out and put it with my save-a-dive kit to go through this weekend!

[Dive_Girl]

Had to find this post again - I'm headed to the dive shop to resupply the dive-kit. I am almost completely out of various o-rings!!

[ScubaDadMiami]

Interestingly enough, you can get some replacement o-rings from your local hardware store in the plumbing department (they are usually Nitrile o-rings).

I have been told that hardware store o-rings are not made the same way as those for the scuba industry, and that they are not nearly as durable. However, I have bought some from the hardware store for other diving uses (so that my knife can swivel inside of my light handle), and they seem to be holding up just fine. Can anybody say one way or the other about whether there is a difference in the quality or method of construction?

I am not certain. However, I seem to recall the Oxygen Hacker text also mentioning not to use hardware store o-rings for scuba gear (beyond the oxygen service issue).

[Desert_Diver]

I seem to recall the Oxygen Hacker text also mentioning not to use hardware store o-rings for scuba gear (beyond the oxygen service issue).

The problem with hardware store o-rings is that you don't know *who* made 'em, what they're really made of, or the hardness/durometer. Like you, I might use one in a non-critical location, but that's about it. And yeah, there's absolutely a difference between the quality from different vendors! A friend of mine is a mechanical engineer in the semiconductor processing industry, and he'd *never* use an unknown off-the-shelf o-ring.

FYI, here's the link to the Parker O-ring Handbook, pretty much an "everything you wanted to know about o-rings but were afraid to ask":
http://www.parker.co...ure/ORD5700.pdf
linked from their general literature page at:
http://www.parker.co....asp?cmid=3903

and if you want to find a local distributor, hit
http://www.parker.co...ish/indexv4.asp
and click on SEALS (submit), UNITED STATES (submit) O-RINGS & MOLDED SHAPES and then select your state and hit the (submit) again.

Parker's V1260-75 FKM line is equivalent to an 80 durometer Viton, so it's about split between the softer 70s used in low-pressure and static seals, and the 90s normally used in high pressure or dynamic scuba seals. That's what I've been using for a few years, and I haven't had a problem with it. However, I'm *not* a certified reg technician, just an electronics jock that can't keep his fingers out of his toys.

[ScubaPunk]

And Why is this the first time I am hearing all about this???? Sounds like maybe something they should have mentioned to us in OW. I never heard anything like this in OW or AOW. Is this common sense kind of stuff that we're just expected to know?

6Gill -

[fbp]

Also, as a foot note, you can order these from on line O-Ring mfg...

I did for my camera housings, got tired of paying $8+ for one O-ring...So did a quick search, inquired and sent a sample of an old one to the shop and I now have 10-25 (bulk makes sense here) for about the same price of 2 "Boutique" rings... can't remember the pricing but believe $.15 to $.80 for the big ones. 10 for $8.00 or something like that.

Just send a sample in an envelope and they'll match it up..

I didn't specify what they would be used for, UW Photo housings etc... 2 years and no problems...
So I'm a happy camper here...

Not sure which ones I got it from, believe the Los Angeles one:
http://www.oringsusa.com/

http://www.air-oil.c...sonlinefset.htm

Edited by fbp, 12 May 2006 - 06:52 AM.