Info O-rings for Divers

1: O-rings for Divers​

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Question:

“ I'm a recreational diver. Why should I care about O-rings? ”

Answer:

“ For starters, an O-ring failure could empty your Scuba tank in about a minute. ”

(Table Reprinted by permission)
This table appeared in Life Ending Seconds, 3000 to Zero in 72 Seconds, Advanced Diver Magazine by Curt Bowen

​

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“ Don’t worry. Catastrophic O-ring failures are extremely rare, as long as you know what you're doing. ”

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However, O-ring leaks aren't unusual at all, and can prematurely abort your dive or detract from an expensive vacation. Fortunately, understanding them is easy and will dramatically reduce failures. Many O-rings can be safely replaced in the field with minimal skill and are part of most Save-a-Dive kits.

You can repair most leaks with some spare O-rings, a removal tool kit, a wrench or two, and some lubricant.

What is an O-ring?​

O-rings are "resilient" toroids (doughnuts) made from a variety of materials and are primarily used for liquid and gas tight pressure seals.

Literally billions of O-rings are made every year. They come in an enormous variety of materials, sizes, colors, and shapes.

Where are O-rings Used?​

Most divers are wearing about 50 O-Rings. Here are a few of the diving-related products that depend on them:

• Cylinder valves
• Regulators
• SPGs (Submersible Pressure Gauges)
• Dive Computers
• BCDs
• Underwater lights and camera housings
• High Pressure Compressors, Nitrox mixing systems, etc
• Machinery and fittings on boats
• Commercial diving equipment — like almost everything we use

O-ring Types​

O-ring applications are divided into two broad categories; Static and Dynamic. There are so many creative applications that some can be seen as hybrids. Static simply means that the sealing surfaces are not moving under pressure while dynamic do. For example:

Static​

• Scuba cylinder to valve seals
• Scuba valve to first stage seals, DIN and Yoke
• Hose connections on first stage Scuba regulators
• The lens seal on metal-body SPGs
• Port and door seals on underwater camera housings
• Door and port seals on decompression chambers

The first O-ring that divers learn to use is usually the stage regulator connection to the cylinder valve. This image is of a DIN connector

The first O-ring that divers learn to service is often the hose to first stage regulator connections

O-ring grooves don't have to be round. This image of is an underwater camera housing. This is classified as a static pressure-seating face seal O-ring.

Pressure-seated O-rings like this one don't require robust clamping mechanisms because the pressure does the work. The four small spring-loaded latches are all it takes to compress the O-ring enough to make the initial seal.

This PLB (Personal Locator Beacon) housing has threaded caps at both ends with static piston seal O-rings. You can see the compression of the O-rings through the clear plastic tube.

Sectional view of a conical Acrylic pressure-seating viewport for a deep submersible rated for 1,000 M or 3,281' working depth. Similar ports are used for decompression chambers. The O-Ring only functions at very shallow depths, enough for the pressure to create a metal to plastic seal. ​

Dynamic​

• Cylinder valve stems
• Hose connections on second stage Scuba regulators and swivels
• Hose to SPGs and dive computer connections
• Button and rotary controls on underwater camera and light housings
• Power inflator quick disconnects on BCs (sort of a hybrid but they are allowed to rotate)
• Hydraulic and pneumatic pistons including counterbalance pistons on hatch-back cars

Hose connector to the second stage regulator is a dynamic seal. Look closely and you can see the brown O-ring in the groove under the lock nut.

The standard HP (High Pressure) hose connection that was originally designed for SPGs are also used for AI (Air Integrated) dive computer adapters and wireless transmitters for AI wrist-mounted computers. Note the different style "spools" with a separate O-ring for the hose and the mating device.​

Table of Contents for O-rings for Divers
Post 1: O-rings for Divers (this post)
[URL='https://www.scubaboard.com/community/threads/o-rings-for-divers.553724/']O-rings for Divers[/URL]

Why should I care?​

What is an O-ring?​

Where are O-rings Used?​

O-ring Types​

Post 2: How do O-rings Work?
[URL='https://www.scubaboard.com/community/threads/o-rings-for-divers.553724/#post-8116451']How do O-rings Work?[/URL]
Post 3: O-Ring Materials, Lubrication, and Maintenance
[URL='https://www.scubaboard.com/community/threads/o-rings-for-divers.553724/#post-8116452']O-Ring Materials, Lubrication, and Maintenance[/URL]

O-Ring Installation​

Material​

Lubrication​

Oxygen Cleaning and Compatibility​

Oxygen Cleaning in the Real World​

Post 4: O-Rings Buying Guide
[URL='https://www.scubaboard.com/community/threads/o-rings-for-divers.553724/#post-8116453']O-Rings Buying Guide[/URL]

Measurements​

Material​

Durometer​

Making Custom O-rings​

Pro Tips​

Post 5: O-ring History
[URL='https://www.scubaboard.com/community/threads/o-rings-for-divers.553724/#post-8116454']O-ring History[/URL]

Patents​

Enabling Technologies​

Post 6: DIY O-rings for Divers
[URL='https://www.scubaboard.com/community/threads/o-rings-for-divers.553724/#post-8116455']DIY O-rings for Divers[/URL]

Underwater Housings​

High Pressure Gas Systems​

Custom Gas Manifolds​

Custom Scuba Cylinder Manifolds​

Special thanks to the Scubaboard Moderators that helped me with this thread and XS Scuba for their technical assistance.

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Continued in the next post

 

[Couv]

Silicone grease seems to be a better lubricant than Christo lube because of the residue (drying out) I find with Christo (OK, I am lazy and I don't like cleaning it off). Nice too know you do you use silicone for 21% 0² or lower applications. For my R/R of my permanently retired scuba reg, I will use silicone.

FYI: Evidently Dow rebranded their Molykote as a DuPont product.
MOLYKOTE® technical data sheet (dupont.com)

As you advise, I will wait @rsingler to hopefully respond before I buy either MCG 111 or Tribolube.

Thanks again,
m

I'm not the genius that @rsingler is but here are a couple of threads you may find helpful.
Oxygen safe lube
Tribolube... have you tried it yet?

 

[markmud]

I'm not the genius that @rsingler is but here are a couple of threads you may find helpful.
Oxygen safe lube
Tribolube... have you tried it yet?

Hi couv,

I asked rsingler and Akimbo directly because they have answered some of my elementary questions before, I wasn't indicating that they are the only two who can give me an expert answer. So, thanks for responding and the links were very helpful.

I am assuming that you are exclusively using Tribolube now...? Are you on a 13 year run with Tribolube?

I will wait for rsingler to respond. But, if he doesn't feel like responding, eventually, I will just buy the Tribolube.

Thanks again for spending the time to respond to my questions, even though they aren't critical or serious questions. I am just interested, that's all,
markm

 

[Couv]

I am assuming that you are exclusively using Tribolube now...? Are you on a 13 year run with Tribolube?

Actually I have gone back to using Dow Corning 111 (or it's current name Molykote) for my personal regulators that see 40% O2 or less . Silicone grease IMHO last longer, is more tenacious, is more hydrophobic, and has less tendency to separate than any of the PTFE greases I have used. (Christo-lube 111, Tribolube 71, Braycote, Krytox) Silicone grease is much more economical too.

There is no doubt that a PTFE grease is a superior lubricant fresh out of the tube and freshly applied. But after a year or so all of the teflon based greases separate at least a little bit. I do have a MK2 and one MK10 I have O2 cleaned and lubricated with PTFE grease, but for workhorse regulators I stick with silicone.

Anyway, to address your question of Christo-lube vs. Tribolube 71 I have found Tribolube to separate less than Christo-lube.

BTW I like to yank Dr. Singler's chain every now and then, hence the comment.

 

[rsingler]

It's tough, going against the grain. Christolube MCG-111 is the 800lb gorilla, and Tribolube has had a tough sell.
That said, Christolube absolutely dries in place. It is a real beast to clean, and most of us just leave the residual layer of PTFE in place and lube over it. I don't see that as a problem.
In contrast, T71 just doesn't seem to dry. While Tribolube 66 is favored by many DIY'ers because it's even cheaper than T71, Tribolube 66 does seem to separate out the oil carrier from the PTFE. It's certainly true in the 1lb tubs that I buy. But then, so does Christolube. Additionally, T66 doesn't have quite the temp spread that T71 has, so I don't use it to pack Atomic sealed pistons despite the added cost. I don't think it's quite as responsive (sl. more viscous).

I'll be quite honest: I like T71 for how it feels in my fingertips compared with MCG-111 as I lube orings. It's a subtle thing, but it's real. Between that, the price and its non-drying characteristics, I don't EVER use Christolube unless the manufacturer won't allow a substitute. Add in its suitability for oxygen service at high pressure and it's a slam dunk.
It's maybe $400/lb for T71 and $325 for T66, vs $400/lb for Christolube. Obviously, smaller quantities get huge markups.

Then there's silicone. It's a GREAT non-drying lube! But it is not compatible with oxygen service. For me, the deal breaker is that, plus the fact that you can not clean it off a reg. You can wipe it, but there's no reliable solvent. You can use detergent, but it doesn't emulsify. In other words, if you want to convert that old Mk5 to a deco reg for your 20ft bottle, you can do it yourself. I won't take the risk. Yeah, after a dozen cleanings and droplet or shaken test tube tests it might pass. But at that point you've expended enough labor that you might as well have bought a new O2-clean first stage. But for non-O2 uses, it's perfect. My JJ-CCR specifies it!
I just can't do anything with it near my other tools for reg service.

Bottom line for me? I'm not cheap enough to use T66 to save 30%. I'm not happy with how it separates from the carrier oil (just like Christolube). I pretty much use T71 for everything except my breather and port plug/hose orings. It doesn't dry, which is critical for the threads where salt water infiltrates under pressure (yoke and DIN bolts). Now we can argue about using lube on threads that are "supposed" to be dry-threaded, lol!

If folks would like an alternative source for 10cc of T71 in a syringe with a blunt plastic needle, PM me. Between my Trident account and $4.50 USPS postage, I can probably save you a few bucks. Not too many of you, though. It's a PITA to package.

Finally, an anecdote. Years ago, when I was working with Rudy Mola of Diving Technologies Int'l, Tribolube had just come out, and he was asked to help evaluate it. We did this test together, which is not very scientific, but I've never forgotten it. We took a pencil eraser sized dollop each of T71 and Christolube. We put both in the blue flame zone of a propane torch and just let them sit. Maybe 60-120sec. At the end of the test, the T71 was just gray ash on the end of the spatula. It didn't smoke. It just sat there. The Christolube didn't smoke either, after all that time. But in the middle of the spatula sat a tiny red ember. I've never forgotten it. Does that mean anything? Dunno.

 

[OTF]

^ That's the kind of information dump that makes this website great.

 

[rjack321]

Then there's silicone. It's a GREAT non-drying lube! But it is not compatible with oxygen service. For me, the deal breaker is that, plus the fact that you can not clean it off a reg. You can wipe it, but there's no reliable solvent. You can use detergent, but it doesn't emulsify. In other words, if you want to convert that old Mk5 to a deco reg for your 20ft bottle, you can do it yourself. I won't take the risk. Yeah, after a dozen cleanings and droplet or shaken test tube tests it might pass. But at that point you've expended enough labor that you might as well have bought a new O2-clean first stage. But for non-O2 uses, it's perfect. My JJ-CCR specifies it!
I just can't do anything with it near my other tools for reg service.

Silicon greases (including molycoat and dow corning) will dissolve in xylene or toluene. You can buy them by the quart at most paint supply houses and sometimes the big box stores.

Avoid these vapors by working outside - but it will come off and then you can wash the parts.

 

[rsingler]

Silicon greases (including molycoat and dow corning) will dissolve in xylene or toluene.

I will try that. That is such a common solvent that I'm amazed I was taught otherwise. Thank you - assuming that it truly dissolves it. I was taught that only carbon tetrachloride would work. I'll report back!

 

[rjack321]

I will try that. That is such a common solvent that I'm amazed I was taught otherwise. Thank you - assuming that it truly dissolves it. I was taught that only carbon tetrachloride would work. I'll report back!

They might leave a bit of a residue themselves. So will definitely still need a good simple green hot ultrasonic afterwards. I have used toluene to remove goopy old dow corning from tank neck threads before O2 cleaning. It worked pretty well for that but I have not tried regulator parts.

 

[happy-diver]

Perfect for regulator parts

Yeah toluene works similarly to xylene, they slightly thin and get between the silicone and the material you are cleaning. Okay so it lubricates the silicone as it thins the stuff so the silicone slides off leaving no visible residue
I use a brush and mechanically brush it off takes a few seconds to work then throw it in some detergentised hot
water, do some more parts before plopping it all in the the ultrasonic, no other dechemicalising or prep required

But most definitely I do toluene over xylene due to less residual odour, I think a cleaner surface and I like it better

Xylene reminds me of turps yuck!


Hey methyl ethyl ketone and isopropyl alcohol works but that stuff really kills you even out in the open
Look at some plumbers and drunks


and I'm talking harcore 111 not any of that wet or gloopy diveshop stuff

Bauer also has an interesting sticky silicone

 

[happy-diver]

If those PU o-rings were new, the correct hardness, and well lubricated that is just the opposite of what I would have expected. PU o-rings are known for their resistance to extrusion and good friction/stiction characteristics.

I don't purchase PU because I buy in bulk and the shelf life of PU is short when compared to Viton or EPDM. They also turn brittle sitting in a regulator that goes unused for an extended period.

I'm not a big lubricator and suddenly went on a pu tangent for a day
then new seats and lubed heaps went diving and again screeching
and the next day back in went the epdm

Yeah I've bought a couple of Scubapro Mk10s with both piston orings pu and in pieces

Thanks couv