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]

It's much more damage-proof and robust than the rubber rings in my kit.

Polyurethane.

 

[markmud]

Thank you Akimbo!

Thanks so much!
m

 

[markmud]

Akimbo,

I have used silicone grease (no-petroleum additives type) for lubricating spool O-rings and for LP hose to 2nd stage regulator seal. I have dived Nitrox to 35% with these regulators. I did not have Christo-lube at the time.

Question:
Could the use of SCUBA approved silicone grease (for general scuba use, not O² service) in a regulator used for EANX (< less than 40%) create a combustion or CO problem?

cheers,
markm

 

[Akimbo]

Question:
Could the use of SCUBA approved silicone grease (for general scuba use, not O² service) in a regulator used for EANX (< less than 40%) create a combustion or CO problem?

The Safe Answer:
Oxygen compatible lubricants come and go at the same time that our knowledge is increasing. The prudent answer to follow manufactures and industry recommendations.

The "real" answer, which is pretty complex:
NASA did millions of dollars of theoretical and physical research on O2 fires after the Apollo fire. A great deal of what we know from a chemistry and engineering perspective was derived from and built on that work. One of the many things they discovered was that the rare industrial O2 fires in high pressure piping systems resulted from tiny metal particles that were picked up by gas moving near the sound barrier which caused them to glow red hot. Those glowing particles contacted materials that caused the explosions, which is nothing more than very rapid combustion.

They showed us a NASA produced 16mm high speed film in Navy Saturation training that that captured it. There is no magic here, the basic physics of combustion still apply. Adequate amounts of Oxygen + Fuel + Heat (ignition temperature) = fire/explosion.

Selecting the optimum lubricant is only part of this equation (fuel). You still need a combustion source. Increasing PPO2 lowers the ignition temperature. Proper Oxygen cleaning is just as concerned with eliminating those tiny metal particles that are inherent in machining metals as it is about removing combustible lubricants.

So, can divers get by with standard hardware store food-grade Silicone lubricants? Sure, until an adequate ignition source is introduced. That ignition source can be a tiny partially rusted steel particle in your Scuba tank that gets sucked into the first stage, which can accelerate it to very high velocities. Opening your valve slowly and using air is lower risk than opening the valve fast on 40% EAN. The risk is even higher on pure O2 at full cylinder pressure.

I'm sure we could dig up the formulas on the Internet but what we can't be sure of is accurately filling in all the variables in these formulas. Back to the simple answer to a complex question: Use lubricants approved for the application because they have higher ignition temperatures and a long history that has proven to be safe in the application.

Oh, and you don't have to worry about CO because the explosion would kill you first.

 

[markmud]

The Safe Answer:
Oxygen compatible lubricants come and go at the same time that our knowledge is increasing. The prudent answer to follow manufactures and industry recommendations.

The "real" answer, which is pretty complex:
NASA did millions of dollars of theoretical and physical research on O2 fires after the Apollo fire. A great deal of what we know from a chemistry and engineering perspective was derived from and built on that work. One of the many things they discovered was that the rare industrial O2 fires in high pressure piping systems resulted from tiny metal particles that were picked up by gas moving near the sound barrier which caused them to glow red hot. Those glowing particles contacted materials that caused the explosions, which is nothing more than very rapid combustion.

They showed us a NASA produced 16mm high speed film in Navy Saturation training that that captured it. There is no magic here, the basic physics of combustion still apply. Adequate amounts of Oxygen + Fuel + Heat (ignition temperature) = fire/explosion.

Selecting the optimum lubricant is only part of this equation. You still need a combustion source. Increasing PPO2 lowers the ignition temperature. Proper Oxygen cleaning is just as concerned with eliminating those tiny metal particles that are inherent in machining metals as it is about removing combustible lubricants.

So, can divers get by with standard hardware store food-grade Silicone lubricants? Sure, until an adequate ignition source is introduced. That ignition source can be a tiny partially rusted steel particle in your Scuba tank that gets sucked into the first stage, which can accelerate it to very high velocities. Opening your valve slowly and using air is lower risk than opening the valve fast on 40% EAN. The risk is even higher on pure O2 at full cylinder pressure.

I'm sure we could dig up the formulas on the Internet but what we can't be sure of is accurately filling in all the variables in these formulas. Back to the simple answer to a complex question: Use lubricants approved for the application because they have higher ignition temperatures and a long history that has proven to be safe in the application.

Oh, and you don't have to worry about CO because the explosion would kill you first.

Thanks for the in-depth response Akimbo,

So, bottom line, the flash point for SCUBA approved silicone grease is lower than for Christo Lube. We should be safe and religiously use the lubricant with the highest flash point.

thanks again,
m

 

[happy-diver]

Polyurethane.

I replaced six Scubapro Mk10 small piston orings with these one day and they all screeched like heck

What happened, O Venerable couv

 

[markmud]

@Akimbo and @rsingler,

What are your preferences:

Tribolube 71 or Christo Lube MCG 111 (Dynamic Lube)?

Do you use Christo Lube MCG 129 (General Lube) for some applications?

I have read that Tribolube does not leave near the residue build-up that Christo Lube MCG 111 does. Is that a sales pitch or true (IYHO)?

I am asking because my small vile of Christo Lube is almost empty. It only had about 10 drops in it when I got it. I am preparing to buy a 2 ounce size tube (or syringe?) and wish to spend $30+ on the better product.

I should be getting my Regulator Savvy Book and a few specialty tools soon. I have a permanently retired 1st stage and 2nd stage that I will disassemble and reassemble for fun. Edit: UPS notified me that my Reg Savvy Book will be here on Wednesday.

Don't worry, I won't be going into business. Just having fun.

cheers,
m

 

[Akimbo]

Do you use Christo Lube MCG 129 (General Lube) for some applications?

I have used Dow Corning 111 for decades for everything including breathing systems for air or lower O2... usually much lower.

For Air Service Only:
Dow Corning Molykote 111 (previously Dow Corning Silicone 111)

I really haven't developed a preference for any of these so would go with @rsingler's advice. I used whichever lube was on the bench or in the clean room.

For Nitrox and Oxygen Service:
Engineered Custom Lubricants: ChristoLube MCG 111 and ChristoLube MCG 129
Aerospace Lubricants: Tribolube 71

 

[markmud]

I have used Dow Corning 111 for decades for everything including breathing systems for air or lower O2... usually much lower.

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 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

 

[Couv]

I replaced six Scubapro Mk10 small piston orings with these one day and they all screeched like heck

What happened, O Venerable couv

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.