1: O-rings for Divers
“ I'm a recreational diver. Why should I care about O-rings? ”
“ 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
“ Don’t worry. Catastrophic O-ring failures are extremely rare, as long as you know what you're doing. ”
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
- SPGs (Submersible Pressure Gauges)
- Dive Computers
- 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 TypesO-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:
- 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.
- 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]
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]
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]
Post 5: O-ring History
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]
Special thanks to the Scubaboard Moderators that helped me with this thread and XS Scuba for their technical assistance.
Continued in the next post