Is the SPG O-ring supposed to be replaced during annual inspections?

[Zung]

These o-rings last a long time. My wife's SPG just turned 20 and started burping a few bubbles at a time. I opened it up and couldn't believe the crud and verdigris that were inside, and the o-rings looked like crushed bagels. Obviously, none of the dive shops I was using bothered to clean it. I was thinking of replacing it all together, but, just for the heck of it, cleaned it up, replaced the o-rings with what I had in a save-a-dive bag. To my surprise, it works.

Bottom line: include the SPG in your annual inspection. Oh, and the other hoses too.

 

[halocline]

It is worth noting that the regulator manufactures do not consider the o-rings in the HP hose, or any other hose for that matter to be part of their regulator so they offer no recommendation on the service interval for those parts.

Actually, scubapro includes the funny metric o-ring for the LP hose (2nd stage end) in the 2nd stage kits. It's considered a dynamic o-ring, so it's replaced at annual service. The 003 o-rings in the HP spool are likewise dynamic, so it kind of makes sense to replace them.

Given the pressure differential, a 90 duro o-ring is probably the best choice, but I see 70-75 duro o-rings in those all the time. I'm not sure it makes a great deal of difference, like it does in the HP piston spot.

I would not use a dental pick at all for this spot. Dental picks are very hard steel, and usually very sharp. All it takes is a tiny scratch and it's going to leak. The o-ring picks sold by scubatools are IMO much better.

 

[Firefyter]

Here's a good link from Scubatoys that shows you how to replace those:

Spool O-Ring Replacement

It's a quick and easy job, and I always carry spares since they're so cheap

 

[fppf]

I find a lot of people in the dive industry really don't understand orings very well.
And I have not found anyone that really teaches about them either.

A 75A shore oring is technically going to be to soft for a HP spool. A shore 90A is what you want because of the high pressure and the clearance between the pin and the cylinder. If you take out an oring and find the little hairs hanging off it, that means it was pinched or it started to extrude. You also want a material that is good in dynamic systems with good wear resistance. A small amount of lubricant is also critical in any dynamic seal. Lubercation in phnumatic systems is the hardest thing to maintain and the lack of it is the biggest oring killer.

For those that want to learn more about oring design Parker wrote the book on them.
Its a little deep reading but at the end they talk about failure modes and at the beginning they talk about material selection and other things.

http://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf

 

[HenrikBP]

I replace them annually and lube them judiciously with O2-compatible grease (Tribolube). I get most of my o-rings from Divegearexpress.com; the 75 durometer -003 o-rings are what they sell, so that's what I use. For the people who replace their own, are you using a higher durometer o-ring?

I've only used a few 90 durometer Viton o-rings. Only a handful of dives on them yet, so no real experience. As I believe awap or mattboy mentioned at some point, the 90 duro can be a bit challenging to install, so carry a spare spool with fresh o-rings already installed instead.

Henrik

 

[Bubbletrubble]

Although I haven't had any issues at all with 75A durometer o-rings on the HP spool, I figured that some people would say that 90A durometer is preferable for that application. Seems a little strange that many of the online scuba retailers don't sell 90A durometer o-rings in that size.

@fppf: Frankly, I don't have the time to read the entire Parker handbook on o-ring design.
What material would you recommend for HP spool o-rings? (nitrile, viton, EPDM)
From which online retailer would you recommend buying -003 90A durometer o-rings made of the recommended material?
Hmmm. Looks like McMaster-Carr is selling -003 90A viton o-rings for about $9 per pack of 50. That looks like an option.
EPDM o-rings in 90A durometer seem harder to find online.
I've also ordered o-rings from Aoptec.com. Unfortunately, the company only sells nitrile o-rings of a 90A durometer.
Normally I wouldn't hijack a thread like this, but I think that the OP would be interested in this info, too.

 

[Jim Lapenta]

Scuba tools makes a $5 tool called a HP bullet tool that makes replacing HP spool rings a breeze. Just a delrin block with a pointed piece of rod that has a recess in the other end that fits over the spool. Some lube and the ring slides right on. No pick needed except the one to remove the old one. As to the service issue maybe I was lucky but the shop I was trained at always checks the SPG and if needed cleans the threads on the HP hose and gauge, checks the spool, and replaces the orings if needed. They are cheap and easy to do. Shops that neglect this, and based on regs I've serviced there are a few, are just being chintzy and lazy. I don;t care if it is suggested or not. It takes all of two minutes to check. No different than the ones that do not pull back hose protectors and clean the crud from them. Seen a bunch of those as well. Even though every diver should pull em back when rinsing anyway, many have not been taught to properly care for their gear. Another victim of the shorter condensed OW course.

 

[fppf]

In section 2 of that manual they review the different types of materials out there. It should not take all day to read a chapter of a book

Nitrile has good wear resistance, but it lacks resistance to weather and ozone. In the higher O2 mixes used it would tend to break down faster.

Viton has ok wear resistance, but it is resistant to almost anything you can throw at it. Very low gas permeability means in HP gas it tends not to get "bent" (yes Orings can get bent too!) It also resists burning and oxidation, which is good for O2 usage.

EDPM has similar properties to Viton, but has a little better wear characteristics. It also has low gas permeability and good resistance to ozone and O2.

All and all, I personally use Viton. I know a few people that have switched to EDPM.
I get my standard Orings from Grainger, they have the lowest prices in most cases, but you need an account there. McMaster Carr is good as well, but I find there prices a little higher.

Again, as always these are my opinions and your mileage may vary. Only qualified techs should service stuff and use only OEM parts doing so.

 

[Bubbletrubble]

In section 2 of that manual they review the different types of materials out there. It should not take all day to read a chapter of a book

And that just cost you a "Thanks."

All and all, I personally use Viton. I know a few people that have switched to EDPM.
I get my standard Orings from Grainger, they have the lowest prices in most cases, but you need an account there. McMaster Carr is good as well, but I find there prices a little higher.

I appreciate this info.
In case anyone else is interested in having a quick link, Grainger sells a pack of 100 -003 90A viton o-rings for less than $5.

Only qualified techs should service stuff and use only OEM parts doing so.

Sorry, but I don't anticipate purchasing loose o-rings any time soon from Apeks, Aqualung, Scubapro, Sherwood, etc. I'll happily assume the risk of using non-OEM, high quality generic o-rings.

 

[HenrikBP]

O-Rings, Inc. Since 1958 - Buy Online

O-rings Online Frameset

Precision Associates Inc. | Custom Seals, Rubber Seals & HNBR Seals

are all good places to buy o-rings. Precision Associates has a fairly high o-ring and $$ minimum, but stock some pretty obscure sizes. All provide quick turn-around.

For O-rings USA be very aware of the number of o-rings to order before you get a price cut. It's entirely possible to buy say 79 o-rings for ~$17 when 80 o-rings would have cost you ~$8 (don't ask - I was even warned before hand ...)

Edit; just looked at O-rings USA, and no longer see their discount cut-off - just the lower "straight" cost. Good change.

Henrik