Scubapro Plastic Air barrel Cracking

[NJDiver07866]

I'm seeing a good amount of S500-555/600 etc.. with a plastic air barrel that has either a split or some cracking where the metal threads meet the plastic barrel.

I know if you crank on the nut too much it can crack the barrel....so I always am delicate not to over tighten the air barrel nut.

But what are your experiences with this barrel? I always get some good feedback here..

Thanks all

 

[DA Aquamaster]

I service a lot of them and keep a spare on hand, and that says a lot.

Over tightening is not an issue if you keep an o-ring under the nut on the air barrel, but I see a lot of them coming in for service where the o-ring is missing which allows the end of the air barrel to get pulled flush with the case. That again is probably not an issue if all the dimensions are still correct, but unfortunately we are talking about two different types of plastic here that can expand and contract at different rates if subjected to extreme and rapid temperature changes.

Personally I dive with metal Air barrelled G250s and G250Vs exclusively, although in the past I have used (and liked) the metal air barrelled G500.

 

[Zung]

Hello DA, would you care to elaborate on your current preference for the G250, in particular over the 109? Thanks.

NJ, sorry about the hijacking.

 

[DA Aquamaster]

Performance wise there is no noticeable difference between a G250 or G250V and a Balanced Adjustable or for that matter a properly tuned R109 Adjustable when used on a balanced first stage. In fact, the heat transfer is better on the metal R109 and R156 so they are better choices for extremely cold water diving.

Another advantage with the R109 for someone who does their own service is the very generic and flippable seat. I suspect the same thing would work in the G250 if you used R109 internal parts (seat, seat carrier, spring and spring pad) under the G250 adjustment knob.

I suppose my major reason for retiring my Balanced Adjustabels was the misplaced concern of some cave diving buddies regarding my "old" regs. Another reason was commonality of parts and tools for rebuilding in the field. Not having to mess with the clamp on the metal case is nice.

I also converted several G200s and G200Bs to essentially G250 status with new G250V air barrels so it was a fairly cheap upgrade.

 

[Zung]

Thanks for sharing another valuable experience, DA. In my particular case, I've got a couple of 109's that come with special Allen screws that are between 2 and 2.5 mm; it took me over an hour to file down a 2.5 mm Allen wrench to size, and I sure hate to loose it.

Back to topic: the jam nut o-ring's (items #6, 01050347, 2-014) are good Conan-proofers. But I find they remove the feeling (or feedback) I get when the nut starts engaging the stop. I have 1 G250 "Rhapsody" that came with those, and I ended up removing them.

 

[NJDiver07866]

Thank you for your inputs. I appreciate sharing your experience.

The light bulb went off. When I took off the air barrel nut the o-ring under the nut was cut like someone took a exacto knife to it.

I rebuilt the reg and did a negative pressure suck test and heard a hiss of air getting sucked in from around the air barrel. I put some soap on it and sucked in and the soapy water sucked in through the air barrel and case.

I thought it was just some schmegma/crud on the air barrel o-ring.. took it off did not see anything but noticed a linear split on the square plastic that attaches to the metal threads of the air barrel. It was split right where it looks like the plastic was joined together in the mold. It was almost too small to see with the naked eye..

I swapped it out with a spare barrel and the reg locked up with no hiss.

so I'm thinking I have to pay even more attention to this part on future regs.

I can now see why the metal air barrel is more favorable...

I appreciate your help.
Rich

 

[Texfrazer]

Thanks for sharing another valuable experience, DA. In my particular case, I've got a couple of 109's that come with special Allen screws that are between 2 and 2.5 mm; it took me over an hour to file down a 2.5 mm Allen wrench to size, and I sure hate to loose it.

Dang! And I thought I was doing you a big favor by sending those allen screws. I didn't know you were going to have to machine your own driver!

At least you won't have to try and drill out one of your 109 clamps due to a screw letting go on you. I'm going to be attempting my 2nd drill/tap out sometime soon, which is why I sent you the allen screws.

 

[Zung]

Actually, you ARE doing me a favor: I went all over town to find the key, and nobody even have anything close to the SCREWS! I'd have to order them from McMaster and pay a small fortune for shipping otherwise! The hour long job is because I have lousy files, a buck a piece or close to that.
Thanks!

Edit
The size of the allen wrench that fits is 2.45 mm

 

[roy dun]

I just opened up my S555 regulator ans discovered that I have cracks forming on the plastic air barrel. Also discovered that the poppet spring also developed a corrosion crack. Anyone know if these two items can be purchased or just tossed and buy a new regulator.

I think the spring must have had a nick during production and thus the corrosion crack developing into a spring failure. On the other hand, is thermal stress the reason for the air barrel developing hairline cracks?

In any case, SP should have stuck with a metal barrel or a thermoplastic that can take thermal stresses better. . .

 

[Zung]

It has been mentioned elsewhere that SP is reverting back to a metal barrel for the S600 (basically the same thing plus the adjustment). If you're the original owner, try to take it back and ask for the metal barrel under warranty.