Reminder about unavoidable OOAs

[Diver0001]

Has anyone here tried to dump 850 psi by holding the purge button down for 10 seconds.

Around here the K valves we have will dump about 1000 litres a min if they're wide open. That's a little over 2 min for a full 10 litre tank. I'll spare you the math but even without a reg attached an AL80 with the K valves I'm used to seeing will dump absolute maximum of 200psi in 10 seconds.

Curt Bowen did some interesting tests with freeflows in real word conditions. They're posted on the decostop .

R..

 

[Web Monkey]

Even at 30 CFM, which won't get delivered through a second stage, 10 seconds vents 5 cf. At a full 30 CFM, 22.6 cf would take 45 seconds.

I would suspect the guy who had the freeflow wasn't actually timing it.

I was simply mentioning that seemingly huge flow rates aren't as bizzare as they sound.

Terry

 

[geraldp]

.
.
Normal response to a freeflowing second stage at the surface is to turn it face down. Second response is to whack it on your hand. Third response is to turn down the adjustment if it has one (at least some of the atomics do).

And 850 PSI in less than ten seconds? I don't think so.

Tried the first response - no help. Tried the second response - no help. Unfortunately the SS1 doesn't have an external adjustment. Then for some reason I crammed it in my mouth to see if I could stop it that way, but the excess air just blew out the exhaust valve. About that time it stopped flowing, as there was NO air left. That's when I had other things on my mind, as my BC was empty (and wouldn't hold air by manual inflation) and I was negatively bouyant. So Web Monkey is correct in that I wasn't precisely timing it, but it wasn't very long. My first stage is an Atomic Aquatics M1.

When I got on the boat and connected it up to a new tank it was still stuck open. I tapped it on the gunnel and the inflator valve and spring popped off. So maybe it got some sand stuck in it, and maybe it wasn't put back together properly. I'll find out I guess when I get back to the shop with it.

 

[Dan Gibson]

Most likely the case.

Someone mentioned shear failure. A trained engineer can spot whether or not this is a tensile or shear failure. It's been many years since I had a materials class, but I would think a shear failure would probably support over torquing.

I can't remember, but IIRC putting a member under torsion can result in either a shear or tensile failure. Putting it in tension only results in tensile failures. Correct me if I'm wrong, I'm not up to speed on Mohr's diagrams anymore.

IF you had just had the reg serviced the fault may lie with the installer overtorquing the bolt.

FT

 

[divenut2001]

That's why I love this board, so much valuable information to be shared. I have the same reg and the thought of it failing never entered my mind.

And thank you Uncle Pug, you are truley a wise man. I am getting ready to make the switch from a jacket BC to a BP/W and now it looks like I'll be making a reg change too....

 

[wedivebc]

Just wondering Xman, were you using nitrox when this happened? If so what mix?

 

[MSilvia]

This was posted on another board. FYI FWIW:

This is an important Diver Alert issued by the NOAA Dive Center, Seattle, WA.

There is a potential problem with MK-20 first stage regulators manufactured by
SCUBAPRO.

Cracks have been found in three MK-20 first stage regulators that were issued to NOAA divers. These cracks seem to happen over time and do not appear to be a sudden event. One of the cracks was found by a diver during diving operations prior to his dive and the other two were discovered during annual service here at the Dive Center. These cracks are similar nature and are located in the body of the 1st stage regulator where the scuba yoke assembly attaches to the 1st stage. (reference pictures below). The crack is on the high pressure side of the regulator and may result in a catastrophic failure of the regulator.

To check for this potential crack, remove the decorative plastic cap at the base of the first stage. This can be done, in most cases without tools by twisting and pulling on the cap. This inspection is to be done at the beginning of each diving day.

If, after inspection, you suspect a crack in your SCUBAPRO MK-20 first stage,

DO NOT DIVE THE REGULATOR!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This is an important Diver Alert issued by the NOAA Dive Center, Seattle, WA.

Effective immediately, all NOAA divers must discontinue diving with the Scubapro MK-20 first stage regulators. Another catastrophic failure (reference photo
below) of a MK-20 was recently reported to the NOAA Diving Center, that could have produced serious injury.

We are currently working with Scubapro to replace all MK-20 regulators with MK-25 regulators as soon as possible. In the interim, the NDC has a limited
number of MK-25 regulators available for immediate issue on a case-by-case basis.

 

[divenut2001]

This was posted on another board. FYI FWIW:

This is an important Diver Alert issued by the NOAA Dive Center, Seattle, WA.

There is a potential problem with MK-20 first stage regulators manufactured by
SCUBAPRO.

Cracks have been found in three MK-20 first stage regulators that were issued to NOAA divers. These cracks seem to happen over time and do not appear to be a sudden event. One of the cracks was found by a diver during diving operations prior to his dive and the other two were discovered during annual service here at the Dive Center. These cracks are similar nature and are located in the body of the 1st stage regulator where the scuba yoke assembly attaches to the 1st stage. (reference pictures below). The crack is on the high pressure side of the regulator and may result in a catastrophic failure of the regulator.

To check for this potential crack, remove the decorative plastic cap at the base of the first stage. This can be done, in most cases without tools by twisting and pulling on the cap. This inspection is to be done at the beginning of each diving day.

If, after inspection, you suspect a crack in your SCUBAPRO MK-20 first stage,

DO NOT DIVE THE REGULATOR!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This is an important Diver Alert issued by the NOAA Dive Center, Seattle, WA.

Effective immediately, all NOAA divers must discontinue diving with the Scubapro MK-20 first stage regulators. Another catastrophic failure (reference photo
below) of a MK-20 was recently reported to the NOAA Diving Center, that could have produced serious injury.

We are currently working with Scubapro to replace all MK-20 regulators with MK-25 regulators as soon as possible. In the interim, the NDC has a limited
number of MK-25 regulators available for immediate issue on a case-by-case basis.

What was the date of this notice?

Has there been a recall of the MK20?

Do you have a link to the original notice?

Thanks!

 

[liberato]

According to Google, the last instance of that memo was from last year.

 

[Xman]

Just wondering Xman, were you using nitrox when this happened? If so what mix?

Not sure what relevance it has, but I was diving air on the previous dive, and there was air in the tank that the reg was attached to when it failed. Thankfully I was not "using" it at the time as it failed during gearing up.

As for the memo mentioned above. Thanks for posting it. I had not heard about that, but it is an entirely seperate issue. My Mk20 certainly has not displayed any signs of a crack where the yolk assembly attaches. Where mine failed seems impossible to inspect (until it fails) as it is hollow chromed brass bolt which attaches the LP swivel to the rest of the regulator. As it is a chromed part I would imagine that even if the bolt were carefully examined it may be impossible to determine internal damage due to potential over torqueing.