Scubapro Regulator MK-20 Problem?

[outback]

This came from another board - see http://www.chumclub.org/forums/showthread.php?t=150 for a picture.

I though it scary enough that I should post it here. No idea if it is legitimate or not - I checked on the NOAA site, but they may not have updated it yet. http://www.ndc.noaa.gov/rp_bulletins.html


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. If you have a MK20 regulator and have an urgent need to dive, please contact Lisa Glover at the NOAA Dive Center to arrange for a replacement regulator. She can be reached at Lisa.Glover@noaa.gov or 206-526-6446.

We understand that this may pose significant hardship on a number of our divers, but feel that the potential risk involved with continued use of these regulators necessitates this action.

 

[DA Aquamaster]

This one hash been hashed to death at the deco stop.

Basically, nearly all the techs involved in the discussion feel that it looks like a clear case of someone over torquing the yoke nuts on them. The non tech inclined have various other Ralph Nader type conspiracy theories and now live in fear of their Mk 20's cracking and failing at depth.

The debate mostly centered on the quality and questionable parentage of the NOAA tech(s) who worked on the affected Mk 20's with supporting evidence in the form of a complete abscence of the problem among the rest of the diving world.

This is the first I have heard of the Mk 25 replacement issue, but it sounds like a typical knee jerk government response conveying the appearance of taking decisive action but in actual fact having no real substance or usefulness and no real effect other than wasting tax dollars. There is in fact zero difference in that particular area of the reg between the Mk 20 and Mk 25, so swapping the all their Mk 20's for Mk 25's is not going to solve the problem of a tech not knowing how to use a torque wrench.

There has bene no mention of problems amoung Sp or SP techs. I own several Mk 20's two of which see 150 plus dives per year with drastic changes in temperature from 90 plus degrees on the boat to upper 30's at depth in under 2 minutes. I also servvice numerous other Mk 20's annually and I have not seen the problem. My conclusion is that if you don't massively overt orque the yoke nut every year when you service the reg, it won't crack.

So with this nifty synopsis maybe we can keep this thread short and not regurgitate everything all over again here.

 

[divenut2001]

This one hash been hashed to death at the deco stop.

Basically, nearly all the techs involved in the discussion feel that it looks like a clear case of someone over torquing the yoke nuts on them. The non tech inclined have various other Ralph Nader type conspiracy theories and now live in fear of their Mk 20's cracking and failing at depth.

The debate mostly centered on the quality and questionable parentage of the NOAA tech(s) who worked on the affected Mk 20's with supporting evidence in the form of a complete abscence of the problem among the rest of the diving world.

This is the first I have heard of the Mk 25 replacement issue, but it sounds like a typical knee jerk government response conveying the appearance of taking decisive action but in actual fact having no real substance or usefulness and no real effect other than wasting tax dollars. There is in fact zero difference in that particular area of the reg between the Mk 20 and Mk 25, so swapping the all their Mk 20's for Mk 25's is not going to solve the problem of a tech not knowing how to use a torque wrench.

There has bene no mention of problems amoung Sp or SP techs. I own several Mk 20's two of which see 150 plus dives per year with drastic changes in temperature from 90 plus degrees on the boat to upper 30's at depth in under 2 minutes. I also servvice numerous other Mk 20's annually and I have not seen the problem. My conclusion is that if you don't massively overt orque the yoke nut every year when you service the reg, it won't crack.

So with this nifty synopsis maybe we can keep this thread short and not regurgitate everything all over again here.

Saw this yesterday on another forum on SB. Since I own one I was very concerned and immediately called my LDS. The Scubapro tech had not seen or heard of any problems with the MK 20 and is going to contact Scubapro on Monday morning for more info. I will also relay the info from this thread to the tech hopefully before he calls Scubapro. I will post what Scubapro's comments are as soon as I know. Thanks again Aquamaster.

 

[DA Aquamaster]

The discussion at the deco stop started last August with someone "just getting this the other day" and I thought I remembered an even older discussion on it elsewhere where some other well meaning individual also "just received" the warning and passed it on. It appeared to me that there was a definite pattern there and the addition of the new Mk 25 twist to the new version of the story was suspicious. So I thought I would do a bit more research today to try to determine the source of this recurring "just received important safety warning" theme regarding Mk 20 cracks.

After searching several sites including the NOAA and SP websites, I am virtually certain that it is a sort of urban ledgend very loosely based on fact that just keeps resurfacing periodically.

The ledgend is I think based on the following information:

There has never been anything related to cracks being found in Mk 20's on the SP "Dealer Only" website where safety and engineering notices are posted. But Engineering Bulletin #255 was issued in May of 1997 and lowered the acceptable torque range for the yoke nuts and DIN retainers slighty from 325-375 in lbs to 275-325 in lbs. It discussed a re-evaluation of the torque specifications for the yoke nuts and DIN retainers used on the Mk 9, Mk 10, Mk 15 and Mk 20 regulators (The Mk 25 was not yet developed at that point and the Mk 5 was probably regarded as being too old for anyone to care - although I actually serviced three Mk 5's today, more than any other single model of reg I saw today).

The purpose of this bulletin was clearly to reduce the instances of yoke nuts becoming stuck due to the effects of excessive torque combined with long term corrosion. Along with the lower torque range, Engineering Bulletin 255 also stated that "in addition a small amount of silicone lubricant or Christolube (as applicable) should be applied to the threads to reduce long term corrosion and make removal of the components easier at the next servcie interval."

Clearly the intent of the bulletin was not to avoid cracks in Mk 20's but rather to reduce problems with stuck yoke nuts in all first stages using this type of yoke nut design. This is consistent with the emphasis placed on the problem at tech seminars. SP has for quite a while been concerned with some techs guestimating the torque on yoke nuts which usually results in them being over torqued which in turn can lead to them being very hard to remove at the next annual serivce when the effects of corrosion or salt deposits are added. It is not a safety issue as much as it is a monetary issue for SP as they end up having to replace damaged yoke nuts and 1rst stage bodies under warranty if the tech screws them up trying to separate them.

Now, this is where the urban ledgend gets started:

Attached to the bottom of the bulletin (and only indirectly part of it) was a stock warning box with a little "pay attention stupid" sign ("!") in it stressing the need for techs to follow torgue specifications. This warning stated "Over torquing could, over time, result in structural damage to the regulator 1rst stage body. A catostophic failure of a regulator 1rst stage could result in serious personal injury or death. Regulators should always be pressurized slowly to avoid undue stress." Surprise, surprise, this wording sounds amazingly similar to the wording I keep hearing about in the alledged NOAA warning.

So Engineering Bulletin 255 and Scubapro's on going tech training program are the factual basis for the techs opinions on other boards that the alledged NOAA Mk 20 cracks were due to a shop monkey overtorquing them. And at the same time, given the similarity in wording, I suspect that Engineering Bulletin #255 is itself the source of the ledgend indicating that NOAA issued a safety warning after discovering several Mk 20's with cracks in them. I can't find the NOAA warning, so at this point I doubt it even exists. If someone can find a copy and/or any info on any subsequent investigation or findings, I'd love to see them.

I do however have no doubt that you could crack a Mk 20 first stage body in the yoke nut area by massively over torquing the yoke nut or DIN retainer, and SP clearly states this could occur. But instances of this occurring would be cases of severe reg abuse by a lazy and moronic tech and would not be the result of an engineering defect or problem with the metalurgy.

So in short, if you own a Mk 20, don't worry about it cracking. If you just happen to enjoying worrying and are going to do it anyway, consider quizzing your tech about torque specs and asking to actually see his torque wrench to prove he owns one before you hand over your reg (any reg, not just the Mk 20) for it's next annual service.

 

[redacted]

So in short, if you own a Mk 20, don't worry about it cracking. If you just happen to enjoying worrying and are going to do it anyway, consider quizzing your tech about torque specs and asking to actually see his torque wrench to prove he owns one before you hand over your reg (any reg, not just the Mk 20) for it's next annual service.

Come on now DA, ideas like that are liable to put a lot of shop monkeys out of business! What are you going to look for next? Flowbenches and Ultrasonic cleaners!!!!

My impression is that SP torque spec on a yolk nut is quite a bit higher than other mfgrs. If under 20 ft/lb works on most other regs, and the 0-ring is making the seal, why does SP take it higher?

 

[DA Aquamaster]

I think part of the issue is the general shape of the MK 10/15/20/25 first stages. The long part of the reg makes what amounts to a handle. So if the reg is pressurized, the yoke nut/DIN fitting will not move as air pressure will be holding it tight to the valve, but if a clueless diver pulls on long end of the reg hard enough in the lefty loosey direction, he/she can actually loosen the yoke nut/DIN fitting if the torque value is much lower. I have seen this happen a time or two on the aluminum Ultralight Mk 20's with their lower torque specs (240-250 in lbs).

With most other first stage designs, this is less likely to happen as the reg is not "long" enough to provide much leverage. It would be pretty hard to put much torque on a Conshelf, Titan, or Mk 2 Plus looking first stage by hand.