Scuba Pro Mark 20

[vladimir]

From Undercurrent:
Cracked Regulators: The National Oceanic and Atmospheric Administration had a first stage Scubapro regulator split in half and ordered all their Scuba Pro Mark 20 models out of the water.). Six weeks after reporting the incident to Scubapro they finally got an explanation "the yoke nut had been tightened too hard - overtorqued" during routine maintenance. NOAA accepted the explanation. The Mark-20 yoke nut can be replaced by a sheathed yoke that inhibits overtorqueing, the standard part for the Mark-25. The MK-20 was replaced by the Mark 25 in 2002.

Have a look at the crack at www.ndc.noaa.gov/pdfs/sb05-01.pdf .

 

[SDAnderson]

This isn't "new" news, but important nonetheless - thanks for the reminder. The link you posted didn't work, so I fixed it for you.

 

[redacted]

From Undercurrent:
The Mark-20 yoke nut can be replaced by a sheathed yoke that inhibits overtorqueing, the standard part for the Mark-25. The MK-20 was replaced by the Mark 25 in 2002.

Well, that part is news to me. But my Mk20 and Mk25 (brass) schematics show a common yoke nut, part # 10103115. Can you provide any part numbers for this sheathed yoke?

I'm more curious than interested in changing. If you use a torque wrench and a little common sense, it's pretty easy not to overtorque things like this.

 

[vladimir]

From Undercurrent, the sequel to the story I pasted to start this thread:

Scubapro Mark 20. In our last email we reported that the first stage of a Scubapro Mark 20 regulator used by a diver with the National Oceanographic Atmospheric Administration developed a serious open crack. Scubapro told NOAA that the problem was due to overtorqueing the yoke nut and we reported that NOAA accepted that explanation. We were wrong and NOAA disagrees with Scubapro. NOAA contacted us and Dave Dinsmore, director of the NOAA diving program, said, "Both Scubapro and NOAA hired independent experts to evaluate the cracks and assess the likely cause. NOAA's expert determined that no deformation, thread damage or gouging was noticed at the yoke thread (male) and yoke adapter (female) indicating that the yoke had not been overtorqued." NOAA discovered cracks in three out of 298 regulators. NOAA ordered the MK20 out of the water and Scubapro has since replaced all of NOAA's MK20 regulators with MK25 models. If you own a MK 20, carefully examine the second stage for cracks and if you find one, contact your Scubapro dealer.

 

[Diesel298]

hum.... ill have to look at them more carefully...
i have a din but......none the less.... ill be takin a look

 

[scubamoo]

I work in a public safety dive unit that has approximately 30 ScubaPro MK20's in service (all DIN's). Last week we had a catastrophic failure of one of our 1st stages. It cracked wide open -- just like the pictures on the Univ. Hawaii link below. We are replacing all our MK20's with MK25's.

As of March 17, 2005, NOAA suspended all diving with MK20's and the University of Hawaii did so on March 4, 2005.

Our diver had the failure occur when he opened the tank valve, though a Univ. of Hawaii diver had the failure upon surfacing from a dive...

University of Hawaii Safety Advisory

NOAA Diving Safety Bulletin

 

[jjs]

Well, that part is news to me. But my Mk20 and Mk25 (brass) schematics show a common yoke nut, part # 10103115. Can you provide any part numbers for this sheathed yoke?

Found this.. it contains the part number you were curious about.. I just hope that they are correct and that no other SB regs develop similar issues...

Dear Authorized SCUBAPRO UWATEC Dealer,
Please note the attached correspondence. The first letter is communication to you,
our dealer and the second is information we will be giving out to consumers as
they call in regarding the MK 20 First Stage Regulator.
© 2005 by Johnson Outdoors Inc.

MK20 Yoke / DIN Service Bulletin


--------------------------------------------------------------------------------

Dear Authorized SCUBAPRO UWATEC Dealer,

This is a communication to you, our dealers, to inform you we are in the preliminary stages of an upgrade program for the MK20 first stage regulators.

Recently, we were notified that a diver had reported a crack in and around the body of a MK20 first stage regulator where the yoke retainer seats against the internal body of the regulator. We immediately conducted an internal review utilizing our SCUBAPRO ® Engineering Team. Simultaneously, we asked the independent experts at Exponent Failure Analysis Associates to determine the root cause. Exponent is a leading failure analysis consultancy with technical expertise spanning a wide range of scientific and engineering disciplines.

Exponent has completed an extensive and comprehensive independent review and analysis of the MK20 design and materials, as well as detailed inspection and analysis of both the failed unit and properly working MK20s. They determined the crack occurred due to a combination over torque and exposure to an underwater environment. The crack may be initiated if exposed to over torquing and over time, a larger crack may develop when exposed to harsh environmental conditions and, in a small number of cases cause a failure.

As a result of these findings, SCUBAPRO’s engineering staff and Exponent both recommend that all MK20s be updated with Universal Yoke Retainer (PN 10.103.115). This retainer transfers the mechanical load to the yoke retainer and not the body. The upgrade to this Universal Yoke Retainer and proper torque settings have been found to eliminate the stress placed on the body of the regulator at the location of observed cracking. This update, available in both Yoke and DIN, will soon be available to you to so that you may update your customer’s MK20 first stages. We will be mailing each Authorized Dealer more correspondence on this program within the next week.

In closing, we work hard to earn the trust of you and your customers every day, and know that our reputation is based on what we do, not what we say we will do. That is why when we first learned of a problem, even though it involved a product no longer produced or sold, we took responsibility and immediate action. At SCUBAPRO diver safety comes first.

Please feel free to contact your Sales Representative or our Technical Services Department if you have any further questions.

SCUBAPRO UWATEC
North America

© 2005 by Johnson Outdoors Inc.

SCUBAPRO MK20 First Stage Communication


--------------------------------------------------------------------------------

Thank you for contacting us regarding the SCUBAPRO MK20 First Stage Regulator. We certainly appreciate the opportunity to provide additional information and clarification on this matter.

Since 1996, tens of thousands of MK20 first stage regulators have been used by divers under rigorous conditions in both warm and cold water. When we first learned that a diver had reported a crack in and around the yoke thread area of a MK20, we immediately conducted an internal review utilizing our SCUBAPRO® Engineering Team. Simultaneously we asked the independent experts at Exponent Failure Analysis Associates to determine the root cause. Exponent is a leading failure analysis consultancy with technical expertise spanning a wide range of scientific and engineering disciplines.

Exponent has completed an extensive and comprehensive independent review and analysis of the MK20 design and materials, as well as detailed inspection and analysis of both the failed unit and properly working MK20s. They determined the crack occurred due to a combination over torque and exposure to an underwater environment. The crack may be initiated if exposed to over torquing and over time, a larger crack may develop when exposed to harsh environmental conditions and, in a small number of cases cause a failure.

As a result of these findings, SCUBAPRO recommends that all MK20s be updated with Universal Yoke Retainer (part number 10.103.115). This retainer transfers the mechanical load to the yoke retainer and not the body. This Universal Yoke Retainer and proper torque settings have been found to eliminate the stress placed on the body of the regulator at the location of observed cracking. This retainer will soon be available, free of charge, at an Authorized SCUBAPRO Dealer. A Dealer can be located via our website www.scubapro.com or by calling 619-402-1023.

In closing, we work hard to earn the trust of our customers every day, and know that our reputation is based on what we do, not what we say we will do. That is why when we first learned of a problem, even though it involved a product no longer produced or sold, we took responsibility and immediate action. At SCUBAPRO diver safety comes first.

Please feel free to contact your local Authorized SCUBAPRO UWATEC Dealer or SCUBAPRO UWATEC if you have any further questions.

SCUBAPRO UWATEC
North America

 

[redacted]

www.scubapro.com[/url] or by calling 619-402-1023.

In closing, we work hard to earn the trust of our customers every day, and know that our reputation is based on what we do, not what we say we will do. That is why when we first learned of a problem, even though it involved a product no longer produced or sold, we took responsibility and immediate action. At SCUBAPRO diver safety comes first.

Please feel free to contact your local Authorized SCUBAPRO UWATEC Dealer or SCUBAPRO UWATEC if you have any further questions.

SCUBAPRO UWATEC
North America

Thanks jjs

But I'm afraid this is generating more questions than answers for me. I went thru all the schematics I have of the Mk20 (and the Mk 10!). What I found was that a 12/97 schematic of the Mk20 shows a yoke retainer (nut) part number of 10-600-104. This must be the nut that Scubapro says is the cause of the problem. The next Mk20 schematic I have is dated 01/00 and shows the yoke nut as # 10-103-115 (the good one). I have to wonder why the "new" yoke nut that cures this catastrophic failure problem apparently was put into service last century but the "voluntary recall" is just being initiated now!!! I suspect that, although they say "At SCUBAPRO diver safety comes first" that it maybe comes first right after profit. And I also suspect that the problem was, in fact, discovered last century (and caused the redesign?) and their statement "when we first learned of a problem, even though it involved a product no longer produced or sold, we took responsibility and immediate action" is just as lot of PR hooey. Also, based on what I can see in the '97 schematic it looks to me like one change is in the design of the area where the nut steps from the threaded area to the full bore area above it. The older schematic seems to show a 45 degree slope in the transition from the smaller diameter to the larger diameter. I didn't take any of my Mk20s apart, but a DIN valve that I took off one of my MK20s has a 90 degree step there rather than the 45.

But my next concern is my Mk10s. Here my 12/97 schematic (Mk10 not in production by then) show a yoke nut with that 45 degree slope where the diameters transition with a part number of 10-400-104. But a newer Mk10 schematic dated 02/01 (no production in that time, just a configuration/schematic update) shows a yoke nut part number of 10-103-115. So does Scubapro know that the same potential problem exists with the Mk10s but is just keeping their fingers crossed that it will not materialize as a catastrophic incident?

I like the Scubapro products, the older ones anyway, but I trust the company about as much as a school of sharks on a feeding frenzy.

I'm really hoping DA or one of the other experienced techs can chime in here and embarrass me by explaining how wrong I am and what is really going on.

 

[DA Aquamaster]

But my next concern is my Mk10s. Here my 12/97 schematic (Mk10 not in production by then) show a yoke nut with that 45 degree slope where the diameters transition with a part number of 10-400-104. But a newer Mk10 schematic dated 02/01 (no production in that time, just a configuration/schematic update) shows a yoke nut part number of 10-103-115. So does Scubapro know that the same potential problem exists with the Mk10s but is just keeping their fingers crossed that it will not materialize as a catastrophic incident?

I like the Scubapro products, the older ones anyway, but I trust the company about as much as a school of sharks on a feeding frenzy.

Scubapro has an evolutionary design philosophy that is promoted as being beneficial to customers as they will be able to update their regulators with newer components as they become available on newer but still similar designs. The 109/156 - Adjustable/Balanced Adjustable second stages are a prime example as even the oldest 109 Adjustable can be updated with the current s-wing poppet and a balance chamber to current G250 performance levels.

But from Scubapro's perspective this approach also enables them to continue parts support for older regs while maintaining a much smaller stock of parts. For example the G250 annual service kit works on the Balanced Adjustable, G200B, G250, G500, G550 and S600 second stages (and works on the Adjustable as well if you spend a buck on a new spring and install the G250 annual service kit as you then have a Balanced Adjustable). Similarly the R190 kit will work on essentially all of SP's non adjustable standard downstream second stage designs. So a handful of first and second stage kits service everything and this is a real money saver .

The point being that the use of the current 10-103-115 yoke retainer in the Mk 10 I think just reflects SP's efforts to standardize one retainer for as many designs as possible. This reduces the number of parts that need to be made, stocked and distributed. It also makes DIN kits easier to supply as you need one for the Mk10 through Mk 25, one for the Mk 2, Mk3, Mk 200, Mk 2 Plus and, an oddity in the bunch, one for the Mk 5.

With regard to cracking, the Mk 10 has been in production and used hard since the early 80's and has also been widely copied and manufactured under license. So I suspect that if it were prone to cracking, it would have already been a problem a long time ago.

 

[redacted]

Scubapro has an evolutionary design philosophy that is promoted as being beneficial to customers as they will be able to update their regulators with newer components as they become available on newer but still similar designs.

With regard to cracking, the Mk 10 has been in production and used hard since the early 80's and has also been widely copied and manufactured under license. So I suspect that if it were prone to cracking, it would have already been a problem a long time ago.

Yes, I am fairly familiar with their evolutionary design philosophy. Most of my SP regs are older than my C-cards. And your explanation is quite reasonable for the 21st century change in the Mk10 yoke. But I would be more comfortable with a little information on the nature of the design defect of the yoke nut that Scubapro believes is contributing to this failure of the body associated with overtorquing.

Actually, I was much happier with the idea that it was entirely a problem attributable to overtorquing. I find it a bit scary how many techs and shops may be doing service without using a torque wrench. Apparently, Scubapro may require the shop to have a compressor but has no requirement for a torque wrench.