Scubapro Cracking Problem (revisited)

[oceancurrent]

Recently someone I know had a regulator explode while hooked up to a cylinder. Luckily nobody got hurt, but only be sheer luck since the regulator got ejected like a projectile. The diver never named the manufacturer of the reg, but it does look like a ScubaPro based on the photo. A friend of mine did some research and found a few pointers that may be related:
Warning! Scubapro MK 10 fault [Archive] - ScubaBoard
Scubapro MK20 Cracking Problem Deepens: Undercurrent 08/2005

It looks like there have been a few incidents when various ScubaPro regs have cracked in a very similar way. The problem seems to be traceable to cracking of the regulator body at the base of the DIN/Yoke female threads as result of too much tension on the threads from the DIN adapter / Yoke nut. It looks like a very real and legitimate point of concern.

From experience, I know that the DIN adapter needs to be quite snug, otherwise it easily comes loose when the regulator is attached to a cylinder. I tend to tighten it as much as possible with a torque wrench, but I don't seem to get anywhere close to the manufacturer specs. Which is quite surprising to me since I already feel like I have tightened the piece a lot and have always been worried about the effect on the threads.

So, does anyone know anything about this problem with ScubaPro (or other brands)? Do you know if ScubaPro have addressed it and how (particularly for DIN adapters)? Is there a reason to be concerned? How much do you tighten your "DIN adapter" to the regulator body so that it doesn't come loose yet it's not overtightened?

 

[Bubbletrubble]

It's good practice to torque the yoke nut or DIN connector to manufacturer specs.
I always do.

It's critical that the torque wrench is calibrated properly, though, and that the proper math is done to account for any adapters (crowfoot or socket extensions) that are fitted onto the end of the torque wrench.

When was the last time you calibrated your torque wrench?
This could explain why the part seems to be "tight enough" but nowhere near manufacturer specs.

 

[redacted]

It sure looks to be a Scubapro Mk10. Newer schematic (02/01) calls for a torque of 266 inch pounds (22 ft-lb). Older schematic (12/97) calls for 275 to 325 inch pounds (23 to 27 ft-lb), so your torque wrench would have to be pretty far off to exceed that just through calibration. That break has both a new (shiny brass) and an older (tarnished brass) component. I suspect the smooth, old break is from over-torquing the retainer and the rough, new break is where it just gave up. One interesting thing is I believe the Mk10 used the same retainer design as was subjected to a recall on the Mk20.

That could really give you a headache, not to mention taking your breath away.

BTW, assuming the warranty has long expired, I wonder if you can trade that regulator (and all copies of that picture) to Scubapro for two Mk25/A700s.

 

[oceancurrent]

One interesting thing is I believe the Mk10 used the same retainer design as was subjected to a recall on the Mk20.

So, how exactly did they modify the retainer to fix the issue? How can one tell the old retainers from the new ones (I am more interested in the DIN adapters than the Yoke retainers)?

I think the poor guy will get a new reg from the manufacturer (he has not confirmed it's ScubaPro). The more important question is how significant is the issue and if there is a safety problem with the current first stages design... You see, even if I am 100% confident in my own torquing of the retainers, my regs have still been serviced by various shops in the past. I don't think I have ever seen a torque wrench at any scuba store in the area. And I've seen regulators which I had quite hard time getting the DIN adapters off from without much salt or corrosion traces, which leads me to believe they were over-torqued. It may as well turn out that this problem affects a lot of people. Unless, of course, ScubaPro have taken steps already to address this issue....

 

[redacted]

Retainer design and torque are the same for din and yoke. With both retainers, the shaft of the retainer is larger above the threaded area, about 1 or 2 mm. With the older style retainer this change in diameter occurs with about a 45 degree slope. With the new style, it occurs with a 90 degree slope. This 90 degree slope can engage a similar surface inside the body and help prevent any excess torquing force from being applied and absorbed at the bottom of the opening whicc seems to be the cause of such damage.

I believe Scubapro is blaming the problem on excessive torque being applied during service. Clearly a possibility but I'm not convinced it may not also happen in use when the reg body or hoses are grabbed by boat personnel to lift gear from the water into a boat.

So, how exactly did they modify the retainer to fix the issue? How can one tell the old retainers from the new ones (I am more interested in the DIN adapters than the Yoke retainers)?

I think the poor guy will get a new reg from the manufacturer (he has not confirmed it's ScubaPro). The more important question is how significant is the issue and if there is a safety problem with the current first stages design... You see, even if I am 100% confident in my own torquing of the retainers, my regs have still been serviced by various shops in the past. I don't think I have ever seen a torque wrench at any scuba store in the area. And I've seen regulators which I had quite hard time getting the DIN adapters off from without much salt or corrosion traces, which leads me to believe they were over-torqued. It may as well turn out that this problem affects a lot of people. Unless, of course, ScubaPro have taken steps already to address this issue....

 

[oceancurrent]

Clearly a possibility but I'm not convinced it may not also happen in use when the reg body or hoses are grabbed by boat personnel to lift gear from the water into a boat.

So true! I see this happening a lot. While I try not to let others handle my gear, boat tenders just do it without asking whenever they need to rearrange stuff. I've seen once or twice a guy do this to my gear. Sadly, I have also seen experienced divers grab their cylinders by the regulator. Every time I observe something like this I can't help but feel like I should yell at them.

 

[redacted]

So true! I see this happening a lot. While I try not to let others handle my gear, boat tenders just do it without asking whenever they need to rearrange stuff. I've seen once or twice a guy do this to my gear. Sadly, I have also seen experienced divers grab their cylinders by the regulator. Every time I observe something like this I can't help but feel like I should yell at them.

I don't see it as a big deal on some models. I routinely grab my rig by my Mk7 with zero concern. Even my Mk2 is no big deal. But I avoid it with my balanced piston 1sts (Mk5/10/20).

 

[halocline]

It looks like there have been a few incidents when various ScubaPro regs have cracked in a very similar way. The problem seems to be traceable to cracking of the regulator body at the base of the DIN/Yoke female threads as result of too much tension on the threads from the DIN adapter / Yoke nut. It looks like a very real and legitimate point of concern.

From experience, I know that the DIN adapter needs to be quite snug, otherwise it easily comes loose when the regulator is attached to a cylinder. I tend to tighten it as much as possible with a torque wrench, but I don't seem to get anywhere close to the manufacturer specs.

Just to clarify, by "DIN adapter" you mean the DIN fitting that replaces the yoke on the reg, not an adapter such as the spin-on yoke adapter that allows you to attach DIN regs to yoke tanks. Right?

The DIN fitting and the yoke fitting have the same torque spec, as Awap says it's under 25 ftlbs. Tightening it 'as much as possible' to me would be MUCH tighter than 25 ft lbs.

I'm reasonably sure that the splitting problem was caused by massive overtorqueing of the DIN or yoke retainer. The fix was an "idiot proof" retainer that could be torqued to the point of self-destruction and not place the kind of lateral stress on the reg body that the original retainers could.

If anything, I tend to leave them a little under torque, but I handle my own regs and I'm not too concerned about them loosening. My torque wrench goes to 200 inch/lbs and I just give a bit of an extra tug. No problems so far.

 

[oceancurrent]

Yes, I mean the fitting (ScubaPro "300 bar" Din Conversion Kit for MK16, MK18, MK20 & MK25). "As much as possible" to me means as much as possible with a 90-degree angled hex wrench by hand. Considering that I have to insert the long end into the fitting and I am left with the short end for hand leverage, it's not really that much force. At any rate, I have measured it with a torque wrench and it is below the specs that awap mentioned, so no need to be concerned here. I'd be much more worried about the torquing at repair shops where there is not way to check what's going on, and more likely than not the kid putting together your reg has never heard about the issue of body cracking.

 

[redacted]

I'm reasonably sure that the splitting problem was caused by massive overtorqueing of the DIN or yoke retainer. The fix was an "idiot proof" retainer that could be torqued to the point of self-destruction and not place the kind of lateral stress on the reg body that the original retainers could.

I doubt if that universal retainer fix is idiot proof. It does distribute the torque over additional surfaces and perhaps moves the failure point initially to the retainer. But, as the Captain says, I'm sure a sufficiently talented idiot can still make scrap metal out of a 1st stage.