Scubapro MK20 fatigue cracks..

[will_tekkie]

Hi Guys...Do you know what parts scubapro are changing to avoid the fatigue problems reported at:

http://www.ndc.noaa.gov/pdfs/sb05-01.pdf

of course...the first action must be good tools.. as proper torque to be applied on DIN connectors would be around 266lb-ft ( from SP technical guide)

I know that regs fitted using a Yoke connectors are more proud to fail (SP said due to over-tightening) than DIN ones, but the steps are the same for both?..or simply DIN-fitting regs have not suffered any problems at time?....

 

[Xizang]

Thats a pretty old issue with the MK20. I have an MK20 and never had this problem, the local scubapro distributor here in the Philippines is offering to change the plastic retainer with the ones fitted on the MK25 which is supposedly to prevent that damage when it is over-torqued.

 

[DA Aquamaster]

Scubapapro is replacing the DIN or Yoke retainers on all Mk 20's with the newer universal retainers used on the Mk 25, Mk 17, Mk 2, etc.

This newer retainer has a lip on it that prevents the retainer from stressing the first stage body in the event some moron over torques it. With the old design this could result in the retainer bottoming out in the body causing it to stress the body in the area of the threads.

This retainer was introduced very late in Mk 20 production but for all intents and purposes all Mk 20's are affected.

Updated yoke equipped regs are then given a new plastic trim piece under the yoke that has two grooves in it instead of three to make them externally identifiable as updated Mk 20's. This trim piece is actually the trim piece off the Mk 17.

The SP torque spec for the part is 266 inch pounds - about 22 ft pounds for both DIN and yoke retainers. I suspect given the tendency for long reach allen head sockets to torque substantially under load anyway, that DIN equipped regs are less prone to damage from ham fisted techs.

Plus on a DIN retainer, you have to use a socket/ratchet etc which increases the likely hood that a tech will use a torque wrench and also removes the temptation to just guestimate the torque on a yoke retainer using something like a 16" cresent wrench.

The update is free and is normally done automatically when the reg comes in for annual service.

 

[will_tekkie]

The SP torque spec for the part is 266 inch pounds - about 22 ft pounds for both DIN and yoke retainers. I suspect given the tendency for long reach allen head sockets to torque substantially under load anyway, that DIN equipped regs are less prone to damage from ham fisted techs.

Thanks DA, accurate and outstanding explanation as usual....

Obvioulsly..i made a mistake writing the units. I wrote 266 lb-ft..instead 266 in-ft (30 N-m) :11: i am a metric person..that´s sure!!!! the most times i work using english units for torque are usually related to "heavy duty machinery"..so lb-ft are the most common even in the deep of my mind.......

We can also think that NOAAs guys do not care too much their regs..Excessive torque is a bad thing for all mechanism specially those made with ductile materials...

 

[DA Aquamaster]

I wondered about the techs working on the NOAA regs when it was first announced since they had such a large problem with them. Of course as it turned out, some SP shops also had techs who did not bother with torque wrenches, so it did highlight an industry wide problem. Since few shops carry only SP equipment, it was an industry wide issue.