MK10 rebuilt and theres an issue

[ba_hiker]

Just got my stage bottle regulator serviced. Its a Scubapro MK10 first with a S390 second. Bought it used and have used it a couple of years. Had it serviced twice before, for oxygen service and there was never a problem.

This time i take it to a LDS which I trust and the repair tech says it can't be made O2 clean. He says only SP MK10+, MK20 and MK25 have O2 rebuild kits and the plain MK10s have HP seats that are not suitable for O2 service. Further the seats for Mk10Plus (nitrox and HP O2 ready from SP) are usable with HP O2, but will not fit the plain MK10.

Anyone know about this? Is there something more that I am missing? Is there a fix for this (other than a new 1st stage)?

thanks

 

[DA Aquamaster]

Is true that the Mk 10 uses a different seat material and it is true that SP does not certify for O2 use, but on the other hand, Mk 10 seats are not failing in service due to high O2 exposure nor are they busting into flame. Like O2 clean, O2 compatible materials are a matter of degree as just about anything will burn in a 100% o2 environment with a high enough ignitition temp. Safety comes more from preventing ignition than it does from reducing fuels.

More importantly, any Mk 10 can be converted to a Mk 10 Plus. All it takes is a new Mk 10 Plus piston, spring and Mk 10 Plus seat retainer. Dealer cost is probably less than $40 for the parts.

It is not exactly cheap but it is not expensive either and is much cheaper than buying a new first stage.

 

[Packhorse]

But with the issues of IP creep with the MK10+ is it better to convert to the + or just O2 clean the old mk10 and hope for the best?

 

[Couv]

I knew the MK 10 and the + had different seats, but did not know they were different material. If I am not mistaken, the MK 10 hp seat is made from an O2 compatible material (Teflon.) DA, by chance do you know what material the Plus hp seat is made from?

Personally, I prefer the regular 10 over the Plus because the parts count is lower. No extra bushings, guides etc. In fact that makes me wonder why the shop would think the Plus is a better choice for O2 service. Not only are there more parts to clean, they are soft, thin parts which would just add more ignitable material. I'm sure there are more current bulletins, but ScubaPro Engineering Bulletin #271 (May 2001) states that the only regulator appropriate for O2 percentage greater than 40 percent is the MK 20

I would go back to the shop that originally O2 cleaned your MK 10 and have them service it again and perhaps fill you in on the ends and outs of O2 cleaning. Of course, you can always come to the Dark Side and Do It Yourself.

As an aside, for a very high FO2 regulator, a simple non balanced piston 1st stage such as the Scuba Pro MK 2 is probably a better choice. DA articulates it well in this thread.

http://www.scubaboard.com/forums/regulators/189796-auqalung-legend-100-o2.html

c

 

[ba_hiker]

Thanks everyone thats commented so far. The reg has O2 compatible rings in it and cristolube for all parts. There is a SP service note in a tech manual (which was shown to me) that said that the Mk10 was not for use above 40% O2, and that the Mk10plus, Mk20 and Mk25 were (when appropriately cleaned and lubed).

 

[drbill]

No extra bushings...

And just what is wrong with having an extra bushing or two?

Seriously, this is good information. Thanks for posting it. I use Mk10's and Mk10+ first stages almost exclusively (I have five).

Dr. Bill Bushing

 

[Couv]

Dr. Bill,

;-) No one ever accused you of being extra, extraneous, superfluous.... Besides, you are an external Bushing.

Do you use a MK 10 for > 40 % O2 If so, is it the Plus or Standard?

c

 

[Packhorse]

I do recall seing a pic of some dive show in europe that had a MK2 nitrox reg in it with M26 thread so I assume you can now get a O2 service kit for the MK2 as well.

 

[DA Aquamaster]

I am not sure exactly what seat material is used in the Mk 10. I do know that 3rd party vendors had viton kits available for Mk 5 and Mk 10 regs intended for high percentage O2 use long before SP made even the Mk 20 nitrox available.

Despite their hisotry of use in that application, I have not heard of any O2 fires in the Mk 10 related to the seat material. The other potential issue is that a seat may degrade over time with high O2 exposure. However while seat material is critical in a valve due to constant exposure at high partial prssurs, I think it is a minimial concern in any reg as the exposure time is quite low.

That said, using a Mk 10 for nitrox over 40% is still not Sp sanctioned and it would be considered something you do at your own risk.

SP can approve what what they want for O2 service and if they have the Mk 10 Plus option available, they have no incentive to approve the even older (and upgradeable) Mk 10.

The Mk 10 Plus uses the same seat design as the Mk 20/25 - essentially a smaller o-ring sealed seat as opposed to a concave faced hockey puck.

I initially converted my Mk 10's to Mk 10 pluses when the conversion kit became available and immediately regretted it as seat life was very poor. But to be fair, the seat material has been changed and improved so I don't think the original reliability issues are the concern they used to be. Customer Mk 10 plus regs now come in for annual service working just as well as regular Mk 10's.

The lock up on the Mk 10 plus is also better than it was on the mid production Mk 20, where a similar piston and seat design was notorious for mushy lockup and IP creep.

If your tech is not giving you over 40% approval for a Mk 10 he is consistent with Sp policy and its hard to ask him to accept the liability of exceeding their limits.

But he probably should have advised you of the Mk 10 to Mk 10 plus upgrade option as more or less part of the O2 clean process.

The same argument more or less applies to the Mk 2. From a design perspective it is an excellent choice for a deco reg, but Sp won't committ to using it in that manner (at least in the US) - preferring you buy a more expensive reg approved for that purpose.

The M26 sounds great but in my experience what is available in Europe is often never made available in the US - possibly due in some cases to product liability concerns and in other cases probably due to their marketing strategy in the US. In any case I have not yet seen an O2 service kit for the Mk 2.

 

[Couv]

I do recall seing a pic of some dive show in europe that had a MK2 nitrox reg in it with M26 thread so I assume you can now get a O2 service kit for the MK2 as well.

Hi Packhorse,

The bulletin I referred to states that all MK2+, MK16, MK18, MK18UL,MK 20, MK20UL sold after Oct 2000 are approved for Nitrox up to 40% straight out of the box, so I would think a conversion could easily be made for the same models, but I think the OP is interested in O2 SERVICE which means "oxygen clean" and safe for 100%. As DA points out, SP has only APPROVED the MK20 for that.


couv