Scubapro Mk25T and Nitrox

[Pinetree]

Hi everybody

I recently bought one of the new Scubapro Mk25T + S600T regulators.
I am very happy with it but concerned about something I heard: a maintenance tech from a local scuba shop was told in a Scubapro sponsored course that this model could/should not be used with Nitrox.

I found no reference to this fact in the user manual.

I am certified (TDI) for Advanced Nitrox and Decompression Procedures dives and regularly dive with gas mixtures up to EAN40 in my Main tank (where I plan to use the Mk25) and up to EAN60 in my stage tank (where I use a different, oxygen ready regulator).

Does anyone have any information on this subject?

Best regards

 

[canuckton]

Your reg needs to be rebuilt with Viton O-rings.

Generally, Spro uses halocarbon (non-reactive) grease on their regs in manufacture (christolube, actually) but their regs are not "EANx Ready."

The rebuild kit is about $50, and a good technician needs to do the rebuild, someone who understands what they are doing (Viton is not as supple as some of the silicon compound orings that Spro uses) and how to examine the cleaned parts.

Spro sells EAN regs, designated by cool green and yellow plastic bits and knobs. The kit comes with these.

C

 

[Scubaroo]

Isn't the issue here the fact that the Mk25T is a titanium regulator, rather than the type of o-rings or lubricant?

 

[ckharlan66]

I have also heard that there is a problem with titanium and O2. I was curious as to the specifics.

Chad

 

[Scubaroo]

Had a quick browse on the web - coudn't find anything really specific to Nitrox, but a few mentions were made of titanium's unsuitability in high O2 pressure environments due to combustion risk. Also a few mentions of several serious fire incidents with a particular aluminum oxygen regulator for medical use that resulted in a recall (different metal, same problem). So it sounds like it's out for diving with 100% O2 on a deco bottle, but it's probably best to contact Scubapro's support folks with the direct question:

SCUBAPRO/UWATEC
1166 Fesler Street
El Cajon, CA 92020

(619) 402-1023

 

[Goldminer]

The Scubapro website mentions an available 100% O2 compatibility kit for the MK25 but does not mention its availability for the MK25UL or MK25T.

http://www.scubapro.com/consumer/products/regulators/firststages/mk25/mk25.html
http://www.scubapro.com/consumer/products/regulators/firststages/mk25ul/mk25ul.html
http://www.scubapro.com/consumer/products/regulators/firststages/mk25t/mk25t.html

Maybe it's not oxygen compatible.

 

[Pinetree]

Thank you all for your replies.

I've had more valuable input from you than from anyone at Spro that I've contacted!!!

Since my first post, someone suggested that the problem with titanium and Nitrox, or more particularly O2, might have to do with spontaneous combustion of this metal at high O2 adiabatic pressures (namely the pressure shock that develops when you first open the tank valve and pressurize the 1st stage).

As to the O ring composition, I have been using my trusty old Mk20 with up to EAN40, with no problems (it is serviced at least once a year and the service guy says that it's fine).

Thanks everybody

 

[Scubaroo]

namely the pressure shock that develops when you first open the tank valve and pressurize the 1st stage

You can reduce this pressure shock by cracking the valve open slowly - just like you'd slowly open a can of coke that had been shaken or dropped (unless you were deliberately aiming it at someone :tease: (the coke, not the scuba tank!)).

 

[canuckton]

The titanium-nitrox thing is a bit of a myth.

yes, given sufficient heat, a spark, and a pure o2 environment, titanium will combust. But so will marine brass and stainless steel. At considerably lower temperatures, in fact.
So will copper, invar, and inconel.

Use your Ti reg with nitrox with confidence. It will not combust. Brass sparks more than Ti. Remember that adiabatic decompression keeps the reg cooler as well. I would be surprised if one could release nitrox (even 50%) across a regulator orifice at speeds sufficient to create titanium sparking.
Not only that, but a Mk. 25 has a "blunt" orifice and tapered seat, so the likelyhood of creating a fire in an O2 clean piece of kit is pretty remote.

Interestingly, pure O2 flows through many titanium parts in aviation O2 systems, including valves.

C