Advice Needed buying reg

[Genesis]

If 'ya fill 'em with silicone that'll prevent freezes quite reliably. Its also extremely dangerous if you have high FO2 mixes in that tank. If the HP piston ring leaks on you, which just happens to be the highest-wear O-ring in the entire regulator, it is entirely possible to get an instant fireball. Its PROBABLY ok with FO2s up to 40% (but you can't quote me on that) but on a deco bottle its damn dangerous. If you're going to do that on a deco bottle please use the $25 worth of Christolube instead!

I don't believe in the AF crap, and I hate the mess that filling the environmental chamber makes when I go to tear it down the next time, ESPECIALLY since I O2-clean EVERYTHING and ANY trace of Silicone left in there is unacceptable.

I have several of the environmental trim rings here, but you won't find one on any of my regs - indeed, I tore off the rubber trim rings on ALL my SP firsts (including the "regular" ones), because they (1) trap salt water, which means corrosion, and (2) impede free and full flow of water through the balance chamber. To freeze you must have water that SITS long enough to freeze AND low temperatures - the better the flow rate through the holes, the harder it is to make the reg freeze. The only one I leave on is the one on the adjuster/end-cap end of the Mk20/25s and the plastic bezel where the yoke or DIN adapter screws in - the other two come off immediately.

I'd rather leave the composite piston and "AF bushing" garbage out and fill the chamber with Christolube, and I bet it'd work well too - and be totally non-approved

BTW lowering the IP doesn't help much. All it does is lower the maximum flow rate of the reg, which is high enough on the SP piston firsts to hose you anyway, even cranked down to 125. For the older Mk10s, BTW, there are THREE seats in a rebuild kit - a judicious selection of the one to use will result in a lower IP, and if you get "cute" you can actually use at least two of the three seats in one kit by changing the shims and seat you install. For the DIY guy this means you get two rebuilds out of one kit, since O-rings are easily sourced. Finally, the Mk10+ and Mk20/25 appear to use the same seat - I can't verify they actually ARE the same, but they sure as heck LOOK identical

I really LIKE the older Mk10s. They don't recover quite as fast as the 10+/20/25, but I can't tell the difference when breathing off any of the four which is on the other end.

BTW for my "test", if anyone wants to take me up on it, there won't be no wimpy tank on the other end. It'll be a HP120 with a nice, full, cold fill - right to 3442 psi. I consider it cheating to use a LP tank, as that limits the adiabatic cooling available.....

 

[Wendigo]

Save some more money up and get an Apeks ATX 200. You wont be sorry.

 

[DA Aquamaster]

A 2 oz syringe of the general purpose christo lube MCG 129 is enough to fill five or six Mk 10 ambient pressure chambers and is really not that expensive even in this appication at about $20 per tube. It is also a little thicker and stays put better than most other silicone greases. The silicone originally used by SP in SPEC chambers was a little thicker than what is normally available off the shelf anyway. Packing the chamber properly is important to reduce the occurrance of air bubbles and proper packing also reduces the concerns about trapping salt water whether a SPEC boot is used or not.

Personally I have good results with Dow 111 silicone on my primary regs but then I tend to dive air or Nitrox 32 or 36 most of the time. I will use hotter deco mixes but then I also use MK2 first stages on them and I have found the normal TIS kit to be more than adequate for the 50 scfm flow rate that it is capable of producing so normal O2 clean procedures and lubricants are in use.

The Mk 10 Plus and Mk 20/25 all use seat #10-101-161 and IP adjustment on the Mk 10+ and Mk 20 is done with a maximum of 3 shims under the lip of the seat retainer and a maximum of 3 more in the ambient chamber (normally 2 below and 1 above the spring) all of which will increase IP by about 5 psi per shim. The only way to lower IP on a Mk 10 or Mk 20 if it is still too high after all the shims are removed is to change to a slightly softer spring. The Mk 25 incorporates an IP adjustment screw in the seat retainer.

I have noted with the occassional Mk 10 spring that they seem to get a bit stiffer with age. I'm not sure if this is due to work hardening or some other factor, but I do seem to have to replace a spring now and then on Mk 10 Plus regulators. On a standard MK 10, the higher seats included in the current annual service kits put the soft seat closer to the piston knife edge and reduce the distance the piston travels and consequently reduces the spring compression and the in turn the intermediate pressure. I supsect SP has started including these additional seats to reduce the number of springs that would otherwise have to be replaced to keep the IP within the approved range.

In my case I will swap the spring in my Mk 10 Plus with a slightly softer one from one of my shimmed Mk 10's and then use a higher seat in the Mk 10 to enable the use of the stiffer spring.

The knife edge seat on the Mk 10 and on the early Mk 20 and current composite MK 20/25 pistons offer a firmer lockup with less creep than the rounded edged sealing surface on the MK 10 Plus and brass tipped MK 20/25 pistons. In my opinion if you have one of the middle production brass tipped pistons it's worth the upgrade to the current composite piston AF advantages aside.

 

[qmahmud]

jetstream all the way