Ok, here's a good one.
Deco regs. High F02 mixes.
All the seats I've seen appear to have been made out of nylon - even those intended for Nitrox service.
Well folks, that ain't the best material for high FO2 mixes, and what's worse - maybe a lot worse - is that the HP seat orifice is likely sonic during actual use.
In laymen's terms this means its where you could get an ignition event with a high FO2 mix.
It doesn't seem to happen very often, so the question becomes - is there some reason that seats aren't made out of something like KEL-F, or it just that the real issue is more one of cleaning than material compatability?
Ditto for valves - finding a manufacturer that will actually specify that a particular valve has O2-compatable components (leave O2-clean out of it - I can do that myself) is a real problem! Thermo, for example, has their "nitrox" valves, but then turns around and says "up to 40%" (!) and the seats in those (I own several) sure as hell look like the old Nylon 6/6 again!
I know that there HAVE been valve flash incidents with high FO2 deco mixes when valves were turned on. Chickdiver had one, for example.
So what's the poop here? I've seen "official" manufacturer documentation and its nearly completely silent on this point, or falls back on the "40%" stuff.
Obviously people ARE using deco tanks, and ARE using deco regs. So is there some "secret" source for compatable seats, or is this whole thing somewhat overblown - make darn sure its O2-clean....
I know there are folks who are perfectly comfortable with regs from both Apeks and SP being used in deco service - the LP side I'm not concerned with. Its the HP side. Having looked at the kits, including the so-called "nitrox" ones that some manufacturers sell, all they appear to be doing is putting in either EPR or Viton O-rings, and most manufactuers appear to have gone to either EPR or in some cases polyurethane (where hard, extrusion-resistance is required - ala the HP piston ring on a SP Mk25) instead - thus, all the "nitrox kit" appears to be, in many cases, is a bezel or trim ring that says "nitrox" with the same stuff in it that would otherwise be in a standard kit!
(Yes, I know there is no such thing as a soft good such as a seat that won't ignite or decompose if temps get high enough in a high FO2 atmosphere, and that temps at a "blind corner" can reach 1500F or more if you're injudicious about how fast you own valves and such. Just wondering what's REALLY being done here by the various manufacturers... because what I can SEE from inspection looks like they're not going as far as they might be able to.)
Deco regs. High F02 mixes.
All the seats I've seen appear to have been made out of nylon - even those intended for Nitrox service.
Well folks, that ain't the best material for high FO2 mixes, and what's worse - maybe a lot worse - is that the HP seat orifice is likely sonic during actual use.
In laymen's terms this means its where you could get an ignition event with a high FO2 mix.
It doesn't seem to happen very often, so the question becomes - is there some reason that seats aren't made out of something like KEL-F, or it just that the real issue is more one of cleaning than material compatability?
Ditto for valves - finding a manufacturer that will actually specify that a particular valve has O2-compatable components (leave O2-clean out of it - I can do that myself) is a real problem! Thermo, for example, has their "nitrox" valves, but then turns around and says "up to 40%" (!) and the seats in those (I own several) sure as hell look like the old Nylon 6/6 again!
I know that there HAVE been valve flash incidents with high FO2 deco mixes when valves were turned on. Chickdiver had one, for example.
So what's the poop here? I've seen "official" manufacturer documentation and its nearly completely silent on this point, or falls back on the "40%" stuff.
Obviously people ARE using deco tanks, and ARE using deco regs. So is there some "secret" source for compatable seats, or is this whole thing somewhat overblown - make darn sure its O2-clean....
I know there are folks who are perfectly comfortable with regs from both Apeks and SP being used in deco service - the LP side I'm not concerned with. Its the HP side. Having looked at the kits, including the so-called "nitrox" ones that some manufacturers sell, all they appear to be doing is putting in either EPR or Viton O-rings, and most manufactuers appear to have gone to either EPR or in some cases polyurethane (where hard, extrusion-resistance is required - ala the HP piston ring on a SP Mk25) instead - thus, all the "nitrox kit" appears to be, in many cases, is a bezel or trim ring that says "nitrox" with the same stuff in it that would otherwise be in a standard kit!
(Yes, I know there is no such thing as a soft good such as a seat that won't ignite or decompose if temps get high enough in a high FO2 atmosphere, and that temps at a "blind corner" can reach 1500F or more if you're injudicious about how fast you own valves and such. Just wondering what's REALLY being done here by the various manufacturers... because what I can SEE from inspection looks like they're not going as far as they might be able to.)