Finally think i've decided on steel.....

[Quarrior]

So, you're probably aware that when a gas is compressed, the temp. of a tank is heated because of the condensing of the molecules. The reverse is true as gas is "uncompressed" - it gets cold (sometimes extreemly cold) as it expands. THis is basic physics. So the higher the pressure differential, the more this happens (this is how your A/C works).

You are correct in your statements, however, that is only in a case of a free flowing environment, not a sealed valved controlled environment. Unless the reg free flows, the amount of gas passing through it at any time is to restricted for this "chilling" effect to take place.


I do agree that you want a cold water reg. What does he have/dive?

So here is an example. Most people will probably agree that Scubapro 1sts are not cold-water regs. But there are plenty of cases that will show you that when a scubapro 1st is combined with a LP steel tank, freezing is never a problem. It only shows up when the tank pressure is ~3000+ PSI.

I would think this is something for the equipment manufacturer to investigate and correct, if it happens this way. I know the regs that I mentioned do not have a problem on HP tanks.

Higher pressures are harder on the lubrication and parts in general. If you use HP tanks, your maintenance cycle for your regs (1st stages) should be more frequent (assuming you are an active diver).

Interesting, I had not considered this.

While I'm not one of them, some divers will swear that you are required to use a HP DIN connection if using tanks beyond 3000 PSI (IE - can't use a std. yoke).

I tend to agree with you in the case of the newer regs. According my LDS the yoke on my Zeagle is rated to handle the HP tanks I use it one. Although, I will be switching to DIN in preparation for moving to doubles.

 

[jhelmuth]

You are correct in your statements, however, that is only in a case of a free flowing environment, not a sealed valved controlled environment. Unless the reg free flows, the amount of gas passing through it at any time is to restricted for this "chilling" effect to take place.

I am no expert, but I do beleive that it is in fact the case (not exclusively that is), even if is not a free flowing environment. BUT THAT IS NOT BASED ON MY EXPERIENXCE (I hate cold water!). This is based upon others reported experiences. I do agree that a free-flow (heck - even rapid inflation from your BCD inflator) does makes this happen more readily. For cold water diving, especially with HP tanks, I'd have to choose an H-valve config with redundant reg for safety.

 

[Ann Marie]

You decided to buy a steel tank right when finding steel tanks is very hard. They are sold out almost everywhere.

Good luck finding one. I hope you find one.

Xanthro

I just bought a PST 80 from scubatoys.com. I think they had one left, if someone hasn't already snapped it up. Delivery was quick too.

 

[kawboy579]

I have no experience with cold water icing, but, from a physics standpoint, the pressure should make a difference regarding the amount of cooling that takes place. As a gas expands from a compressed state, it cools, and the rate of cooling has to do with several factors including the gas in question, the total pressure change, the amount (volume) of gas involved, and the number of molecules of gas. for this purpose though, all that matters is that the volume is expanding, and it expands more coming from a higher pressure.

1/4 liter of gas expanding from 3000psi expands a whole lot more than 1/4 liter of gas expanding from 600psi. This is because at 3000 psi, the gas goes from a very small volume to 1/4 liter, wherease at 600 psi, it expands from a larger initial volume to 1/4 liter, therefore it cools less. This is the same principle as how an air conditioning unit works (high pressure refrigerant expanding to atmospheric pressure). Sorry for the long reply, but this seems to make sense. Whether or not it works like this in reality can be a whole other story.

 

[yknot]

Anyone had any experience with these:

Yes. The OMS tanks are made by Faber but per the OMS web site, are rated at 10,000 fill cycles at 4000 PSI. The OMS branded valves are as good as any I've seen, also. Being in Michigan, don't worry about a lack of galvanizing, like PST uses. Your tank likely will never see salt water and I haven't seen any problems with mine or some buddies tanks. I would suggest starting with a RH valve (V103). These have a threaded insert that can be removed and then the tank would work with a DIN valve, HP vs LP issues aside. An OMS RH valve has a deadend/capped side post. If you doubled this tank at a later time, you would need a tank with an OMS LH valve plus a cross over manifold of your choice. The basic RH valves can also be converted to 'H' style. You can probably find a LDS that will match LeisurePro prices on a tank, when shipping is added in. A LeisurePro tank will also a visual.

 

[yknot]

Anyone had any experience with these:

Yes. The OMS tanks are made by Faber but per the OMS web site, are rated at 10,000 fill cycles at 4000 PSI. The OMS branded valves are as good as any I've seen, also. Being in Michigan, don't worry about a lack of galvanizing, like PST uses. Your tank likely will never see salt water and I haven't seen any problems with mine or some buddies tanks. I would suggest starting with a RH valve (V103). These have a threaded insert that can be removed and then the tank would work with a DIN valve, HP vs LP issues aside. An OMS RH valve has a deadend/capped side post. If you doubled this tank at a later time, you would need a tank with an OMS LH valve plus a cross over manifold of your choice. The basic RH valves can also be converted to 'H' style. You can probably find a LDS that will match LeisurePro prices on a tank, when shipping is added in. A LeisurePro tank will also need a visual.

 

[kawboy579]

Yeah, i dont plan on using it in salt water. If i go to the ocean, it will be for some sort of trip, and ill just rent tanks there. As far as size goes, would you buy the 98CF and run it at higher pressure (say 3000 psi instad of 2500), or buy like a 118CF or something of the sort?

 

[teknitroxdiver]

I wouldn't get the OMS tank, I'd get a PST 130. Tons of air for a dive, and good doubled up. If you don't want one that big, get either the 120 or the 119. All of these are good doubled up, but some don't like the 119 as doubles.

 

[jhelmuth]

I wouldn't get the OMS tank, I'd get a PST 130. Tons of air for a dive, and good doubled up. If you don't want one that big, get either the 120 or the 119. All of these are good doubled up, but some don't like the 119 as doubles.

Why would anyone take a tank that is so large, you can't even use up half the tank by the end of the dive? Do you use that much air/gas? A reserve is understandable, but it seems that that is taking it to the extreem.
If you dive a larger tank (more weight), you'll be working against one of the things you've worked hard to have in control - bouyancy and air consumption. I can understand a 100 for deeper dives, but a 130 is just huge.

 

[Mo2vation]

Why would anyone take a tank that is so large, you can't even use up half the tank by the end of the dive? Do you use that much air/gas? A reserve is understandable, but it seems that that is taking it to the extreem.
If you dive a larger tank (more weight), you'll be working against one of the things you've worked hard to have in control - bouyancy and air consumption. I can understand a 100 for deeper dives, but a 130 is just huge.

The tank is weightless underwater (essentially) so what is the burdon? It dives as effortlessly as a tiny HP80. My SAC when carrying my 130 is no different than when I dive my HP100.

I have excellent trim, buoyancy and control with my waterheater. Its no different than my HP100. As is evidenced by my SAC, my watermanship and my in-water performance.

I have peace of mind of knowing I got lots of gas. I never plan to back into the whole can.

PLUS, by primary buddy dives a 130, as well. So we go in, and come out about the same. He hoovers about 500 - 700 more than I do. Makes sense, he's bigger than I am. My wife dives the HP100 - so I come up with about 900 - 1000 extra. Sometimes less... what's the big deal?

Your arguement doesn't make any sense to me. For what ever reason would a person choose to carry less gas than they comfortably can carry? Heck, I even shore dive with this thing, schlepping it across the sand in the So Cal heat in a drysuit. Its no biggie. Of course, I prefer to boat dive wif it (flop in, climb out) but I can carry it, so I do.

The 130 is simply the best choice for the cold water diving I do. Period.

K