Upgradability/future options on a LP steel 121

[jonnythan]

lp 120s can hold 400 cu ft

At 4400 psi, which is an 83% overfill

 

[lamont]

2. you can get a complete fill off a crappy compressor

I still don't understand this "complete fill" fixation at all.

Water volume of tank * max fill pressure of compressor == air capacity of tank

If you're not shy about overfilling LP tanks, then HP or LP makes no difference in that equation. Buy a tank with the water volume that gets you the capacity you want at the fill pressure you can get. If you are shy about LP overfills then LP tanks are always worse since they're heavier for the same final air capacity (assuming your compressor can get above 2640...). The only exception to this is the LP120, since nobody makes an HP-149.

Just because you get 3200 psi fills on an E8-119, why do you feel like you're getting ripped off and you'd be better with an LP120 so you can get the rated fill? LP120s are freaking heavy tanks -- if an E8-119 @ 3200 psi gets the job done, stop stressing out about the 300 psi that you're missing...

- Cost is a valid benefit of LP tanks
- You can't beat the water volume of an LP120
- Some find the buoyancy, trim and stability characteristics of LPs more to their liking

But going with LP tanks because you cant get a 3500 psi fill every time is silly...

 

[EricPuryear]

Thanks again for all the help - I think I'll go for a HP steel 120 since it is only $10 more:

http://66.225.239.89/~scuba/tdl/nst...id=654&zenid=88ae1a80346713ec64a81a0b4a16e005

I emailed the site operators about getting a K valve, and the response was:

Dear Eric,

When you place the order just request in the comments box that we give you
a SOS PRO/DIN/K valve and that will work for you. All tank orders now due
to the very high volume of orders we are processing will take a week to
leave our warehouse. Once it leaves it will take UPS about 4 days. So
figure two weeks now.

Thanks
Joel Silverstein, VP COO
Tech Diving Limited

So let me make sure I'm understanding this correctly, based on what I’ve read on this site and asked other people, as I'm pretty new to SCUBA equipment (I got certified in February)...

1) I can order the tank with the SOS PRO/DIN/K valve, and that will work with my current regulator, a Sherwood Blizzard with the yolk connector, as well as any DIN equipment I purchase at a later date.

2) This valve assembly is OK for use with Nitrox.

3) When I get the tank, I will need to take it to my LDS (who won’t be happy I didn’t buy from them ) for a visual inspection. After that I can use it.

4) Finally, does anyone have any comments on the tank manufacturer, manufacture date (2004, but brand new) or the retailer?

Sorry for all the questions, I just want to make sure I have all this correct.

 

[markfm]

Edited -- the post about 400 CF of course must have meant for doubled-up 120s...

 

[jonnythan]

One thing to be aware of is that HP 120s are very very long tanks. They're almost 3 full inches longer than Al80s. I'd *really* recommend that you consider the HP100's or LP108s or LP95s. They are really more than enough gas and they are nice manageable sizes.

 

[California Diver]

i hear the lp85s are really, really nice tanks. yes 400 cu ft in double lp 120s. as far as getting a complete fill you cant get a complete fill in a hp130 off a compressor that only fills to 2600 psi. on a set of lp 121s you can get almost a complete fill

 

[jonnythan]

i hear the lp85s are really, really nice tanks. yes 400 cu ft in double lp 120s. as far as getting a complete fill you cant get a complete fill in a hp130 off a compressor that only fills to 2600 psi. on a set of lp 121s you can get almost a complete fill

Out of curiosity, are there really shops that routinely fill LP tanks to 4400 psi?

HP/E130s are physically much smaller than LP 120s and hold 113 cf at 3000 psi anyway.

 

[pdoege]

Out of curiosity, are there really shops that routinely fill LP tanks to 4400 psi?

Sigh, there used to be....

Grumble....

Anyway, by the time someone has sucked down cave filled LP121s the deco obligation isn't really fun.

Remember that you can also carry stages. Safer than putting all of your eggs in backgas.

Not too mention that with gas matching you can only use as much gas as the guy with the smallest tanks.

Peter

 

[lamont]

take those 4400 psi filled LP121s and throw an RB80 in the middle of them and with an 8x factor for the SCR you'd get as much bottom time as 3200 cu ft of gas...

 

[Tom Winters]

Thanks for all the help! I'm not too concerned about the weight of the tanks (I'm 6'2" and 220 lbs) but I do care about the size.

According to the charts I've looked at, an AL80 has a diameter of 7.25 inches and a lenght of 26.1 inches, while the LP steel 120 has a diameter of 8.00 inches and a length of 29.2 inches. That doesn't seem too much bigger... Am I missing something, or is an additional 0.75 inches of diameter and 3.1 inches of length a lot?

Also, do you think that the lower pressure of the LP 120 is "better" for my hoses and regulator?

The extra length of the LP121's a royal pain to carry by the valve. You have to bend your elbows to clear them off the ground, and after a while, it starts to kinda tire you out so then you have to cradle-carry them so that means one tank at a time.
From a mechanical point-of-view, the lower pressures are actually better for a lot of first stages if you use Genesis valves or are a valve snapper-open. This is as opposed to slowly opening the valve and pressurizing the regulator. This is easy to do with Thermo or Sherwood valves, but Genesis valves snap right open when you turn the knob and this can cause premature wear on first stage components.
One of my LP121's weighs 58 pounds with 3600psi in it. It's heavy, but that's as much gas as is in twinned aluminum 80s. There are guys who dive with twinned 121s, and there are guys with bad backs who used to dive with twinned 121s. Each year, one list gets bigger. Once you mess your back up from overtanking, it's a tough recovery. If you need twins, I love the twinned LP85s. Each tank weighs less than an aluminum 80 and can hold 115 cubic feet of gas. When you start needing more than 230 cubes of gas with deco bottles, maybe you need to start thinking rebreather.
They cost a mint even now, but try pricing back repairs.