either or

[rstofer]

Do the math. Just ratio CF vs pressure. CF / <design pressure> * <fill pressure>

Unfortunately, you might get a fill like that in Florida.

Richard

 

[HowardE]

Hi,
I was wondering what would be major differences between lp 95's and hp100's, besides the pressure. As someone who would double them up later on, which has better characteristics for a wreck diver? Fills are no problem in 3500psi and 2800 psi. I would like to hear from cavers and wreckers please, it would be a great help.
Thanks in advance

Here's a nice chart from Joel's store - Scuba Cylinder Specifications

The difference in tank characteristics is detailed here.

From what I understand. TRUE HP TANKS are 3500 PSI. The current HP tanks have a service pressure of 3442 PSI - which allows them (because of a US DOT Exemption) to use the 200 bar valves and burst disks as opposed to the 300 bar valves.

The 3442 psi DOT Exemption cylinders have the same length, diameter, and capacity at lower 2640 psi pressure as the 3AA cylinders.

Lower pressure tanks are easier on the equipment, and the tanks.

Some divers take those risks (overfills) when making decisions to do wreck penetrations or cave dives.

SB User DAAquamaster may know more specific details here.

 

[Jim Lapenta]

It depends on where you are and what your specific needs are. Filling LP tanks to 3000-3500 psi is common in cave country and in many wreck diving destinations. Steel tanks are hydro'd to 5/3rds of their working pressure and with 2640 tanks that's 4400 psi. They are designed to withstand this for 1000's of cycles. The same tanks in Europe are rated to 4000psi and they do not use burst discs in many countires. Filling my lp's to 3500 for one or two dives and then taking them to 3000-3200 for regular use doesn't bother me at all. Especially since I am using burst discs. Why do you think they have discs rated at 3000, 3500, etc. The ones in my 85's and 95's are 5000psi discs. 3500's in the lp72's. These discs came out with these ratings before HP tanks became popular. If you go to the Fla springs I'm sure you'll also find bolted tanks( No burst discs at all just a ss bolt) and reading 4000psi at the beginning of the dive.

 

[dori fish]

Thank you
so i can fill a lp 108 to 3500 psi or no b/c i am looking to buy tanks

 

[rongoodman]

The 95 is bigger around (8" vs 7.5") but shorter in height than the 100 by 3" or so. If you are short stocky person doubling the 95 might be the way to go other wise the 100 would probably trim out better for a taller person. IIRC correctly HP cylinders tend to be favored by NE divers as they are also a bit more negatively buoyant than LP. So less need for extra lead with a dry suit.

The Worthingtons are the same length, 24" each. The empty HP100 is -2.5 lb, as opposed to -1 lb for the LP95.

 

[HowardE]

Thank you
so i can fill a lp 108 to 3500 psi or no b/c i am looking to buy tanks

You can. If the shop will do it. Some shops WILL NOT do it - because it exceeds the specified service pressure for that tank.

 

[rstofer]

There are Federal laws that govern how tanks are to be filled and the number one law is DO NOT fill it beyond its service pressure.

There are two considerations: First, do you want to risk overfilling your tanks and second, can you find someone to do it? With luck, nobody in your area will do it.

Why not just buy the HP tank in the first place?

Look beyond capacity. Look at weight, diameter, buoyancy, trim and any other characteristics that make a tank suitable. Some LP tanks are so negative they might as well be boat anchors. Other LPs are more buoyant than HPs and that may mean you not only have a really heavy tank but that you also have to add lead compared to the HP setup.

Richard

 

[dori fish]

What is the risk of overfilling lp tanks

 

[rstofer]

What is the risk of overfilling lp tanks

We just argued this, it comes up every month. Using the Search feature, I found a few threads.

Here's one: http://www.scubaboard.com/forums/tanks-valves-bands/299744-service-pressure-steel-72-a.html

Here's another: http://www.scubaboard.com/forums/basic-scuba-discussions/298889-overfilling-scuba-cylinders.html

There's nothing that could possibly be added...

Richard

 

[Scared Silly]

... Steel tanks are hydro'd to 5/3rds of their working pressure and with 2640 tanks that's 4400 psi. They are designed to withstand this for 1000's of cycles. The same tanks in Europe are rated to 4000psi and they do not use burst discs in many countries.

I have the heard "The same tanks in Europe are rated to 4000psi" many times. This statement is one of the great internet scuba myths. However, in discussions with Lee at Sea Pearls who was the importer for years for Faber he has said that this is definitely not the case. Same physical size but different material.

BTW - I just picked up an LP95 and LP108. Paid under $300 both with three left on the hydro. No valves but I had two H valves just waiting for a new home.