LP & HP tanks

[yukoneer]

Since HP tanks are now readily available from most manufacturers, and affordable - why are people still buying LP tanks instead?

just curious.

 

[ShakaZulu]

Hmm, let me think.......

1. Price

2. Compressor requirements, some shops can't fill to HP pressures

3. Bouyency charactiristics for doubles

ect.

 

[jonnythan]

Because they're cheap, and that's what the local shops have. E-series and X-series tanks are hard to come by, and the old HP tanks are narrow and not necessarily good choices.

A couple of online shops are closing out Faber and Worthington LP tanks for ridiculously low prices and moving a ton of them... and most shops that even have steel tanks still have the LP tanks in stock, and few to no 3442 psi tanks, so that's what they tell people to buy.

 

[jonnythan]

Hmm, let me think.......

1. Price

2. Compressor requirements, some shops can't fill to HP pressures

3. Bouyency charactiristics for doubles

ect.

1) is perfectly true.

2) and 3) don't make sense because the newer "hp" tanks are the old "lp" tanks rated to higher pressures. 3000 psi in an LP95 is 3000 psi in an E8-119. Who cares if you fill it up to the rated pressure.. everyone can fill over 2640 psi.

 

[jumbo]

Lp tanks-

Easy to fill on any compressor , that would be the best advantage that I could think of. I have heard Lp is easier on gear but I dont know how much validity there is to that statement.

jumbo

 

[Creed]

Since HP tanks are now readily available from most manufacturers, and affordable - why are people still buying LP tanks instead?

just curious.

A lot of vintage equipment(think Aquamasters and the like) were designed around 1800 and 2250 psi tanks. The hp seats tend to live longer under the lesser pressures. Or so I've read. Personally, I like it when people buy new tanks, and sell me their old steel 72's and whatnot for a pittance.

 

[lamont]

HP tanks can be just as easy on compressors if you fill them to 2640 psi instead of 3500 psi.

E8-130 @ 2640 = LP104
E8-119 @ 2640 = LP95
E7-120 @ 2640 = LP96
E7-100 @ 2640 = LP80

Similarly, you lose nothing with a 3200 psi short/hot fill in an HP tank when you compare it to the LP tank with the equivalent water volume (and weight budget on your back).

There are minor differences in trim and buoyancy between the LP and HP versions of the same water volume tank. If you aren't a tank connaisseur, though, the only reasons to prefer an LP tank over an HP tank are price and availability.

(oh yeah, and the LP120/125s are 150+ cu ft when you jack them up to 3500+ psi and can't be beat...)

 

[Blitz]

LP, for mostly the same reasons that everyone else has mentioned. I do like that my dual HP100s require me to wear no additional weight, though.

 

[Leadking]

The impression of the diving public toward overfilling steel cylinders with the thought that is acceptable is confusing to me. If filling a steel to hydro pressure is considered reasonable, why not fill an aluminum 3000 psi cylinder to 5000 psi and get 52 more CF?

What is the reasoning? Both cylinder designs have been tested to a minimum of 10,000 hydro cycles without fail for DOT approval. How does the diving public rationalize this?

I just want the rationalization not a war!

 

[oxyhacker]

Because (if I may play devil's advocate) the secret to overfilling is not just to overfill grossly and randomly, but to do it intelligently The current overfill limits common in cave country were not arrived at randomly, but incrementally over time, with a lot of ad hoc experimentation, and a bit of engineering analysis on the side. And it was found that it worked for LP steels, but not for alu. Both may pass the same tests in the certification stage, but the question you have to ask is, by how much margin?

The safety record that steel tanks, even with overfilling, have accrued show that the overfillers were quite right in their conclusions.

I would agree that it doesn't make a lot of sense to buy old-style LPs with the intention of overfilling, now that almost identical tanks are available rated for the higher pressure. Or at least, won't once the supply and price issues level off. However, it is worth pointing out that the HP PSTs have had hydro issues, and that the Worthingtons have yet to develop a track record, so one (playing devil's advocate again) might still argue that the LPs are a safer bet.

The impression of the diving public toward overfilling steel cylinders with the thought that is acceptable is confusing to me. If filling a steel to hydro pressure is considered reasonable, why not fill an aluminum 3000 psi cylinder to 5000 psi and get 52 more CF?

What is the reasoning? Both cylinder designs have been tested to a minimum of 10,000 hydro cycles without fail for DOT approval. How does the diving public rationalize this?

I just want the rationalization not a war!