LP vs HP question

[SparticleBrane]

Nick I hope you're being sarcastic.

 

[limeyx]

Nick I hope you're being sarcastic.

Me ? never. My tank goes to 11 -- look!
I definitely prefer a "full" tank to an only 90% full one, and with HP I just cannot get the full fills I desire!

 

[Teamcasa]

Yah, exactly. Everyone knows LP is way easier to fill with partial pressure than HP.
besides, I can get a "full" fill in my LP -- if I get an HP, since the boats only fill to 3000 psi hot, I will never have a full fill.

I don't know how a LP is easier to fill but I do know that our local (SoCal) boats rarely fill past 3000.

 

[DA Aquamaster]

What does this mean? Wouldn't the pressure be the same when each tank filled to the same pressure? For a LP95 and HP119? Just more CF for the HP119.

Exactly.

The point here is that if tank 1 is low pressure and has volume X at its service pressure (plus 10%) of 2640psi and volume Y at a 3500 psi overfill. And tank 2 is high presure and has volume X when underfilled to 2640 psi and has volume Y when filled to its service pressure of 3500 psi, and both tanks 1 and 2 are basically the same size and weight, it makes no difference in terms of partial pressure blending.

You have what you have for O2 and for a givne pressure in the O2 tank you transfill from you will get the same end pressure and percentage of nitrox in either tank 1 or tank 2.

Now, personally, I am going to be using all of the O2 in the tank mixing with a nitrox stick and will still get a full HP tank anyway since I can use all the o2 in the supply bottle. Partial pressure blending is so 20th century.

 

[dannobee]

... Partial pressure blending is so 20th century.

I thought you were still PP blending He, or are you running in through the stick now too?

 

[DA Aquamaster]

Two sticks in series with two O2 analyzers and you can do trimix without partial blending or even an He analyzer. No left over O2 or He in tanks that would otherwise require a booster.

 

[CompuDude]

I don't know how a LP is easier to fill but I do know that our local (SoCal) boats rarely fill past 3000.

I'd have to say that really depends on which boats you're diving.

I get good HP fills on both the Peace and the Sea Bass, the two SoCal boats I dive most often.

 

[CompuDude]

Get the best tank for your needs. The new HP tanks come with Pro Valve for both Yoke and DIN connection. Some shops charge more for a HP fill. The new tanks are O2 cleaned and Nitrox ready. Also check the buoyancy characteristics and empty weight. I do not want to have more weight on my belt or be lugging a huge tank around when shore diving and hiking down cliffs. If I can have a slightly negative buoyancy when empty tank is best for me vs a slightly positive.

What local shops are you hitting that charge extra for HP fills? I've heard of this before, but mostly in flyover country. I've never heard of L.A.-area shops doing this... but if there is one out there, I'd like to know so I can avoid them like the plague they are.

 

[cmburch]

What local shops are you hitting that charge extra for HP fills? I've heard of this before, but mostly in flyover country. I've never heard of L.A.-area shops doing this... but if there is one out there, I'd like to know so I can avoid them like the plague they are.

I have just noticed this. I think it may be shops further from the water, Concord. Some of my favorite shops Wet Pleasure, Santa Clara and Any Water, San Jose almost give away the fills with good deals on fill cards and incentives, etc. It may be an advertising thing to get you into the store.

There is a Dive Rite shop in Pittsburgh the charges by the partial fill. I might not have this right. I you come in with a 2/3 full tank you are only charged for the additional third? I'll have to read the website again.

 

[CompuDude]

I have just noticed this. I think it may be shops further from the water, Concord. Some of my favorite shops Wet Pleasure, Santa Clara and Any Water, San Jose almost give away the fills with good deals on fill cards and incentives, etc. It may be an advertising thing to get you into the store.

There is a Dive Rite shop in Pittsburgh the charges by the partial fill. I might not have this right. I you come in with a 2/3 full tank you are only charged for the additional third? I'll have to read the website again.

Ah, ok... that's right, you're NoCal. Mental Note: Diving up North, fill up close to the ocean.

Fill Express in Florida sells by the cf... I sure wish we had some of those around here! More useful when you're diving thirds (or sixths) in the caves than here, though, where on occasion I'll suck my tanks WAY lower than the recommended 500 psi on shore dives when I'm in 20' of water and there's not much surf to get through...