PST LP80's Fill Pressure

[storms]

I recently purchased three PST LP 80's from a local LDS. I have a few questions on fill pressure's. I know the suggested psi is 2400 with a 10% overfill of 2640 @ 80 cubic feet of air. I have heard of some people overfill these tanks to well above 3200psi.
First question: What is the ruputure disc on the factory valve rated at? Second question: What pressure is there 100 cubic feet of air in a LP80? If there is already a thread on this discussion just point me in the right direct, a search yielded nothing on the subject.

 

[scubasean]

I am quite uncomfortable with overfilling tanks beyond rated capacity (I consider the 10% overfill to be within rated capacity).

Fooling around with compressed air like that seems like a recipe for an accident.

But I'm not an expert by any means.

 

[Genesis]

The burst disc SHOULD be rated at the hydro test pressure, with a spec of plus 0, minus 10%. HOWEVER, that assumes the valve and tank are "matched" - they often aren't, as people swap valves and some shops buy tanks WITHOUT valves attached.

So any "rational" overfill should be ok from THAT perspective.

I don't know about the general wisdom of overfilling tanks by the kind of gross amount that is often done in "cave country." I won't do it with my compressor, but then again its my tush if the tank blows up when I'm filling a tank while standing next to it!

 

[chrpai]

[QUOTE
First question: What is the ruputure disc on the factory valve rated at?
[/QUOTE]

Previously covered.

Second question: What pressure is there 100 cubic feet of air in a LP80?
]

100cf is 125% of 80cf. Since an LP80 is rated at 80cf at a 10% + pressure ( 2640psi ) then at 3300PSI it will contain 100cf of gas.

The "cave fill" you describe is most often done with an LP104. These are rated 104cf at 2640 (+) and between 3300 - 3500 PSI they contain 130 - 140cf of gas.

Other then the problems associated with real vs ideal gas laws at higher psi, and having a regulator with a hp seat that can handle the PSI ( read DIN ) I don't have any problems with overfilling steel tanks.

Whats the joke?

Q: How often do you Hydro your tanks?
A: Every time I fill them.

 

[chrpai]

Genesis once bubbled...

I don't know about the general wisdom of overfilling tanks by the kind of gross amount that is often done in "cave country." I won't do it with my compressor, but then again its my tush if the tank blows up when I'm filling a tank while standing next to it!

www.fillexpress.com has some pretty good policies. One of is:

"Fill Express does not overfill any aluminum cylinder. Overfilling shortens cylinder life, as well as increases risk of cylinder failure. Increased pressures also can cause burst disks, O-rings, and 1st stage regulator seats to unexpectedly fail prematurely. Willing to accept these risks in exchange for the increased gas volume, technical divers sometimes overfill their meticulously maintained steel cylinders. Upon request, Fill Express overfills those privately owned modern chrome molybdenum steel cylinders that we find to be in excellent condition. We will fill a low-pressure (2640 psi) cylinder up to 3000 psi if it has a yoke valve and up to 3500 psi if it has a DIN valve. We will fill a high-pressure (3500 psi) cylinder with a 300-Bar DIN valve up to 4000 psi. Fill Express may refuse to overfill a cylinder for any reason; the final decision rests solely upon the fill station operator."

 

[Dryglove]

scubasean once bubbled...
I am quite uncomfortable with overfilling tanks beyond rated capacity (I consider the 10% overfill to be within rated capacity).

You dont have to worry about overfills in CA as hardly any one will do it.And if they do, they consider 100-200lbs an overfill which cools to the specified pressure anyways. I have a hard enough time not getting a short fill sometimes and i dive LP tanks

I hear its common to get overfills in places like florida. Read this
http://www.fillexpress.com/library/fillfaq.shtml#procedures and pay attention to this section

"Upon request, Fill Express overfills those privately owned modern chrome molybdenum steel cylinders that we find to be in excellent condition. We will fill a low-pressure (2640 psi) cylinder up to 3000 psi if it has a yoke valve and up to 3500 psi if it has a DIN valve. We will fill a high-pressure (3500 psi) cylinder with a 300-Bar DIN valve up to 4000 psi. Fill Express may refuse to overfill a cylinder for any reason; the final decision rests solely upon the fill station operator."

 

[Dryglove]

chrpai once bubbled...


www.fillexpress.com has some pretty good policies. One of is:

"Fill Express does not overfill any aluminum cylinder. Overfilling shortens cylinder life, as well as increases risk of cylinder failure. Increased pressures also can cause burst disks, O-rings, and 1st stage regulator seats to unexpectedly fail prematurely. Willing to accept these risks in exchange for the increased gas volume, technical divers sometimes overfill their meticulously maintained steel cylinders. Upon request, Fill Express overfills those privately owned modern chrome molybdenum steel cylinders that we find to be in excellent condition. We will fill a low-pressure (2640 psi) cylinder up to 3000 psi if it has a yoke valve and up to 3500 psi if it has a DIN valve. We will fill a high-pressure (3500 psi) cylinder with a 300-Bar DIN valve up to 4000 psi. Fill Express may refuse to overfill a cylinder for any reason; the final decision rests solely upon the fill station operator."

Darn you beat me to it by 4 min, it sucks being a slow typer

 

[Genesis]

I'm aware of their policy, but my personal one, with my fill station, is that I don't do it - steel or otherwise.

If someone else wants to, that's their biz - so long as I'm not standing next to the cylinder while they do it

 

[Northeastwrecks]

lal7176 once bubbled...
"Upon request, Fill Express overfills those privately owned modern chrome molybdenum steel cylinders that we find to be in excellent condition. We will fill a low-pressure (2640 psi) cylinder up to 3000 psi if it has a yoke valve and up to 3500 psi if it has a DIN valve. We will fill a high-pressure (3500 psi) cylinder with a 300-Bar DIN valve up to 4000 psi. Fill Express may refuse to overfill a cylinder for any reason; the final decision rests solely upon the fill station operator."

My dive buddies and I will jack our 104's (meticulously maintained, of course, LOL) to 3000 - 3300 depending on our gas requirements. Its not uncommon in the wreck community up here, just like it appears to be fairly common in the cave community in Florida.

Of course, we are also filling our own tanks. I don't ask the regular fill guys to do that.

I can't believe that they put this in writing.

 

[scubasean]

lal7176 once bubbled...


You dont have to worry about overfills in CA as hardly any one will do it.And if they do, they consider 100-200lbs an overfill which cools to the specified pressure anyways. I have a hard enough time not getting a short fill sometimes and i dive LP tanks

I hear its common to get overfills in places like florida.

Interesting...I learn something new every day...

One of my issues is that my first stage (an Oceanic CDX5) says "3500 PSI" on it. I presume that means that I should not use it on a tank having a greater pressure than 3500 PSI....Since my HP 100 is rated to 3450 or so, this tells me that I don't want it overfilled...

Am I missing something? Is my first stage abnormal? Is the 3500 rating due to having a yoke valve?