My first Tanks

mag3 wrote:
> Question being, for a steel 120 rated at 230bar/3442 PSI, is there any margin for "overfilling"

Of course. Misunderstood in general, pressure ratings are in psig at
20C. This *automatically* translates to higher pressures at higher
temperatures. The cylinder specification incorporates all this. DOT
cylinder specifications are for industry and transport, not for scuba.
As such, they are overbuilt by orders of magnitude. They are expected
to be stored in steel mills and left baking in Death Valley sun for
months on end. They're also expected to be run over by trucks, dropped
from buildings and slammed into bridge abutments at high speeds. The
3AA cylinder standard has been unblemished since the 40's.

My fill station always fills these to 4200 psig, which cools to about
35-3700 depending on how fast they filled them. The faster they fill
them, the hotter they get, and the more they drop. It really doesn't
make much difference. Other shops here routinely fill for 4000 psig
(cool).

Knowledgeable shops aren't very concerned about steel tanks in good
condition.
1) they can't hurt them with shop compressors
2) even if they could, steel wouldn't have the drama of aluminum when
it fails

> and what would be the max to which it could be filled without any danger to the tank or the
> 1st stage (which in the case of my 2 regs, are rated to 3500PSI each as well)?

Your shop doesn't have a powerful enough compressor to hurt your steel
tanks.

> 2nd Question - The LDS recommended converting the regs to DIN for these tanks but I hear from
> other shops that it is not necessary. Thoughts?

I wouldn't do it, unless you like to fiddle fart around with
crossthreads and 90 sizes/styles of o-ring. I've had mine(A-clamp) at
4000 psig without incident, but I don't make it a habit and that was
not on purpose. Your cylinders came with the new valves right (they
have removable inserts)?

Some people just like DIN. They like to screw things. It gives them a
woodie.

I *way* prefer A-clamp to DIN. I travel dive a lot, and wouldn't want
the adapter shoving the thing into the back of my head on the
inevitable AL80s. Diving locally, I swap tanks in half the time it
takes DIN guys. That counts for something when the seas a running big.
I own native DIN assemblies for my regs, but haven't used them in
years...In steel tanks, I think yoke is also less apt to get water in
the tank. It sure as hell has less to blow out.

Then there's all that fun when some prankster opens your valve with the
dust caps in...

300 Bar is a *really* big fill (4350psig). I guess if that's what you
dived with all the time, then DIN would probably be the way to go. I
only know one company that makes that tank (Luxfer) and I've only seen
two of them. Who wants glass wrapped Aluminum?

If you decide to convert, make sure you convert to 300 bar DIN, not 200
Bar DIN. SP has both possibilities (or at least they used to). The
difference is the length of the post. If you rent DIN tanks somewhere,
they will likely be 300 bar DIN valves, and it's a real drag to find
your post is too short to fill the hole. About a year ago we had a guy
on the boat in that predicament, and the dive monkey tried to fix
things with a pair of channel locks....it wasn't pretty

bullshark

mag3 wrote:
> Question being, for a steel 120 rated at 230bar/3442 PSI, is there any margin for "overfilling"

Of course. Misunderstood in general, pressure ratings are in psig at
20C. This *automatically* translates to higher pressures at higher
temperatures. The cylinder specification incorporates all this. DOT
cylinder specifications are for industry and transport, not for scuba.
As such, they are overbuilt by orders of magnitude. They are expected
to be stored in steel mills and left baking in Death Valley sun for
months on end. They're also expected to be run over by trucks, dropped
from buildings and slammed into bridge abutments at high speeds. The
3AA cylinder standard has been unblemished since the 40's.

My fill station always fills these to 4200 psig, which cools to about
35-3700 depending on how fast they filled them. The faster they fill
them, the hotter they get, and the more they drop. It really doesn't
make much difference. Other shops here routinely fill for 4000 psig
(cool).

Knowledgeable shops aren't very concerned about steel tanks in good
condition.
1) they can't hurt them with shop compressors
2) even if they could, steel wouldn't have the drama of aluminum when
it fails

> and what would be the max to which it could be filled without any danger to the tank or the
> 1st stage (which in the case of my 2 regs, are rated to 3500PSI each as well)?

Your shop doesn't have a powerful enough compressor to hurt your steel
tanks.

> 2nd Question - The LDS recommended converting the regs to DIN for these tanks but I hear from
> other shops that it is not necessary. Thoughts?

I wouldn't do it, unless you like to fiddle fart around with
crossthreads and 90 sizes/styles of o-ring. I've had mine(A-clamp) at
4000 psig without incident, but I don't make it a habit and that was
not on purpose. Your cylinders came with the new valves right (they
have removable inserts)?

Some people just like DIN. They like to screw things. It gives them a
woodie.

I *way* prefer A-clamp to DIN. I travel dive a lot, and wouldn't want
the adapter shoving the thing into the back of my head on the
inevitable AL80s. Diving locally, I swap tanks in half the time it
takes DIN guys. That counts for something when the seas a running big.
I own native DIN assemblies for my regs, but haven't used them in
years...In steel tanks, I think yoke is also less apt to get water in
the tank. It sure as hell has less to blow out.

Then there's all that fun when some prankster opens your valve with the
dust caps in...

300 Bar is a *really* big fill (4350psig). I guess if that's what you
dived with all the time, then DIN would probably be the way to go. I
only know one company that makes that tank (Luxfer) and I've only seen
two of them. Who wants glass wrapped Aluminum?

If you decide to convert, make sure you convert to 300 bar DIN, not 200
Bar DIN. SP has both possibilities (or at least they used to). The
difference is the length of the post. If you rent DIN tanks somewhere,
they will likely be 300 bar DIN valves, and it's a real drag to find
your post is too short to fill the hole. About a year ago we had a guy
on the boat in that predicament, and the dive monkey tried to fix
things with a pair of channel locks....it wasn't pretty

bullshark

In article <12ccio3rb955o00@news.supernews.com>, none@none.invalid
says...

> Ouch! Kinda harsh, Al.
Perhaps a bit, but I got really spoiled in FL and SC. There are, of
couse, plenty of idiots there too. I am willing to belive that there may
be a good shop here. but I haven't seen it yet.

> I've trained the local guy, he's a smidge better. Not exactly DIR, though.
> But most of the time, I know what's BS and what is not. I was forced to learn.
> I don't have my own fill station, and I do buy parts at the LDS form time to
> time.

The best shops I know are not DIR, but they just do exactly what you
ask, tell really funny stories while you're waiting, and charge a fair
price.

> > If I do decide to start diving here, I'll buy a compressor and dive from my
> > brother's boat.
>
> Need a buddy?

I'm not planning on anything right now, but if I do, I'll be in touch.

In article <12ccio3rb955o00@news.supernews.com>, none@none.invalid
says...

> Ouch! Kinda harsh, Al.
Perhaps a bit, but I got really spoiled in FL and SC. There are, of
couse, plenty of idiots there too. I am willing to belive that there may
be a good shop here. but I haven't seen it yet.

> I've trained the local guy, he's a smidge better. Not exactly DIR, though.
> But most of the time, I know what's BS and what is not. I was forced to learn.
> I don't have my own fill station, and I do buy parts at the LDS form time to
> time.

The best shops I know are not DIR, but they just do exactly what you
ask, tell really funny stories while you're waiting, and charge a fair
price.

> > If I do decide to start diving here, I'll buy a compressor and dive from my
> > brother's boat.
>
> Need a buddy?

I'm not planning on anything right now, but if I do, I'll be in touch.

mag3 wrote:
> On 25 Jul 2006 08:38:17 -0700, "Al Wells" <al.wells@gmail.com> wrote:
>
> Well, they have a hut so it's not directly in the sun, but they have no water bath
> at all, and it was a fast fill (I'd say no more than 10 minutes).

You don't want a water bath. Ever. That's stroke stuff. It doesn't do
anything except increase risk of getting water in your tanks. Heat
within reason is just fine. This isn't the 60's anymore. The O-rings
and lubricants in your valves aren't adversely affected by a little
heat. It certainly won't affect the tank unless you get it up to
temperatures that affect temper, and I don't think that's happening.

10 minutes isn't all that fast (400 psi/min). They would be hot, but
that's OK. Tanks always get hot when you fill them, and as long as it
doesn't fry bacon, it's not a big deal. My steels, which get filled at
least once a week (x4), are routinely too hot to lay my hand on
comfortably and keep it there for long.

If it really took 10 minutes. they should have been fine, 33-34 at the
worst. Maybe your valves weren't shut tight. Next time you fill, squirt
a little water on the burst discs to see if they bubble. They might not
be tight. After all, they *are* new.

Sometimes people roll the valves open (just a little) when they carry
them. Point the valve handle forward in the right hand, and aft in the
left. That way they can only roll more tightly closed.

bullshark

The tanks were scorching
> hot when I got them. I should have checked the pressure then but I was wanting to get home.
> The ambient temp outside during the fill was low 80's as well. After 2 days in my air conditioned
> basement (70F) they were down to between 3000 - 3100 PSI. Maybe they'll perk up a bit when
> I get them back outside again.

mag3 wrote:
> On 25 Jul 2006 08:38:17 -0700, "Al Wells" <al.wells@gmail.com> wrote:
>
> Well, they have a hut so it's not directly in the sun, but they have no water bath
> at all, and it was a fast fill (I'd say no more than 10 minutes).

You don't want a water bath. Ever. That's stroke stuff. It doesn't do
anything except increase risk of getting water in your tanks. Heat
within reason is just fine. This isn't the 60's anymore. The O-rings
and lubricants in your valves aren't adversely affected by a little
heat. It certainly won't affect the tank unless you get it up to
temperatures that affect temper, and I don't think that's happening.

10 minutes isn't all that fast (400 psi/min). They would be hot, but
that's OK. Tanks always get hot when you fill them, and as long as it
doesn't fry bacon, it's not a big deal. My steels, which get filled at
least once a week (x4), are routinely too hot to lay my hand on
comfortably and keep it there for long.

If it really took 10 minutes. they should have been fine, 33-34 at the
worst. Maybe your valves weren't shut tight. Next time you fill, squirt
a little water on the burst discs to see if they bubble. They might not
be tight. After all, they *are* new.

Sometimes people roll the valves open (just a little) when they carry
them. Point the valve handle forward in the right hand, and aft in the
left. That way they can only roll more tightly closed.

bullshark

The tanks were scorching
> hot when I got them. I should have checked the pressure then but I was wanting to get home.
> The ambient temp outside during the fill was low 80's as well. After 2 days in my air conditioned
> basement (70F) they were down to between 3000 - 3100 PSI. Maybe they'll perk up a bit when
> I get them back outside again.

bullshark wrote

> That's stroke stuff.

Your scaring me.

bullshark wrote

> That's stroke stuff.

Your scaring me.

On Wed, 26 Jul 2006 07:55:08 -0400, Lee Bell wrote:
> bullshark wrote
>
> > That's stroke stuff.
>
> Your scaring me.

Me too!

--
Art Greenberg
artg at eclipse dot net

On Wed, 26 Jul 2006 07:55:08 -0400, Lee Bell wrote:
> bullshark wrote
>
> > That's stroke stuff.
>
> Your scaring me.

Me too!

--
Art Greenberg
artg at eclipse dot net