Hand pumps or Dive bottles?

[zanes]

No. What would happen?

I suspect it's a case of "look, dive bottles which I think were filled from a decent compressor get rusty too!!!!1111!!11"

What this misses, of course, is that the only dive bottles that get condemned during testing (either from the visual inspection or the pressure test) get cut up. And there's no knowing what abuse they've taken (run empty, filled from dodgy third world compressors, had a sub-surface life etc.)

Many, many cylinders live exceptionally long lives- case in point, we had two very old (30 year+) BA cylinders that only failed test because they'd been stamped on the neck (a failure in the case of thin walled BA cylinders). And they were a bit shite for what we wanted, being 200BAR.

The only fair test would be to get two steel PCP cylinders and fill and use both a set number of times, but no one will do that to two good cylinders!

Even if pumps gave out perfectly dry air (and in fairness I don't know that they don't) I still can't see why anyone would want to use one now 300BAR cylinders are so cheap.

[Greenfingers]

My take on the subject is anyone that uses a pump will tell you that they keep you fit and are not that hard to use.
Bottle users will tell you that pumps are water hazards and are very hard to use.
horses for courses lol.

[blooregard]

I suspect it's a case of "look, dive bottles which I think were filled from a decent compressor get rusty too!!!!1111!!11"

What this misses, of course, is that the only dive bottles that get condemned during testing (either from the visual inspection or the pressure test) get cut up. And there's no knowing what abuse they've taken (run empty, filled from dodgy third world compressors, had a sub-surface life etc.)

Many, many cylinders live exceptionally long lives- case in point, we had two very old (30 year+) BA cylinders that only failed test because they'd been stamped on the neck (a failure in the case of thin walled BA cylinders). And they were a bit shite for what we wanted, being 200BAR.

The only fair test would be to get two steel PCP cylinders and fill and use both a set number of times, but no one will do that to two good cylinders!

Even if pumps gave out perfectly dry air (and in fairness I don't know that they don't) I still can't see why anyone would want to use one now 300BAR cylinders are so cheap.

Fair points chap, but most of us never know how good a compressor is, and you never know the state of your bottle or what is inside it until it gets condemed.

I use both fililng methods myself (well I will be doing when I buy another pump) and I choose not to be concerned about moisture in my guns, it's never been a problem and I doubt it ever will be. I just like the fact that from a pump you are never going to be let down by a lack fo air supply.

[RobF]

I

Even if pumps gave out perfectly dry air (and in fairness I don't know that they don't) I still can't see why anyone would want to use one now 300BAR cylinders are so cheap.

Compressors don't compress perfectly dry air either. The air is for breathing and if you do use dry air it can irritate the throat lining.

But yes, for ease and cost a cylinder isn't much more than a pump cost wise and a lot less effort.

[zanes]

Compressors don't compress perfectly dry air either. The air is for breathing and if you do use dry air it can irritate the throat lining.

Interesting point. I've now looked into this very briefly (not because I want to prove you wrong, but because it's intrigued me!).

EN12021 specifies <50mg/cubic metre water vapour for air at 200BAR. Air at 20 degrees with 50% RH (rather dry for the UK!) contains roughly 8.6g/cubic metre water vapour at atmospheric pressure (so straight compression would result in air with 8.6x200 = 1720g/m^3). Whilst you're quite correct that it isn't perfectly dry, it's certainly very dry relative to atmospheric air.

From HERE: http://www.scubaengineer.com/high_pr...or_filtrat.htm

To fill only one standard aluminum DOT-3AL3000 80cuft (207bar/11Liter) scuba cylinder with divers breathing quality air at 35 degrees ‘C’ ambient (leading to a final filter tower of typically 45 degrees ‘C’) will require the compressor condensate system to remove (11 x 207 x 65.5)/1000 = 149cc of water [note 1litre = 1x10^-3 cubic metres],
[...]
After compressing to 140bars and removal of 99.3% of all the water in the air, is the air now dry enough to pass EN12021 humidity standards? Answer: Sadly NOT. It isn’t even anywhere near the required dryness standard!

Will a pump be anywhere near this?

But yes, for ease and cost a cylinder isn't much more than a pump cost wise and a lot less effort.

Agreed. An FX 3 Stage pump from Uttings is £138.99. The same price as a 4 litre 300BAR cylinder from Go Dive.

[harvey_s]

An FX 3 Stage pump from Uttings is £138.99. The same price as a 4 litre 300BAR cylinder from Go Dive.

Unfortunately though... this, unlike your local coffee emporium, does not come with either free refills or a free mandatory inspection/test every X years.

I wonder how we all got on before Scuba sets got invented....see below gents and feast your eyes on the joy of pumping
http://www.network54.com/Forum/68145...+Dean+Fletcher