max pressure in (stage) tanks

gallathan · 9th September 2007, 22:52

OK,I know I shouldn't do this / I have an appreciation of the risks, but just wondering if people have a fele for / regularly overpressurise their bailout stages. Why?, to avoid carying an extra tank and / or to allow for small losses over severl days of a trip where you take your own gasses etc. If so, what pressure do you fill your ali and steel tanks to? Answers in bar please...

***EBT*** · 10th September 2007, 00:32

Obviously not a recommendation. But.. steels are regularly seen overpressed to like 240+... alu... EEK! look athe materials data and you'll lose ANY desire to OP an alu tank.

Drmike · 10th September 2007, 05:43

Quote: (Originally Posted by EBT)

Obviously not a recommendation. But.. steels are regularly seen overpressed to like 240+... alu... EEK! look athe materials data and you'll lose ANY desire to OP an alu tank.

Bill R gave me a few 250bar O2 fills in NF few weeks back goto love cave divers and their fills

Personaly I have a rule: as soon as I start thinking I need to push up the tank pressures on bail gas to get the volumes needed I KNOW im cutting it too fine and need to take more tanks! Yes I do overfill (not much if AL) but I look at it as 'extra' gas ie its not counted in my bail out calcs.

Marc T · 10th September 2007, 07:23

An usual french cave divers joke is:dont exceed pressure test

But I regulary limit myself to 240-250 bar AND ONLY on steel tank and sometimes on some small and brand new ali tank ( and put them into a water container during inflation ).
For O2 Ill certainly nether play above 200 bar watether the metal of the tank.

Cheers

Marc

Ben Field · 10th September 2007, 08:27

I made the mistake of stipulating that the Steel 5ltr I left for filling was "emergancy" bailout and they very helpfully pumped it to 275bar...
(but then they do have a habit of using their O2 booster to its rated max pressure as well!!!!!!)

I once left an Ali Suitox bottle for filling at a famous UK inland dive site, it came back at 250bar and hot enough to cook bacon on!

Ekkk

Mark Chase · 10th September 2007, 09:05

I run my steel tanks at 250bar and my Ali80 at 235.

ATB

Mark Chase

jaap · 10th September 2007, 09:59

Quote: (Originally Posted by EBT)

Obviously not a recommendation. But.. steels are regularly seen overpressed to like 240+... alu... EEK! look athe materials data and you'll lose ANY desire to OP an alu tank.

Hi

Sure one cannot tell someone its fine to go beyond the legal working pressure.

Would you care to expand on the "loss of any desire..." ?
If you have any real life example from an alu cylinder failure due to OP by a user that would be very interesting (no 6351 pls)

Many newer alu cylinders have an additional thing stamped adding to the stamped fill pressures (200 or 232 bar, and the test pressure 300 or ~348 bar. The additional thing could be: 260 bar at 60° C.

I guess the 260/60° C could be interpreted in various ways...

jaap · 10th September 2007, 10:05

Quote: (Originally Posted by Marc T)

For O2 Ill certainly nether play above 200 bar watether the metal of the tank.

Marc

If I'm fairly certain the system is clean and the filling and operation of valves is slow I don't hesitate to fill O2 to higher pressures. Filled some O2 to 270 bar last week.

But those that slam O2-cylinders to near 200 bar so that you can fry eggs on them scare me.

wondersea · 10th September 2007, 10:13

Right, I notice 3 pressures on some AL:

Pw = 200 bar working pressure
PT / PH test pressure = 300 bar
PS = 246 bar / 60°C

Can we fill an AL at the PS ??

I don't know the difference between them as I use to have steel tank with either service pressure to fill and test pressure = 1.5 * PS

lizardland · 10th September 2007, 13:23

Quote: (Originally Posted by jaap)

Would you care to expand on the "loss of any desire..." ?
If you have any real life example from an alu cylinder failure due to OP by a user that would be very interesting (no 6351 pls)

Not in gas vessels but in a structural setting I would never specify aluminium for anything that is going to suffer from repeated flexing, bending, etc. For constant, static loads then it's fine, it's not a happy material in dynamic uses generally.

9th September 2007, 22:52	#1 (permalink)
gallathan New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Mar 2006 Location: Laleham, Middlesex, England, UK Posts: 43	max pressure in (stage) tanks OK,I know I shouldn't do this / I have an appreciation of the risks, but just wondering if people have a fele for / regularly overpressurise their bailout stages. Why?, to avoid carying an extra tank and / or to allow for small losses over severl days of a trip where you take your own gasses etc. If so, what pressure do you fill your ali and steel tanks to? Answers in bar please...
(Offline)

10th September 2007, 00:32	#2 (permalink)
*EBT* Apprentice Luddite Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: UK, Brighton Posts: 1,855	Re: max pressure in (stage) tanks Obviously not a recommendation. But.. steels are regularly seen overpressed to like 240+... alu... EEK! look athe materials data and you'll lose ANY desire to OP an alu tank. __________________ Eagles May Soar, but weasels don't get sucked into jet engines! Rebreather World Terms of service Real diving t-shirts for real divers
(Offline)

10th September 2007, 05:43	#3 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: max pressure in (stage) tanks Quote: (Originally Posted by EBT) Obviously not a recommendation. But.. steels are regularly seen overpressed to like 240+... alu... EEK! look athe materials data and you'll lose ANY desire to OP an alu tank. Bill R gave me a few 250bar O2 fills in NF few weeks back goto love cave divers and their fills Personaly I have a rule: as soon as I start thinking I need to push up the tank pressures on bail gas to get the volumes needed I KNOW im cutting it too fine and need to take more tanks! Yes I do overfill (not much if AL) but I look at it as 'extra' gas ie its not counted in my bail out calcs. __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you
(Offline)

10th September 2007, 07:23	#4 (permalink)
Marc T hell is in the details Current Rebreather/s: RB80 / Clone Home Build Other Rebreather/s: Not Bought Yet RB80 / Clone Home Build Join Date: Sep 2005 Location: FRANCE Carcassonne Posts: 440	Re: max pressure in (stage) tanks An usual french cave divers joke is:dont exceed pressure test But I regulary limit myself to 240-250 bar AND ONLY on steel tank and sometimes on some small and brand new ali tank ( and put them into a water container during inflation ). For O2 Ill certainly nether play above 200 bar watether the metal of the tank. Cheers Marc
(Offline)

10th September 2007, 08:27	#5 (permalink)
Ben Field CK+Shearwater Current Rebreather/s: Classic Kiss Other Rebreather/s: Sport Kiss Join Date: Aug 2005 Location: London, England Posts: 1,486	Re: max pressure in (stage) tanks I made the mistake of stipulating that the Steel 5ltr I left for filling was "emergancy" bailout and they very helpfully pumped it to 275bar... (but then they do have a habit of using their O2 booster to its rated max pressure as well!!!!!!) I once left an Ali Suitox bottle for filling at a famous UK inland dive site, it came back at 250bar and hot enough to cook bacon on! Ekkk __________________ www.hugsac.org.uk Beware Fridge Suck
(Offline)

10th September 2007, 09:05	#6 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,470	Re: max pressure in (stage) tanks I run my steel tanks at 250bar and my Ali80 at 235. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
(Offline)

10th September 2007, 09:59	#7 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 438	Re: max pressure in (stage) tanks Quote: (Originally Posted by EBT) Obviously not a recommendation. But.. steels are regularly seen overpressed to like 240+... alu... EEK! look athe materials data and you'll lose ANY desire to OP an alu tank. Hi Sure one cannot tell someone its fine to go beyond the legal working pressure. Would you care to expand on the "loss of any desire..." ? If you have any real life example from an alu cylinder failure due to OP by a user that would be very interesting (no 6351 pls) Many newer alu cylinders have an additional thing stamped adding to the stamped fill pressures (200 or 232 bar, and the test pressure 300 or ~348 bar. The additional thing could be: 260 bar at 60° C. I guess the 260/60° C could be interpreted in various ways... __________________ My initials: JAAP
(Offline)

10th September 2007, 10:05	#8 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 438	Re: max pressure in (stage) tanks Quote: (Originally Posted by Marc T) For O2 Ill certainly nether play above 200 bar watether the metal of the tank. Marc If I'm fairly certain the system is clean and the filling and operation of valves is slow I don't hesitate to fill O2 to higher pressures. Filled some O2 to 270 bar last week. But those that slam O2-cylinders to near 200 bar so that you can fry eggs on them scare me. __________________ My initials: JAAP
(Offline)

10th September 2007, 10:13	#9 (permalink)
wondersea New Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2006 Location: France - Gerzat (63) - Sanary (83) Posts: 76	Re: max pressure in (stage) tanks Right, I notice 3 pressures on some AL: Pw = 200 bar working pressure PT / PH test pressure = 300 bar PS = 246 bar / 60°C Can we fill an AL at the PS ?? I don't know the difference between them as I use to have steel tank with either service pressure to fill and test pressure = 1.5 * PS __________________ Antoine Pannetier DirRebreather member www.DIRRebreather.com
(Offline)

10th September 2007, 13:23	#10 (permalink)
lizardland Yak Current Rebreather/s: MK 15.X Home Build Other Rebreather/s: Classic Kiss Home Build Join Date: Mar 2005 Location: North... Posts: 1,189	Re: max pressure in (stage) tanks Quote: (Originally Posted by jaap) Would you care to expand on the "loss of any desire..." ? If you have any real life example from an alu cylinder failure due to OP by a user that would be very interesting (no 6351 pls) Not in gas vessels but in a structural setting I would never specify aluminium for anything that is going to suffer from repeated flexing, bending, etc. For constant, static loads then it's fine, it's not a happy material in dynamic uses generally. __________________ Can you imagine drifting along in the sea with your mouth open and a load of f***ing plankton going in? You'd like it, would you? www.westons-cider.co.uk Azerbaijani Association of Technical Divers Publicity Officer and Goat Wrangler
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode