Welding grade O2 (again)

decoweenie · 9th November 2006, 13:00

Quote: (Originally Posted by jaap)

I would imagine that vaccuming an empty cylinder would be difficult with that sort of thing on it?

Why ?

Vacuuming a cylinder is essentially creating a delta-P with the low pressure side on the outside - which is same as full cylinder.

***EBT*** · 9th November 2006, 13:03

Because someone called it a one way valve (below certain pressures).

The Purist · 9th November 2006, 13:12

Quote: (Originally Posted by Ben Field)

I live in Essex, I keep hearing that there is a supplier who will lend you the J's rental free.. can I find them/will someone tell me? NO, because I only want one and I'll have it for months and months.

Try

Lakeside Diving.com

decoweenie · 9th November 2006, 13:40

Quote: (Originally Posted by EBT)

Because someone called it a one way valve (below certain pressures).

OK, I didn't read everything... That line just caught my eye as I scanned the posts...

jaap · 9th November 2006, 13:42

Quote: (Originally Posted by decoweenie)

Why ?

Vacuuming a cylinder is essentially creating a delta-P with the low pressure side on the outside - which is same as full cylinder.

If it true that the "spring thing" works in such a way that it closes when there is ~+0.5 barg over the valve relative to the outside. Then how do you expect to get the pressure in the cylinder to less than ~0.5 bar by applying a vaccum to the outside of the valve? That is unless you somehow bypassed the "spring thing" or invented some kind of device capable of producing a vaccum that is a negative pressure ;-)

Also its not clear if this "spring thing" closes at ~0.5 barg absolut or if its maybe even ~2.5 barg absolut? Depending on if we talk pressure gradient realtivt to ambient (~1bar) or absolut (0 bar).

lizardland · 9th November 2006, 13:42

Quote: (Originally Posted by decoweenie)

Why ?

Vacuuming a cylinder is essentially creating a delta-P with the low pressure side on the outside - which is same as full cylinder.

Don't you mean low pressure on the inside?

They pull the valve anyway before evacuating... Pretty much how I like to start my day as well

I've used welding grade in the past on the basis that I know a lot of steelwork fabricators but don't know many that have recently been blown up.

jaap · 9th November 2006, 14:04

Quote: (Originally Posted by lizardland)

Don't you mean low pressure on the inside?

They pull the valve anyway before evacuating... Pretty much how I like to start my day as well

I've used welding grade in the past on the basis that I know a lot of steelwork fabricators but don't know many that have recently been blown up.

Pull the valve? Do you say that the valve is removed prior to every evacuation? I really have a hard time seeing why they would do that.
Its really alot more work and would intoduce more problems like missfitted valves driving the cost up.

As I get it the cheapest gassses are not always evacuated by all companies before refilling. The slightly more expensive qualities are usually evacuated, sometimes even several times and also flushed. But the valve stays on. The very expensive qualities are ofcourse also evacuated and so on but the content of the individual cylinders are also analyzed making them alot more expensive.

AFAIK valves are usually only removed if there is a suspicion of contamination or at annual inspections. Some cylinders are not even inspected more than every 10 years at the hydro.

The above is what I have learned from talking to representatives and friends that work for the major gas suppliers in Sweden, so I have no clue how valid it is for other countries.

lizardland · 9th November 2006, 15:13

They don't pull a vacuum on cheaper grade gases.

Scubascooby · 9th November 2006, 15:33

Just a suggestion, maybe the filling whip has a different end to the normal decanting whip, allowing it to open any internal, spring-loaded, one-way, anti-numpty mechanism

jaap · 9th November 2006, 16:01

Quote: (Originally Posted by Scubascooby)

Just a suggestion, maybe the filling whip has a different end to the normal decanting whip, allowing it to open any internal, spring-loaded, one-way, anti-numpty mechanism

Yes I know they sometimes have that on cylinders. And I know it can be bypassed by fitting the right kind of adapter (I have done it). Ofcourse that sort of a thing would be bypassed by the proper fill gear to allow for filling/vacuming.

9th November 2006, 13:00	#31 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Welding grade O2 (again) Quote: (Originally Posted by jaap) I would imagine that vaccuming an empty cylinder would be difficult with that sort of thing on it? Why ? Vacuuming a cylinder is essentially creating a delta-P with the low pressure side on the outside - which is same as full cylinder. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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9th November 2006, 13:03	#32 (permalink)
*EBT* Apprentice Luddite Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: UK, Brighton Posts: 2,111	Re: Welding grade O2 (again) Because someone called it a one way valve (below certain pressures). __________________ Eagles May Soar, but weasels don't get sucked into jet engines! RBW Terms of service
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9th November 2006, 13:12	#33 (permalink)
The Purist RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Jun 2005 Location: UK Posts: 102	Re: Welding grade O2 (again) Quote: (Originally Posted by Ben Field) I live in Essex, I keep hearing that there is a supplier who will lend you the J's rental free.. can I find them/will someone tell me? NO, because I only want one and I'll have it for months and months. Try Lakeside Diving.com
(Offline)

9th November 2006, 13:40	#34 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Welding grade O2 (again) Quote: (Originally Posted by EBT) Because someone called it a one way valve (below certain pressures). OK, I didn't read everything... That line just caught my eye as I scanned the posts... __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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9th November 2006, 13:42	#35 (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: 473	Re: Welding grade O2 (again) Quote: (Originally Posted by decoweenie) Why ? Vacuuming a cylinder is essentially creating a delta-P with the low pressure side on the outside - which is same as full cylinder. If it true that the "spring thing" works in such a way that it closes when there is ~+0.5 barg over the valve relative to the outside. Then how do you expect to get the pressure in the cylinder to less than ~0.5 bar by applying a vaccum to the outside of the valve? That is unless you somehow bypassed the "spring thing" or invented some kind of device capable of producing a vaccum that is a negative pressure ;-) Also its not clear if this "spring thing" closes at ~0.5 barg absolut or if its maybe even ~2.5 barg absolut? Depending on if we talk pressure gradient realtivt to ambient (~1bar) or absolut (0 bar). __________________ My initials: JAAP
(Online)

9th November 2006, 13:42	#36 (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: 1,387	Re: Welding grade O2 (again) Quote: (Originally Posted by decoweenie) Why ? Vacuuming a cylinder is essentially creating a delta-P with the low pressure side on the outside - which is same as full cylinder. Don't you mean low pressure on the inside? They pull the valve anyway before evacuating... Pretty much how I like to start my day as well I've used welding grade in the past on the basis that I know a lot of steelwork fabricators but don't know many that have recently been blown up. __________________ 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)

9th November 2006, 14:04	#37 (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: 473	Re: Welding grade O2 (again) Quote: (Originally Posted by lizardland) Don't you mean low pressure on the inside? They pull the valve anyway before evacuating... Pretty much how I like to start my day as well I've used welding grade in the past on the basis that I know a lot of steelwork fabricators but don't know many that have recently been blown up. Pull the valve? Do you say that the valve is removed prior to every evacuation? I really have a hard time seeing why they would do that. Its really alot more work and would intoduce more problems like missfitted valves driving the cost up. As I get it the cheapest gassses are not always evacuated by all companies before refilling. The slightly more expensive qualities are usually evacuated, sometimes even several times and also flushed. But the valve stays on. The very expensive qualities are ofcourse also evacuated and so on but the content of the individual cylinders are also analyzed making them alot more expensive. AFAIK valves are usually only removed if there is a suspicion of contamination or at annual inspections. Some cylinders are not even inspected more than every 10 years at the hydro. The above is what I have learned from talking to representatives and friends that work for the major gas suppliers in Sweden, so I have no clue how valid it is for other countries. __________________ My initials: JAAP
(Online)

9th November 2006, 15:13	#38 (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: 1,387	Re: Welding grade O2 (again) They don't pull a vacuum on cheaper grade gases. __________________ 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)

9th November 2006, 15:33	#39 (permalink)
Scubascooby Better Off Out of the EU Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Nov 2005 Location: Great Britain Posts: 418	Re: Welding grade O2 (again) Just a suggestion, maybe the filling whip has a different end to the normal decanting whip, allowing it to open any internal, spring-loaded, one-way, anti-numpty mechanism __________________ "dove" is NOT the past tense of "dive" Better off OUT of the EU ! www.hugsac.org.uk
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9th November 2006, 16:01	#40 (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: 473	Re: Welding grade O2 (again) Quote: (Originally Posted by Scubascooby) Just a suggestion, maybe the filling whip has a different end to the normal decanting whip, allowing it to open any internal, spring-loaded, one-way, anti-numpty mechanism Yes I know they sometimes have that on cylinders. And I know it can be bypassed by fitting the right kind of adapter (I have done it). Ofcourse that sort of a thing would be bypassed by the proper fill gear to allow for filling/vacuming. __________________ My initials: JAAP
(Online)

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