Talk:Diving cylinder

	Underwater diving portal This article is part of WikiProject Underwater diving, an effort to create, expand, organize, and improve Underwater diving-related articles to a feature-quality standard, and to comprehensively cover the topic with quality encyclopedic articles.Underwater divingWikipedia:WikiProject Underwater divingTemplate:WikiProject Underwater divingUnderwater diving articles
Start	This article has been rated as Start-class on Wikipedia's content assessment scale.
???	This article has not yet received a rating on the importance scale.

Terminology

12/14/06 Discussion regarding the phrase copied below:

A diving cylinder (the term which tends to be used by divers) or SCUBA tank (more often used colloquially by non-divers)

As a NOWI Certified Diver and a PADI Certified Diver for more than twenty-five years, I can attest to the fact that I have never heard an American diver or American Oceanographer refer to our "Dive Tanks" as anything other than "Tanks." Therefore, the author's statment as prefaced above in parenthesis may be not be valid.

In any case, the reference to "non-divers" seems a bit unnecessary and sounds more like personal opinion rather than an actual fact. I recently, reviewed my old dive manuals whereby, the official terminology used here in the USA is "Tank" and not "Cylinder." The only exception I found was at a PADI web site tonight. However, I noticed the date of birth on the registration page of the website is European I.e. day/month/year as opposed to American month/day/year. Therefore,the term cylinder would be more appropriate coming from European divers. There is also a dive master video on the NOWI website regarding equipment. The term tank is being frequently used by the dive master when referring to the breathing unit.

European divers would generally refer to them as "tanks" - the proper name being a "cylinder" however, its not used in general speaking. Perhaps non-english speakers translate as cylinder? —Preceding unsigned comment added by 89.168.72.84 (talk) 23:05, 9 December 2007 (UTC)[reply]

I have seen the same (idiotic) argumnet over the term skeg or fin on a surfboard and have heard some say that only a non-surfer would say skeg. I simply believe this type of commentary detracts from the article in general and is therefore, may not necessary.

PEACE (LCrockett 04:16, 15 December 2006 (UTC))hope I did this correctly :-(?[reply]

You don't have to indent paragraphs (screws things up if you do). Otherwise you did fine.

I get three times as many Google hits on scuba tank as scuba cylinder. But I do notice that makers and engineers tend to call them cylinders. Perhaps this filters down to those who want to sound like the people who make (and service and hydrotest) the stuff, rather than just use it. S B H arris 08:23, 15 December 2006 (UTC)[reply]

Should Diving tank be added as a redirect to this article? --ArmadilloFromHellGateBridge 08:36, 15 December 2006 (UTC)[reply]

Yes, I think so, and have done so. Along the way I fixed the definitions so that I think everyone will be happy and satisfied. "Gas cylinder" is the generic term used by engineers and the ACGA people who use all kinds of sizes of compressed gas containers, not just the ones for scuba. Even the big H cylinders get called tanks by the non-cognoscenti, but never by people who work on them for a living. The same kind of distinction carries over to scuba. S B H arris 18:27, 15 December 2006 (UTC)[reply]

Diving Oxygen

"Breathing industrial compressed gases can be lethal because the high pressure increases the effect of any impurities in them.". I breath welding oxygen on a regular basis and so do a lot of other people. My research says it's the same oxygen used for both applications. Maybe that should be clarified. 142.165.246.187 16:13, 10 February 2007 (UTC)[reply]

I would wish to take issue that welding and breathing oxygen can be regarded as the same product. In the UK, USA and Europe there are both civilian and military specifications for welding oxygen and for diving quality oxygen (and medical oxygen). I would suggest that you could safely use diving oxygen and medical oxygen, if you wished, for welding but it would not be sensible to do so as these products are more expensive than welding oxygen. Likewise, you could use industrial grade oxygen (welding oxygen) for diving, however it is not sold (in the UK and Europe) as a breathing gas; and that it would be safer to use one that is sold for that purpose. Perhaps, that partially answers your point.Pyrotec 18:29, 10 February 2007 (UTC)[reply]

My anecdotal experience comes from talking to someone who worked for BOC (British Oxygen Company) some years ago. He maintained that all of the oxygen sold came from the same source, i.e. there was only one process used. The only exception being "Aviation grade" oxygen which had an extra stage of processing to remove any remaining water vapour because of the low temperatures that this oxygen may be exposed to. So medical, breathing and welding oxygen all came out of the same pipe. The catch was that BOC rented large cylinders to the end-user to hold the oxygen; when empty, these would simply be swapped for a full one. There was no procedure for ensuring that the cylinder was clean for customers who purchased welding oxygen, while the "higher" grades had the cylinders cleaned regularly. All of this seems to make commercial sense to me, so I have no reason to dispute his claims. Bottom line: you have a good chance of getting the same oxygen when breathing "welding grade", but no guarantees. RexxS (talk) 20:09, 6 January 2008 (UTC)[reply]

"The pipe bit" is not the whole story; as you say an important part of the filling process is ensuring that the cylinder is clean before it is filled. Any hospital or dive shop that "plugs" a patient or diver into a cylinder of welding grade oxygen is going to get a large legal bill if someone suffers as a consequence. If its a proper medical or diving cylinder, then BOC or its competitors carry the consequences of "dirty" product being supplied. Pyrotec (talk) 20:26, 6 January 2008 (UTC)[reply]

Gas quantity calculations

To calculate the quantity of gas:

 quantity of gas = volume x pressure

But:

3 litres * 200 bar = 60 kilojoules

Should the article clear this up? Also we might want to include some mention of the energy content (compressed air) of scuba tanks. —Preceding unsigned comment added by Glueball (talk • contribs) 11:55, 12 July 2007(UTC)

The formula only works in metric units - it's just Boyle's Law (and subject to the same limitations). Should be

"Volume of gas at atmospheric pressure = (cylinder volume) x (cylinder pressure) / (atmospheric pressure)"

I'll change it. And it would be of interest to show the energy stored in a cylinder - maybe with some comparisons to TNT, etc.? RexxS (talk) 20:29, 6 January 2008 (UTC)[reply]

A liter-bar is 100 J = 0.1 kJ, giving you the energy above, but this assumes that all the volume is delivered at this pressure, which if course is not the case in a scuba tank. As it charges, or as it explodes or discharges, the pressure runs up or down as the volume is delivered, so differential work at each instant changes, and the correct formula integrates the PV work over the whole process. There are two ways to do this: one is to assume that the heat or "cold" stays in the gas during the compression/decompression (a good assumption for charging a cylinder in air (say with fill-whip on a boat), or for one that explodes). The other way is to assume that compression heat leaks out to ambient temp, as in the tank-fill water bath (which is how you figure how much extra energy is, in a tank after it has cooled back down to room temp, and assuming that you discharge the gas so slowly that it has time to absorb surrounding heat which it can convert to work.)
The work to charge a tank VERY slowly and isothermally (or discharge it over an hour where the gas can warm up in the first stage), is W = P(1)V(1)ln (P2/P1). For a typical aluminum 80 at the surface, P1 is 11.3 L, P1 is 1 bar, P2 is 200 bar, so the work is 12,000 L-bar or so, or 1.2 MJ or 1200 kJ. This is 286 Cal, or about as much as in a candy bar. But no small potatoes energy-wise if released quickly, as a stick of dynamite is only 2100 kJ. So only half a stick of dynamite. In fact, for a fast adiabatic release, as in a tank explosion, it will be even less than this, since the gas will cool as it expands and does work on the environment, and thus will not do as much work as if it had been allowed to remain at the same temperature, absorbing heat in a slow expansion. S B H arris 00:58, 20 September 2009 (UTC)[reply]

This assumes a ideal gas. Air at 200 or 300bar is NOT an ideal gas. So 10L at 300bar ends up at only about 2700L air, a full 10% shy of the teoretical 3000L! --StefanHuszics (talk) 04:42, 19 May 2010 (UTC)[reply]

That's true and it's mentioned in the article. At 232 bar, the deviation from ideal gas law linearity is about 5% (assuming temperatures around 300 K). There's an article Compressibility factor that has lots of good data. --RexxS (talk) 05:09, 19 May 2010 (UTC)[reply]

Breathing Time

The formula and example are wrong, imho. They miss the point that ambient pressure should include the contribution of the weight of air above the water. In metric terms, you need to add 1 bar (or atmosphere - I know they're strictly not the same). The current formula leads to the conclusion that you can breathe off the cylinder for an infinite time at a depth of 0 metres! I would suggest:

AP = D * g * rho + atmospheric pressure

in proper units. However, gravity and water density are near constant compared to other variables, so this approximates to:

AP = D / 10 + 1

for all practical purposes. Remember that analogue depth gauges and analogue pressure gauges have errors both in linearity and readability, so there's little point in trying for absolute accuracy here when other variables can easily be out by 5% or more. Not forgetting of course that "depth gauges" work by measuring ambient pressure anyway, so correcting for water pressure is pointless as you really ought to correct the depth read by the same factor in the opposite direction - unless somebody has invented a dive computer that knows if it's diving in fresh or salt water. And of course, the biggest variable is breathing rate, which is difficult to keep within +/- 10% even for the most experienced divers.

Finally, there's no point in using the term (CP-AP) when CP is much greater than AP in all practical circumstances. If the purpose of this section is an illustration of how dives may be planned (rather than a sterile demonstration of how long before a cylinder becomes unusable), may I suggest that (CP-RP), where RP is the reserve pressure, would give more real-life information to the beginner and non-diver alike?

RexxS (talk) 21:40, 6 January 2008 (UTC)[reply]

Types of pillar valve - EN 144-3:2003

I'm looking at trying to clarify the sentence "From August 2008, these shall be required for all diving equipment used with Nitrox or pure oxygen."

The word that needs clarification is required. Required for what?

EN 144-3:2003 (ISBN: 0 580 41367 5) Respiratory protective devices. Gas cylinder valves. Outlet connections for diving gases Nitrox and oxygen does not address 'requirements' and is not legislation per se. It is true that if equipment is to be CE certified from August 2008, then it must comply with this European Norm. Note, though, that it says nothing about procedures for filling cylinders or using them safely. It certainly does not make the use of M25x2 connections illegal when used for nitrox or O2.

The EN which deals with requirements is in fact, EN 13949:2003 (ISBN: 0 580 41368 3) Respiratory equipment. Open-circuit self-contained diving apparatus for use with compressed Nitrox and oxygen. Requirements, testing, marking. It is interesting to see what EN 13949:2003 says about cylinder connections:

4.4 Pressure vessel valve(s)
Pressure vessel valve(s) shall comply with appropriate national or European Regulations and shall be approved and tested for use at the rated working pressure and pure oxygen. The threads for connecting the pressure vessel(s) and the valve(s) shall be M 18 x 1,5 or M 25 x 2 as specified in EN 144-1. Safe connection between the pressure vessel valve(s) and the demand regulator shall be ensured by using the connections as defined in EN 144-3.

So a little bit of drafting inexactitude? Both norms published on the same date, but the latter (although mentioning EN 144-3) fails to include M26x2 threads as permissible! --RexxS (talk) 23:13, 27 August 2008 (UTC)[reply]

Purposes of diving cylinders

Mark.murphy added the following: "To reduce the diver's high negative buoyancy when carrying many cylinders, divers often use aluminium stage cylinders because they are less dense than steel cylinders." I don't doubt that divers do that, but in most cases it's a mistake. Unless a diver has so much negative buoyancy that they have no weights, then the material of the cylinder is irrelevant: a properly weighted diver will be neutral with empty cylinders - the negative buoyancy at the start of a dive is simply the weight of air in the cylinders. All that aluminium cylinders do is increase the total volume of the diver+equipment, which means that they carry a greater total weight out of the water - not a desirable thing.

Anyway, I don't want to remove the statement, since I know that divers do use Al cylinders, mistakenly thinking that a less dense cylinder means less total negative buoyancy. But I'm concerned that the article now gives the wrong impression. This article isn't really the right place to present the arguments about buoyancy, correct weighting and choice of equipment. Is there an alternative formulation that would meet my concerns? --RexxS (talk) 15:19, 21 February 2009 (UTC)[reply]

Rexx, you are right. The explanation was not correct or complete. I have improved it.

Mark.murphy (talk) 18:11, 21 February 2009 (UTC)[reply]

Thanks Mark, you've made a good job of that - it explains well without the complexity I wanted to avoid. Cheers --RexxS (talk) 00:27, 22 February 2009 (UTC)[reply]

Spare Air

Although "Spare Air" is a trademark, that doesn't prevent the phrase being used in Wikipedia. Since the Spare Air is the only device of its type that I'm aware of, I'm unable to find a generic term to describe it. A "micro-aqualung" doesn't fit, since googling for that only brings up hits for the magical device used by James Bond in Thunderball or something similar used in Pokemon. I've referred to Spare Air by name and cited the website as the source. I must say that although I regard these devices as almost worthless, they exist and divers do use them, so they deserve a mention in the article. --RexxS (talk) 19:18, 19 September 2009 (UTC)[reply]

They are Bail-Out Bottles. Regardless of size. — Preceding unsigned comment added by 71.4.236.2 (talk) 14:51, 28 June 2011 (UTC)[reply]

References

For an article that is 36 kilobytes in size, there is a woeful lack of referencing to reliable sources. When assessing the article on the quality scale, I had difficulty in deciding if it should be a stub or start-class. There is one undoubtedly reliable source, but that is to a study mainly concerning impurities in the breathing gas (and is more relevant to the article on compressors). If there really is such a lack of sources, then perhaps this topic is not notable enough to warrant an article? --RexxS (talk) 15:02, 22 September 2009 (UTC)[reply]

The references are out there, but editors have choosen to add material without providing citations. Pyrotec (talk) 18:44, 22 September 2009 (UTC)[reply]

Photographs of "J" Valves. 1) incorporated in regulator, and 2) "J" Valve on Diving Cylinder.

These are two photographs which may add clarity and interest to the text of "Diving Cylinder". They are my photographs of my equipment taken yesterday, 2010-07-22, and are made available to you with my blessings. All substantiating paperwork is included in the "Gallery" with the .jpg images themselves.

As was mentioned, "J" Valves are not normally found today on modern equipment. However "J" Valves were incorporated in the earliest SCUBA gear from the time of Jacques Yves Cousteau and Emile Gagnon original invention and were the normal reserve systems until they became obsolete when high quality diving computers incorporating tank pressure gauges made them superfluous.

John W. Goodspeed "TheGoodspeeds (TheGoodspeeds (talk) 17:24, 23 July 2010 (UTC))[reply]

EU regulations

It's generally accepted that EU regulations require a diving cylinder to have a label that describes its contents. We know this because dive shops tell us so when we take in an old cylinder for a fill or test. However, here in the UK, it's not well-known what the relevant legislation actually says about diving cylinders, not least because it's not immediately obvious what the actual regulation number is.

There's a good leaflet from the UK Health and Safety Executive (INDG308(rev1) 4/02 C250), which is free to reproduce as long as the HSE is credited. A copy can be found online at http://www.lambaydiving.com/ukhse.pdf and it summarises the regulations that apply to the manufacture, testing, filling, and transportation of gas cylinders.

The standard EN 1089 Gas Cylinder Identification sets out the EU requirements for stamp marking, precautionary labels and colour coding. There's a summary online at http://www.ukdivers.net/equipment/cylinders.htm which is usually pretty accurate, but I wouldn't feel comfortable using it as a Wikipedia reliable source. I'll take a trip to the library this week to see if I can find the wording of the actual regulation. --RexxS (talk) 17:24, 13 November 2011 (UTC)[reply]

Orphaned references in Diving cylinder

I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of Diving cylinder's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "NOAA":

From Scuba diving: NOAA Diving Manual, 4th Edition, Best Publishing, 2001
From Scuba gas planning: National Oceanographic and Atmospheric Administration, (); NOAA Diving Manual, Fourth Edition, U.S. Department of Commerce National Technical Information Service, Springfield, VA

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT ⚡ 14:05, 27 November 2011 (UTC)[reply]

Poor "advantages" for manifolds

Re. the following text under "Manifolded twin set/doubles with two regulators":

"The pros of this configuration include [1] a large gas supply, [2] no requirement to change regulators underwater, [3] automatic gas supply management, and [4] in most failure situations the diver may close a failed valve or isolate a cylinder in order to leave himself with an emergency supply."

Let me use "manifolds" to mean a twin tank system where the two tanks are joined by a manifold; and "independents" to mean a twin tank system where the two tanks are totally independent.

[1], as stated, is just not true as an advantage of manifolds over independents. Two tanks, manifolded, have no more total gas than the same two tanks rigged independently. I suspect the author was actually thinking of [4].

[4] is true, but doesn't actually state the critical benefit of manifolds - namely, that closing valves or isolating cyclinders generally lets you retain access to *all* the remaining gas *on both sides* - unlike independents, where a failure on one side will generally result in losing access to all the gas on the failed side.

[3] is a poor choice of words. Most technical divers would understand "gas management" as meaning a range of things, such as, choosing the right size tanks for the dive; filling them to adequate pressures; being aware of differing personal gas consumption rates for different members of the team or group; following the "rule of thirds" when entering overhead environments, and so on. None of those things are specific to manifolds. All of them are equally applicable to independents.

I suggest replacing the quoted text with something like this:

"The pros of this configuration include: automatic balancing of the gas supply between the two tanks; thus, no requirement to constantly change regulators underwater during the dive; and in most failure situations, the diver may close a failed valve or isolate a cylinder and thus retain access to all the remaining gas in both the tanks."

TC 203.122.223.123 (talk) 11:15, 26 April 2013 (UTC)[reply]

Thank you for your well reasoned and constructive comment. It has been used in the article almost as stated. The advantage of a larger gas supply is valid when compared with a single cylinder (in most cases) and has been changed to specify that point. Gas management would include the balancing of available gas during a dive, but your version is unambiguous and an improvement on the original text. Please feel welcome to make further comments on any of the diving articles, and when you have an improvement which is unlikely to be controversial, you are free to edit the article yourself. It will be checked, and may be modified again, that is how this wiki works. Cheers, • • • Peter (Southwood) ^(talk): 16:45, 26 April 2013 (UTC)[reply]

Reader feedback: The web page could benifit f...

132.3.29.79 posted this comment on 1 August 2013 (view all feedback).

The web page could benifit from US equivalent information, as it caters to metric users. While the Aluminim 80 is mentioned almost as an afterthought, common tank sizes such as a steel 100 and steel 120 are completely missing. Also missing is a discusion of low pressure vs high pressure steel tanks.

This is a good point. Any volunteers? This equipment is not used much in my part of the world. Alternatively point me at a good reference. • • • Peter (Southwood) ^(talk): 09:11, 17 August 2013 (UTC)[reply]

Found some refs and added some content. Any comments? • • • Peter (Southwood) ^(talk): 16:12, 17 August 2013 (UTC)[reply]

The list gives the impression that these are the same for every cylinder of this type. This is frankly not correct. I have several sets of 12l tanks weighing ~14kgs. They generally seem to be about two KGs too heavy. Maybe this can be reworded to make clear that this is an example, because the general message is still true.

But overall, I do not see why there even needs to be this full table. I think it might suffice to say that 1L of tank volume at 200 Bars corresponds to ~250 grams of air, and maybe show the common 10/12/AL80s in comparison.