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Encyclopedia > Diving cylinder
12 litre and 3 litre steel diving cylinders

A diving cylinder, scuba tank or diving tank is used to store and transport high pressure breathing gas as a component of an Aqua-Lung. It provides gas to the SCUBA diver through the demand valve of a diving regulator. Diving cylinders are typically filled in the range of 186 to 300 bar (2700 to 4400 psi, or 18.6 to 30.0 MPa) and have a volume of 1.5 to 18 litres or a gas carrying capacity of 850 to 4200 litres (24 to 120 ft³). diving cylinder 12 and 3 litre File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... diving cylinder 12 and 3 litre File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Air is the most common and only natural breathing gas. ... ... Scuba diving is swimming underwater while using self-contained breathing equipment. ... A gas pressure regulator has one or more valves in series, which let the gas out of a gas cylinder in a controlled way, lowering its pressure at each stage. ...

Divers use gas cylinders above water for many purposes including storage of gases for oxygen first aid treatment of diving disorders and as part of storage "banks" for diving air compressor stations. They are also used for many purposes not connected to diving. Industrial compressed gas cylinders used for oxy-fuel welding and cutting of steel. ... Oxygen first aid kit showing a demand valve and a constant flow mask Oxygen first aid or oxygen administration is a first aid treatment for many medical emergencies involving the organs of respiration and circulation such as heart attack, drowning, carbon monoxide poisoning, decompression illness, lung barotrauma and gas embolism. ... Divers face specific physical and health risks when they go underwater (e. ... A Diving Air Compressor is a gas compressor, which can fill diving cylinders with high pressure air that is pure enough to be used as a breathing gas. ...

The term "diving cylinder" tends to be used by gas equipment engineers, manufacturers, support professionals, and divers speaking British English. "Scuba tank" or "diving tank" is more often used colloquially by non-professionals and native speakers of American English. British English (BrE, BE, en-GB) is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere in the Anglophone world. ... For other uses, see American English (disambiguation). ...

## Parts of a cylinder GA_googleFillSlot("encyclopedia_square");

A 15 litre, 232 bar cylinder with A clamp type pillar valve
A 12 litre, 232 bar cylinder with DIN type pillar valve

The diving cylinder consists of several parts: Image File history File links Diving_cylinder_a_clamp. ... Image File history File links Diving_cylinder_a_clamp. ... Image File history File links Diving_cylinder_din. ... Image File history File links Diving_cylinder_din. ...

• the pressure vessel is normally made of cold-extruded aluminium or forged steel. An especially common cylinder available at tropical dive resorts is an "aluminum-80" which is an aluminium cylinder rated to hold 80 ft³ of gas (at 1 bar) at its rated pressure of 3000 psi (i.e., its capacity is approximately 10 litres at 200 bar). Aluminium cylinders are used where divers carry many cylinders, such as in technical diving, because the greater buoyancy of aluminium cylinders reduces the extra buoyancy the diver would need to achieve neutral buoyancy. In cold water diving, where a diver wearing a highly buoyant thermally insulating dive suit has a large excess of buoyancy, steel cylinders are often used because they are denser than aluminium cylinders. Kevlar wrapped composite cylinders are used in fire fighting breathing apparatus and oxygen first aid equipment, but are rarely used for diving, due to their high positive buoyancy.
• the pillar valve is the point at which the pressure vessel connects to the diving regulator. The purpose of the pillar valve is to control gas flow to and from the pressure vessel and to form a seal with the regulator. Some countries insist that the pillar valve includes a burst disk, a type of pressure 'fuse', that will fail before the pressure vessel fails in the event of over pressurization.
• Y pillar valves. Most pillar valves only have one output and one valve. A Y valve has two outputs and two valves allowing two regulators to be connected to the cylinder. If one regulator “freeflows”, which is a common failure mode, its valve can be closed and the cylinder breathed from the regulator connected to the other valve.
• Reserve lever or "J-valve" (obsolete). Until the 1970s, when submersible pressure gauges on regulators came into common use, diving cylinders often used a mechanical reserve mechanism to indicate to the diver that the cylinder was nearly empty. The gas supply was automatically cut-off when the gas pressure reached the reserve pressure. To release the reserve, the diver pulled a lever and finished the dive before the reserve (typically 500 psi) was consumed. On occasion, divers would inadvertently trigger the mechanism while donning gear or performing a movement underwater and, not realizing that the reserve had already been accessed, could find themselves out of air at depth with no warning whatsoever. The J-valve got its name from being item number J in one of the first scuba equipment manufacturer catalogs. The standard non-reserve yoke valve at the time was item K, and is often still referred to as a K-valve.

Steel Pressure Vessel A pressure vessel is a closed, rigid container designed to hold gases or liquids at a pressure different from the ambient pressure. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... The steel cable of a colliery winding tower. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere. ... Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ... Chemical structure of Kevlar. ... Oxygen first aid kit showing a demand valve and a constant flow mask Oxygen first aid or oxygen administration is a first aid treatment for many medical emergencies involving the organs of respiration and circulation such as heart attack, drowning, carbon monoxide poisoning, decompression illness, lung barotrauma and gas embolism. ... In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i. ... These water valves are regulated by handles. ... Typical O-ring and application An O-ring is a loop of elastomer with a round (o-shaped) cross-section used as a mechanical seal. ... A gas pressure regulator has one or more valves in series, which let the gas out of a gas cylinder in a controlled way, lowering its pressure at each stage. ... Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms: fluorine, chlorine, bromine or iodine. ... Air is the most common and only natural breathing gas. ... The 1970s decade refers to the years from 1970 to 1979, also called The Seventies. ... Many techniques have been developed for the measurement of reduced or increased pressures. ...

## Types of pillar valve

A 232 DIN type pillar valve

There are three types of pillar valve: Image File history File links Metadata Size of this preview: 800 Ã— 600 pixelsFull resolution (2592 Ã— 1944 pixel, file size: 1. ... Image File history File links Metadata Size of this preview: 800 Ã— 600 pixelsFull resolution (2592 Ã— 1944 pixel, file size: 1. ... A pillar valve is the type of cylinder valve which is commonly found fitted to scuba cylinders. ...

• A-clamp or yoke - the connection on the regulator surrounds the valve pillar and presses the output O-ring of the pillar valve against the input seat of the regulator. This type is simple, cheap and very widely used worldwide. It has a maximum pressure rating of 232 bar and the weakest part of the seal, the o-ring, is not well protected from over-pressurisation.
• 232 bar DIN (5-thread, metric M 25×2) - the regulator screws into the pillar valve trapping the O-ring securely. These are more reliable than A-clamps because the o-ring is well protected, but many countries do not use DIN fittings widely on compressors, or cylinders which have DIN fittings, so a European diver with a DIN system abroad in many places will need to take an adaptor.
• 300 bar DIN : (7-thread, metric M 25×2) - these are similar to 5-thread DIN fitting but are rated to 300 bar working pressures. The 300 bar pressures are common in European diving and in US cave diving, but their acceptance in U.S. sport diving has been hampered by the fact that United States Department of Transportation rules presently prohibit the transport of metal scuba cylinders on public roads with pressures above about 230 bar, even if the cylinders and air delivery systems have been rated for these pressures by the American agencies which oversee cylinder testing and equipment compatibility for SCUBA (OSHA and CGA).

The new European Norm EN 144-3:2003 introduced a new type of valve, similar to existing 232 bar or 300 bar DIN valves, however, with a metric M 26×2 fitting on both the cylinder and the regulator. These are to be used for breathing gas with oxygen content above that normally found in natural air in the Earth's atmosphere (i.e., 22% –100%). From August 2008, these shall be required for all diving equipment used with Nitrox or pure oxygen. The idea behind this new standard is to prevent a rich mixture being filled to a cylinder, which is not oxygen clean. However even with use of the new system there still remains nothing except human procedural care to ensure that a cylinder with a new valve remains oxygen-clean - which is exactly how the current system works. Two A-clamps as used in scuba gear An A-clamp is a type of clamp very often used to make a pressure-tight high-pressure fastening in scuba gear. ... Typical O-ring and application An O-ring is a loop of elastomer with a round (o-shaped) cross-section used as a mechanical seal. ... Look up din in Wiktionary, the free dictionary. ... A pillar valve is the type of cylinder valve which is commonly found fitted to scuba cylinders. ... The United States Department of Transportation (DOT) is a federal Cabinet department of the United States government concerned with transportation. ... If you are searching for the organization, click OSHA. Osha (Ligusticum porteri) is a perennial herb used for its medicinal properties. ... CGA may stand for: Certified General Accountant Color Graphics Adapter This is a disambiguation page &#8212; a navigational aid which lists other pages that might otherwise share the same title. ... CEN, the European Committee for Standardization, was founded in 1961 by the national standard bodies in the European Economic Community and EFTA countries. ... Air is the most common and only natural breathing gas. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Layers of Atmosphere - not to scale (NOAA)[3] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Nitrox refers to any gas mixture composed (excluding trace gases) of nitrogen and oxygen; this includes normal air which is approximately 78% nitrogen and 21% oxygen, with around 1% other gases. ... An oxygen tank is a storage vessel for oxygen, which is either held under pressure in gas cylinders or as liquid oxygen in a cryogenic storage tank. ...

## Purposes of diving cylinders

Divers may carry one cylinder or multiples, depending on the requirements of the dive. In parts of the world where diving takes place in warm water and in good visibility, recreational divers usually carry only one cylinder. An example of this type is coral reef diving where it is possible to do an interesting dive without going deep or needing long decompression. Where diving risks are higher, for example in parts of the world where the water is cold and visibility is low or when recreational divers do deeper or decompression diving, divers routinely carry more than one gas source. An example of this type is north European diving where the temperature is often less than 15°C/60°F and visibility less than 10m/33ft and many interesting dive sites are shipwrecks in deeper water on the sea bed. Recreational diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. ... A Decompression Stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive in order safely to eliminate inert gases from the divers body to avoid decompression sickness. ... This article does not cite any references or sources. ...

Each cylinder may have a different purpose:

• primary breathing source - the cylinder intended for most of the dive,
• bail out or bale out - a cylinder used purely as an independent safety reserve,
• pony (bottle) - a small bail out.

Divers doing technical diving often carry different gases, each in a separate cylinder, for each phase of the dive: Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ...

• travel gas - a cylinder holding gas for use during the descent - typically a nitrox with a medium oxygen partial pressure
• bottom gas - a cylinder holding gas for use at depth - typically a helium-based gas with a low oxygen partial pressure, which is below 1.4 Atmospheres (absolute pressure) (ATA).
• deco - a cylinder holding gas for use at the decompression stop - typically nitrox with a high oxygen partial pressure, which is mostly around 1.6 ATA.
• stage - a cylinder holding the same gas as in you bottom gas cylinders, on your back.

Rebreathers also use internal cylinders: Nitrox refers to any gas mixture composed (excluding trace gases) of nitrogen and oxygen; this includes normal air which is approximately 78% nitrogen and 21% oxygen, with around 1% other gases. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ... A technical atmosphere (symbol: at) is a non-SI unit of pressure equal to 1 kilogram-force per square centimeter, i. ... A Decompression Stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive in order safely to eliminate inert gases from the divers body to avoid decompression sickness. ... A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. ...

• oxygen rebreathers have an oxygen cylinder
• semi-closed circuit rebreathers have a "diluent" cylinder, which often contains air, nitrox or a helium based gas
• closed circuit rebreathers have an oxygen cylinder and a "diluent" cylinder, which often contains air, nitrox or a helium based gas

## Breathing capacity

A commonly asked question is 'what is the underwater duration of a particular cylinder?'

There are two parts to this answer:

1. What is the cylinder's capacity to store gas?

Two features of the cylinder determine its gas carrying capacity:

• working gas pressure : this normally ranges between 200 bar/3000 psi and 300 bar/4400 psi
• internal volume : this normally ranges between 3 litres and 18 litres

To calculate the quantity of gas: The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin in Canberra, Australia. ... The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. ...

` quantity of gas = volume x pressure `

So a 3 litre cylinder at 200 bar would hold 600 litres (21.2 ft³) of air at atmospheric pressure.

Up to 200 bar the Ideal gas law remains valid and the relationship between the pressure, size of the cylinder and gas contained in the cylinder is linear; at higher pressures there is proportionally less gas in the cylinder. A 3 litre, 300 bar cylinder can only carry up to 810 litres (28.6 ft³) of atmospheric pressure gas and not the 900 litres expected from the Ideal gas law. Isotherms of an ideal gas The ideal gas law is the equation of state of a hypothetical ideal gas, first stated by BenoÃ®t Paul Ã‰mile Clapeyron in 1834. ...

2. How much gas does the diver consume?

There are three factors at work here:

• breathing rate or respiratory minute volume (RMV), in litres per minute (lpm), of the diver. In normal conditions this will be between 10 and 25 lpm. At times of high work rate or panic, breathing rates can rise to 100 lpm.
• time
• ambient pressure: the depth of the dive determines this. The ambient pressure at the surface is 1 bar / 14.7 psi. For every 10 metres/33 feet in salt water the diver descends, the pressure increases by 1 bar / 14.7 psi. As a diver goes deeper, the diver's lungs are compressed and this must be offset by breathing gas at a pressure equal to ambient water pressure. Thus, it requires twice as much mass of gas to fill the same volume (the diver's lungs) at 10 metres/33 feet as it does at the surface. This equation repeats itself with each bar of pressure. If a given cylinder consumed at a constant rate would last a diver one hour at the surface, it would last thirty minutes at 10 metres/33 feet, 20 minutes at 20 metres/66 feet and just 15 minutes at 30 metres/99 feet.

To calculate the quantity of gas consumed:

` gas consumed = breathing rate x time x ambient pressure `

Thus, a diver with a breathing rate of 20 lpm will consume at 30 meters (4 bar) the equivalent of 80 lpm at 1 bar (80 lpm at the surface). If this diver only had a 3 litre 200 bar cylinder to breathe from, the gas in the cylinder would be exhausted after a little over 600/80 = about 7.5 minutes.

Keeping this in mind, it is not hard to see why technical divers who do long deep dives require multiple cylinders or rebreathers. Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ... A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. ...

## Breathing Time

Using the ideal gas law, breathing time (BT) can be calculated as An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of zero volume, with no intermolecular forces. ...

$BT = frac {(CP-AP)*CS} {BR*AP}$

with

BT = Breathing Time (in minutes)

CP = Cylinder Pressure (in bars)

CS = Cylinder Size (in liters)

AP = Ambient Pressure (in bars)

BR = Breathing Rate (in liters per minute)

and where ambient pressure (AP) is calculated as

$AP = frac {D*g*rho} {100000}$

with

D = Depth (in meters)

g = Standard gravity (in meters per square second) g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ...

ρ = Water Density (in kg per cube meter)

AP is deducted from CP, as the quantity of air represented by AP can in practice not be used for breathing by the diver as she needs it to overcome the pressure of the water (AP) when exhaling.

For example (using the formula above), a diver at a depth of 15 meters in water with an average density of 1020 kg / m³ (typical salt water), who breaths at a rate of 20 liters per minute, using a dive cylinder of 18 liters pressurized at 200 bars, can breath for a period of 119 minutes before the ambient pressure starts (i) preventing her from exhaling and (ii) crushing her chest (put differently, there will still be air in the cylinder, but she would simply be unable to breathe it).

## Reserves

It is strongly recommended that a portion of the usable gas of the cylinder be held aside as a safety reserve. The reserve is designed to provide gas for longer than planned decompression stops or to provide time to resolve underwater emergencies. A Decompression Stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive in order safely to eliminate inert gases from the divers body to avoid decompression sickness. ...

The size of the reserve depends upon the risks involved during the dive. A deep or decompression dive warrants a greater reserve than a shallow or a no stop dive. In recreational diving for example, it is recommended that the diver plans to surface with a reserve remaining in the cylinder of 500 psi, 50 bar or 25% of the initial capacity, depending of the teaching of the diver training organisation. This is because recreational divers practicing within "no-decompression" limits can normally make a direct ascent in an emergency. On technical dives where a direct ascent is either impossible (due to overhead obstructions) or dangerous (due to the requirement to make decompression stops), divers plan larger margins of safety using the rule of thirds: one third of the gas supply is planned for the outward journey, one third is for the return journey and one third is a safety reserve. Recreational diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. ... This page lists SCUBA diver training organizations. ... In scuba diving, the rule of thirds is a rule of thumb that divers use to plan dives so they do not consume all the breathing gas from the diving cylinder before the end of the dive. ...

Some training agencies teach the concept of minimum gas and provide a simple calculation that allows a diver to work out an acceptable reserve to get two divers in an emergency to the surface. See DIR diving for more information. DIR, an acronym for Doing It Right, is an holistic approach to scuba diving originally developed by members of the Woodville Karst Plain Project. ...

## Configuring cylinders

15 litre, 232 bar, A clamp single cylinder open circuit breathing set
7 litre, 232 bar, DIN pillar valve independent twin set. The left cylinder shows manufacturer markings. The right cylinder shows test stamps
Manifolded twin 12 litre, 232 bar breathing set with two DIN pillar valves and two regulators
Two 3 litre, 232 bar, DIN cylinders inside a Inspiration Diving Rebreather closed circuit breathing set

### Open-circuit

For open-circuit divers, there are several options for the combined cylinder and regulator system:

• Single cylinder or single aqualung: consists of a single large cylinder with one first-stage regulator, and usually two secondary regulator/mouthpieces. This configuration is simple and cheap but it is only a single system: it has no redundancy in case of failure. If the cylinder or first-stage regulator fails, the diver is totally out of air and faces an emergency. All training agencies train divers to rely on a buddy to assist them in this situation. The skill of gas sharing is required at the most basic scuba course. This equipment configuration, although common with entry-level divers and for most sport diving, is not recommended for any dive that is deeper than 30 m or where decompression stops are needed, or where there is an overhead environment (wreck diving, cave diving, or ice diving). Generally, these conditions, because they prevent immediate emergency ascent, define technical diving.
• Main cylinder plus a small independent cylinder: this configuration uses a larger, main cylinder along with an independent smaller cylinder, often called a "pony". The diver has two independent systems, but the total 'breathing system' is now heavier, more expensive to buy and maintain.
• The pony is typically a 2 to 5 litre cylinder. Its capacity determines the depth of dive and decompression duration for which it provides protection. Ponies are generally fixed to the diver's buoyancy compensator (BC) or main cylinder behind the diver's back. They can also be clipped to the BC at the diver's side or chest. Ponies provided an acceptable emergency supply but are only useful if the diver trains to bail out, i.e. to use one.
• Another type of separate small air source is a micro-aqualung: a hand-held 0.5 litre cylinder with a diving regulator directly attached. This source provides a few breaths of gas and is suitable as a shallow water bailout, say from a maximum of 10 metres / 33 feet.
• Independent twin set/doubles: this consists of two independent cylinders and two regulators. This system is heavier, more expensive to buy and maintain and more expensive to fill. Also the diver must swap demand valves during dive to preserve a safety reserve of air in each cylinder. If this is not done, then should a cylinder fail the diver may end up having no reserve. Independent twin sets do not work well with air-integrated computers - as they usually only monitor one tank. Many divers feel the complexity of switching regulators periodically to ensure both cylinders are evenly used is offset by the redundancy of two entirely separate breathing supplies.
• Manifolded twin set/doubles with a single regulator: two cylinders are joined at their pillar valves with a manifold but only one regulator is attached to the system. This makes it simple and cheap but means there is no redundant breathing system, only a double gas supply.
• Manifolded twin set/doubles with two regulators: consist of two cylinders with their pillar valves joined with a manifold with a valve that can isolate the two pillar valves. In the event of a problem with one cylinder the diver may close the isolator valve to preserve gas in the cylinder, which has not failed. The pros of this configuration are you have a large gas supply, there is no need to change regulators underwater, management of gas supply is automatic, and in most failure situations, the diver may close a failed valve or isolate a cylinder, to leave himself with an emergency supply. The cons of this solution is that there is a danger of losing all air if the manifold valve cannot be closed when a problem occurs and the manifold is another potential point of failure. This configuration of cylinders is often used in Technical diving.
• Stage bottles/cylinders: are a type of independent cylinder used for technical diving. They are independent cylinders with their own regulators. Their primary purpose is not to provide redundant gas supply, but rather to carry either "stage", "travel" or "decompression" breathing gas while the main cylinder carries "bottom" gas.

This article does not cite any references or sources. ... Inside the cave at Cave Stream, New Zealand Caving is the recreational sport of exploring caves. ... Ice diving is a type of penetration diving where the dive takes place under ice. ... Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ... A buoyancy compensator (or buoyancy control device, BC or BCD) is a piece of diving equipment worn by divers to provide: life saving emergency buoyancy both underwater and on the surface. ... A gas pressure regulator has one or more valves in series, which let the gas out of a gas cylinder in a controlled way, lowering its pressure at each stage. ... Schematic representation of double diving cylinders connected with isolating manifold. ... Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ... Technical diving is a form of SCUBA diving that exceeds the scope of recreational diving. ... Air is the most common and only natural breathing gas. ...

### Closed-circuit

Diving cylinders are used in closed-circuit diving in two roles:

• As part of the rebreather itself. The rebreather must have at least one source of fresh gas stored in a cylinder; many have two and some have more cylinders. Due to the lower gas consumption of rebreathers, these cylinders typically are smaller than those used for equivalent open-circuit dives. See the main article: rebreather.
• In a bail out system: rebreather divers often carry one or more redundant gas sources should the rebreather fail:
• Open-circuit: a simple diving cylinder and regulator. The number of open-circuit bail outs, their capacity and the breathing gases they contain depend on the depth and decompression needs of the dive. So on a deep, technical rebreather dive, the diver will need a bail out "bottom" gas and a bail out "decompression" gas for use. On such a dive, it is the capacity and duration of the bail out that limits the depth and duration of the dive - not the capacity of the rebreather.
• Closed-circuit: a rebreather containing a diving cylinder and regulator. Using another rebreather as a bail out is possible but uncommon. Although the long duration of rebreathers seems compelling for a bail out, rebreathers are relatively bulky, complex, vulnerable to damage and require more time to start breathing from, than easy-to-use, instantly available, robust and reliable open-circuit equipment.

A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. ...

## Filling tanks

Tanks should only be filled with air from diving air compressors or with other breathing gases using gas blending techniques. Both these services should be provided by reliable suppliers such as dive shops. Breathing industrial compressed gases can be lethal because the high pressure increases the effect of any impurities in them. Look up air in Wiktionary, the free dictionary. ... A Diving Air Compressor is a gas compressor, which can fill diving cylinders with high pressure air that is pure enough to be used as a breathing gas. ... Air is the most common and only natural breathing gas. ... Air, oxygen and helium gas blending system Gas blending or gas mixing is the filling of diving cylinders with non-air breathing gases. ...

Special precautions need to be taken with gases other than air:

• oxygen in high concentrations is a major cause of fire and rust.
• oxygen should be very carefully transferred from one tank to another and only ever stored in tanks that are certified and labeled for oxygen use.
• gas mixtures containing proportions of oxygen other than 21% could be extremely dangerous to divers who are unaware of the proportion of oxygen in them. All cylinders should be labeled with their composition.

Contaminated air at depth can be fatal. Common contaminants are: carbon monoxide a by-product of combustion, carbon dioxide a product of metabolism, oil and lubricants from the compressor. Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ... In order to meet Wikipedias quality standards, this article requires cleanup. ...

The blast caused by a sudden release of the gas pressure inside a diving cylinder makes them very dangerous if mismanaged. The greatest risk of explosion exists at filling time and comes from thinning of the walls of the pressure vessel due to corrosion. Another cause of failure is damage or corrosion of the threads and neck of the cylinder where the pillar valve is screwed in. Aluminium cylinders have been observed occasionally to fail explosively, fragmenting the cylinder wall. Steel cylinders usually remain mostly intact, and tend to fail at the neck.

Keeping the cylinder slightly pressurized at all times reduces the possibility of contaminating the inside of the cylinder with corrosive agents, such as sea water, or toxic material, such as oils, poisonous gases, fungi or bacteria.

## Manufacture and testing

Most countries require tanks to be checked on a regular basis, see gas cylinder. This usually consists of an internal visual inspection and a hydrostatic test. In the United States, a visual inspection is required every year, and a hydrostatic every five years. In European Union countries a visual inspection is required every 2.5 years, and a hydrostatic every five years. In Norway a hydrostatic (including a visual inspection) is required 3 years after production date, then every 2 years. Industrial compressed gas cylinders used for oxy-fuel welding and cutting of steel. ... A hydrostatic test is the normal way in which a gas pressure vessel such as a gas cylinder or a boiler is checked for leaks or flaws. ...

Legislation in Australia requires that cylinders are hydrostatically tested every twelve months, regardless.

A hydrostatic test involves pressurising the cylinder to its test pressure and measuring its volume before and after the test. A permanent increase in volume above the tolerated level means the cylinder fails the test and should be destroyed.

When a cylinder is manufactured, its specification, including Working Pressure, Test Pressure, Data of Manufacture, Capacity and Weight are stamped on the cylinder.

On testing, the test date, or the test expiry date in some countries such as Germany, is punched into the neck of the tank for easy verification at fill time. Note: this is a European requirement.

Most compressor operators check these details before filling the cylinder and may refuse to fill non-standard or out-of-test cylinders. Note: this is a European requirement and a requirement of the USA DOT.

## Gas cylinder colour coding

In the European Union gas cylinders are beginning to be colour coded according to EN 1098-3. The "shoulder" is the top of the cylinder close to the pillar valve. For mixed gases, the colours can be either bands or "quarters".

• Air has either a white (RAL 9010) top and black (RAL 9005) band on the shoulder, or white (RAL 9010) and black (RAL 9005) "quartered" shoulders.
• Heliox has either a white (RAL 9010) top and brown (RAL 8008) band on the shoulder, or white (RAL 9010) and brown (RAL 8008) "quartered" shoulders.
• Nitrox, like Air, has either a white (RAL 9010) top and black (RAL 9005) band on the shoulder, or white (RAL 9010) and black (RAL 9005) "quartered" shoulders.
• Pure oxygen has a white shoulder (RAL 9010).
• Pure helium has a brown shoulder (RAL 9008).
• Trimix has a white, black and brown segmented shoulder.

Note: As of the end of 2006, the quartered parts is obsolete, and new cylinders are now with the band, and the old system is repainted.[citation needed] RAL is a color space system developed in 1927 by ReichsausschuÃŸ fÃ¼r Lieferbedingungen (und GÃ¼tesicherung)â€”German for Commission for Delivery Terms and Quality Assurance, nowadays called . ...

Worldwide, in many recreational diving settings where air and nitrox are the widely used gases, nitrox cylinders are colour-coded with a green stripe on yellow bottom. The normal colour of aluminium diving cylinders is their natural silver. Steel diving cylinders are often painted, to reduce corrosion, mainly yellow or white to increase visibility. In some industrial cylinder identification colour tables, yellow shoulders means chlorine and more generally within Europe it refers to cylinders with Toxic and/or Corrosive contents; but this is of no significance in SCUBA since gas fittings would not be compatible. Recreational diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. ... See corrosive for the hazard. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... // Toxic and Intoxicated redirect here â€“ toxic has other uses, which can be found at Toxicity (disambiguation); for the state of being intoxicated by alcohol see Drunkenness. ...

## Cylinder labeling

A contents label for oxygen usage

In the European Union breathing gas cylinders must be labeled with their contents. The label should state the type of breathing gas contained by the cylinder. Image File history File links Diving_cylinder_oxygen_label. ... Image File history File links Diving_cylinder_oxygen_label. ... Air is the most common and only natural breathing gas. ...

Cylinders that are subject to gas blending with pure oxygen also need an "oxygen service certificate" label indicating they have been prepared for use in an oxygen-rich environment. Air, oxygen and helium gas blending system Gas blending or gas mixing is the filling of diving cylinders with non-air breathing gases. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ...

## References

• CEN. EN 1098-2: Transportable gas Cylinders, Part 2 - Precautionary labels.
• CEN. EN 1098-3: Transportable gas Cylinders, Part 3 - Colour coding.

Results from FactBites:

 Diving cylinder - Wikipedia, the free encyclopedia (2813 words) Diving cylinders are typically filled in the range of 186 to 300 bar (2700 to 4300 psi, or 18.6 to 30.0 MPa) and have a volume of 1.5 to 18 litres or a gas carrying capacity of 850 to 3600 litres (30 to 120 ft³). Diving cylinders until the 1970s, before pressure gauges on regulators came into common use, often used a mechanical reserve mechanism to indicate to the diver that the cylinder was nearly empty. In recreational diving for example, it is recommended that the diver plans to surface with a reserve remaining in the cylinder of 500 psi, 50 bar or 25% of the initial capacity, depending of the teaching of the diver training organisation.
 NOAA Ocean Explorer: Scuba Diving (690 words) Scuba diving is the most extensively used system for breathing underwater by recreational divers throughout the world, and in various forms is also widely used to perform underwater work for military, scientific and commercial purposes. Cylinders for scuba diving are made of steel or aluminum alloy, and are designed to operate safely at pressures ranging from 2,250 to 3,500 psi (pounds per square inch). The primary function of the “demand regulator” attached to the diving cylinder is to reduce the high-pressure gas supplied by the scuba cylinder to the ambient pressure surrounding the diver at depth.
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