Diving cylinder

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A jumping cylinder , diving tank or diving tank is a gas tube used to store and transport the high pressure gas breathing required by the scuba set. It can also be used for dives provided on the surface or as a gas decompression or emergency gas supply for the surface provided by diving or scuba. Cylinders provide gas for divers through valve request diving regulator or respiratory loop from rebreather dive.

Diving cylinders are usually made of aluminum or steel alloy, and are usually equipped with one of two common types of cylinder valves for charging and connecting to the regulator. Other accessories such as manifolds, cylindrical tubes, protective nets and boots and carrier grips can be provided. Various harness configurations can be used to carry cylinders or cylinders while diving, depending on the application. Cylinders used for scuba typically have an internal volume (known as water capacity) between 3 and 18 liters (0.11 and 0.64 cm) and a maximum working pressure rating of 184 to 300 bar (2,670 to 4,350 psi). Cylinders are also available in smaller sizes, such as 0.5, 1.5 and 2 liters, but these are often used for purposes such as buoyancy, buoyancy, buoyancy rather than breathing buoyancy buoyancy inflation. Scuba divers can dive with a single cylinder, a pair of similar cylinders, or a smaller cylinder and a smaller "horse" cylinder, carried on the back of a diver or cut into a harness on the side. Paired cylinders can be manifold together or independently. In some cases, more than two cylinders are required.

When pressed, the cylinder carries the same free gas volume greater than its water capacity, since the gas is compressed up to several hundred times the atmospheric pressure. The selection of the right diving cylinder set for diving operation is based on the amount of gas required to complete the dive safely. Diving cylinders are most often filled with air, but because the main component of air can cause problems when breathing underwater at higher ambient pressure, a diver may choose to breathe from a cylinder filled with a gas mixture other than air. Many jurisdictions have rules governing charging, recording contents, and labeling for diving cylinders. Regular inspection and cylinder testing are often mandatory to ensure the safety of the charging station operators. Pressurized dive tubes are considered dangerous goods for commercial transport, and regional and international standards for staining and labeling may also apply.

Video Diving cylinder

Terminology

The term "diving cylinder" tends to be used by gas equipment engineers, producers, support professionals, and divers who speak English English. "Scuba tanks" or "diving tanks" are more commonly used daily by non-professional and native speakers of American English. The term "oxygen tank" is usually used by non-divers; However, this is a misnomer because this cylinder usually contains air air (compressed air), or a mixture of oxygen-rich air. They rarely contain pure oxygen, except when used for rebreather dives, shallow decompression stops at technical dives or for oxygen recompression therapy in water. Inhaling pure oxygen at a depth of more than 6 meters (20 feet) can cause oxygen toxicity.

Diving cylinders have also been referred to as bottles or flasks, usually preceded by scuba, diving, air, or bailout. Cylinders can also be called aqualung, a generic trademark derived from Aqua-Lung equipment manufactured by the Aqua Lung/La Spirotechnique company, although it is more appropriately applied to a series of open-circuit scuba or open circuit regulators.

The diving cylinder can also be determined by its application, such as on bailout cylinder, stage cylinder, deco cylinder, sidemount cylinder, horse cylinder, corresponding inflation cylinder, etc.

Maps Diving cylinder

Section

The functional diving cylinder consists of a pressure vessel and a cylinder valve. There is usually one or more optional accessories depending on the specific application.

Pressure vessel

Pressurized vessels are seamless cylinders typically made of cold extruded aluminum or forged steel. The wound filament composite tube is used in fire extinguishing aids and first aid oxygen equipment because of its low weight, but is seldom used for diving, due to its high positive buoyancy. They are sometimes used when portability to access dive sites is very important, like in cave dives. Composite cylinders certified to ISO-11119-2 or ISO-11119-3 can only be used for underwater applications if made in accordance with the requirements for underwater use and marked "UW".

Aluminum

A common cylinder especially provided in tropical diving resorts is "aluminum-S80" which is an aluminum cylinder design with an internal volume of 0.39 cubic feet (11.0Ã, l) rated to hold a nominal volume of 80 cubic feet (2,300 Ã, l) gas atmospheric pressure at a rated working pressure of 3,000 pounds per square inch (207 bar). Aluminum cylinders are also often used where divers carry many cylinders, such as in technical dive in warm enough water so the wetsuits do not provide much buoyancy, because the greater aluminum cylinder buoyancy reduces the amount of extra buoyancy required by divers. to achieve a neutral buoyancy. They are also sometimes preferred when taken as "sidemount" or "sling" cylinders as near neutral buoyancy allows them to hang comfortably along the diver's body side, without disturbing the trim, and they can be submitted to another diver or step down with minimal effect on buoyancy. Most aluminum cylinders have a flat base, allowing it to stand upright on a flat surface, but some are made with a dome base.

The aluminum alloys used for diving cylinders are 6061 and 6351. The 6351 alloys are subject to sustained load cracks and cylinders made from these alloys shall be periodically eddy currently tested in accordance with national legislation and manufacturer's recommendations. 6351 alloys have been replaced for new manufacture, but many old cylinders are still in service.

Aluminum cylinders are usually produced by cold extrusion of aluminum billets in a process that first presses against the wall and base, then cuts the top edge of the cylinder wall, followed by pressing to form the shoulders and neck. The final structural process is machining the outer surface of the neck, boring and cutting the neck thread and the O-ring groove. This cylinder is then heated, tested and stamped with the necessary permanent marks. Aluminum diving cylinders generally have a flat base, allowing them to stand upright on horizontal surfaces, and which are relatively thick to allow for rough and worn treatment. This makes them heavier than they should be for strength, but the extra weight on the base also helps keep the low center of gravity that provides better balance in the water and reduces the excess buoyancy.

Steel cylinder

In cold water dives, where a diver who wears a very floating thermal underwear has a great buoyancy, a steel cylinder is often used because it is denser than an aluminum cylinder. They also often have a lower mass of aluminum cylinders with the same gas capacity, due to much higher material strength, so the use of steel cylinders can produce both lighter cylinders and fewer ballasts required for the same gas capacity, two savings direction on the overall dry weight carried by the diver. Steel cylinders are more susceptible than aluminum to external corrosion, particularly in seawater, and can be galvanized or coated with corrosion barrier paint to resist corrosion. It is not difficult to monitor external corrosion, and repair paint when damaged, and well maintained steel cylinders have long lifetimes, often longer than aluminum cylinders, as they are not susceptible to fatigue damage when filled with safe working pressures. limit.

Steel cylinders are made with dome base (convex) and bottom (concave). Profile plates allow them to stand upright on horizontal surfaces, and are the standard form for industrial cylinders. Cylinders used for emergency gas supply on diving bells are often of this form, and generally have a water capacity of about 50 liters ("J"). The base of the dome gives larger volumes for the same mass of cylinders, and is standard for scuba cylinders up to 18 liters of water, although some underground concave cylinders have been marketed for scuba.

The alloy steels used for the manufacture of diving cylinders are authorized by manufacturing standards. For example, the US DOT 3AA standard requires the use of open-hearth, basic oxygen, or electric steels of uniform quality. The approved alloys include 4130X, NE-8630, 9115, 9125, Carbon-boron and manganese intermediates, with defined constituents, including manganese and carbon, and molybdenum, chromium, boron, nickel or zirconium.

Steel cylinders can be made from steel plate plates, cold ones drawn into cylindrical cups, in two or three stages, and generally have dome bases if intended for the scuba market, so they can not stand on their own. After forming the base and sides of the wall, the top of the cylinder is trimmed to long, heated and the heat rotates to form the shoulders and close the neck. This process thickened the shoulder material. This cylinder is heat treated with cooling and temper to provide the best strength and toughness. This cylinder is designed to provide the neck and o-ring seats (if any), then chemically cleaned or shot inside and outside to remove the plant scale. Upon examination and hydrostatic testing they are stamped with the necessary permanent markings, followed by an external layer with corrosion barrier paint or galvanizing.

Neckline

The neck cylinder is internally threaded to fit the cylinder valve. There are several standards for neck threads, these include:

• Taper yarn (17E), with 12% yarn twine, standard Whitworth 55 Â ° shape with pitch 14 threads per inch (5.5 threads per cm) and pitch diameter on a cylindrical thread of 18.036 millimeters ( 0.71 inches). These connections are sealed with screw and burned between 120 and 150 newton meters (89 and 111Ã, lbf? Ft) on steel cylinders, and between 75 and 140 N m (55 and 103 lbf? Ft) on aluminum cylinders. li>

Parallel threads are made for several standards:

• The ISO parallel thread, sealed by O-ring and torque of up to 100 ° to 130 °, Nm (74 to 96 × lbf ft) on steel, and 95 to 130 °, Nm (70 to 96 °, ) lbf? ft) on the aluminum cylinder;
• The M18x1.5 parallel thread, sealed by O-ring, and torque up to 100 ° to 130 °, Nm (74 to 96 lbf? ft) on a steel cylinder, and 85 to 100 N m (63 to 74 N lbf ? ft) on the aluminum cylinder;
• 3/4 "x14 parallel thread BSP, which has Whitworth 55 Â ° shape, pitch diameter 25,279 millimeters (0.9952 in) and pitch 14 threads per inch (1,814 mm);
• 3/4 "x14 NGS (NPSM) parallel thread, sealed by O-ring, burned up to 40 to 50 Â ° LU (30 to 37 μlbf) on aluminum cylinder, having 60 Â ° yarn shape, pitch diameter 0.9820 up to 0.9873 at (24.94 to 25.08 mm), and pitch 14 yarns per inch (5.5 threads per cm);
• 3/4 "x16Ã, UNF, sealed by O-ring, burned to 40 to 50Ã, N? m (30 to 37Ã, lbf? ft) on an aluminum cylinder.
• 7/8 "x14Ã, UNF, sealed by O-ring.

BSP 3/4 "NGS and 3/4" are very similar, have the same pitch and pitch diameter differing only about 0.2 mm (0.008 inches), but are not compatible, because the screw shape is different..

All parallel threaded valves are sealed using O-rings at the top of the neck thread that seals the chamfer or stepped on the cylinder neck and against the valve flange.

The cylindrical shoulder carries the stamp sign that provides the necessary information about the cylinder.

Cylinder valve

The purpose of the cylinder valve or pillar valve is to control the gas flow to and from the pressure vessel and to provide connection with the regulator or filling hose. Cylinder valves are usually done from brass and terminated by a protective and decorative layer of chrome plating. Metallic or plastic tubes or snorkel valves are screwed into the bottom of the valve extending into the cylinder to reduce the risk of particulate contaminants or liquid in the cylinder entering the part gas when the cylinder is inverted, and blocking or disturbing regulators. Some of these dip tubes have plain opening, but some have integral filters.

Cylinder valves are classified by four basic aspects: thread specifications, connection to regulators, pressure ratings, and distinguishing features. Standards relating to the specifications and manufacture of cylinder valves include ISO 10297 and CGA V-9 Standards for Cylinder Gas Cylinders.

Variations of cylinder thread

Cylinder threads may be in two basic configurations: Taper thread and parallel thread. The specification of the yarn is detailed in the previous section. The valve valve specification should be completely in accordance with the specifications of cylindrical neck thread. Unsuitable neck threads can fail under pressure and can be fatal.

Connection to regulator

Rubber <-o o-ring forms a seal between the metal pillar and metal valves of the dive regulator. Fluoroelastomers (eg viton) O-rings can be used with cylinders that store oxygen-rich gas mixtures to reduce the risk of fire. There are two basic types of cylinder valves for regulator connections commonly used for Scuba-containing air cylinders: connectors

• A-clamp or yoke - the connection on the regulator surrounds the valve pillar and suppresses the O-ring output from the pillar valve to the seat input. The connection is officially described as a CGAÃ, 850 yoke connection. The cuckoo is tightened firmly by hand (too hard can make the wood can not be removed later without tools) and the seal is made by clamping the O-ring between the surface of the regulator and the valve. When the valve is opened, the cylinder pressure extends the O-ring to the outer surface of the O-ring groove in the valve. Inadequate clamping force may allow pressure to remove the O-ring between the valve and the face regulator, resulting in leakage. This type of connection is simple, inexpensive and widely used throughout the world. It has a maximum pressure rating of 232 bar and the weakest part of the seal, O-ring, is not well protected from overpressure.
• DIN screw connector - the control screw into the cylinder valve traps the O-ring securely between the sealing surface of the valve and the O-ring groove on the regulator. This is more reliable than A-clamp because O-ring is well protected, but many countries do not use DIN fittings extensively on compressors, or cylinders that have DIN fittings, so divers traveling overseas with DIN systems may need to take an adapter, either to connect the DIN regulator to the rented cylinder, or to connect the A-clamp charger hose to the DIN cylinder valve.

There is also a cylinder valve for a gas cylinder other than air:

• New European Norms EN 144-3: 2003 introduces a new type of valve, similar to the existing 232 bar or 300 bar DIN valve, however, with the M26ÃÆ'-2 metric fit on the cylinder and regulator. It is intended to be used to inhale the gas with the above oxygen content normally found in natural air in the Earth's atmosphere (ie 22-100%). From August 2008, this is required in the EU for all dive equipment used with nitrox or pure oxygen. The idea behind this new standard is to prevent the rich mixture being filled into the unclean cylinder of oxygen. Yet even using a new system there still remains nothing except human procedural treatments to ensure that the cylinder with new valves is fixed clean-oxygen - which is exactly how the previous system worked.
• Men's cylindrical threaded valve M_ 24x2 is provided with some recreational rebreathers half-covered DrÃÆ'¤ger (DrÃÆ'¤ger Ray) for use with a mixture of nitrox. The regulator included with rebreather has a compatible connection.

Pressure value

The yoke valve has a value of between 200 and 240 bar, and there is no mechanical design detail that prevents connections between any yoke fittings, although some of the older yoke clamps will not match the 232/240 bar combination of the popular DIN/yoke cylinder valve as a yoke too narrow.

DIN valves are manufactured in 200 bars and a pressure rating of 300 bar. The number of threads and detailed configuration of the connections is designed to prevent any combination of attachment fillers or regulator attachments that do not fit the cylinder valve.

• 232 bar DIN (5-thread, G5/8) Outlet/Connector # 13 to DINÃ, 477 part 1 - (technically they are specified for cylinders with 300 bar test pressure)
• 300 DIN bars (7-thread, G5/8) Outlet/Connector # 56 to DINÃ, 477 part 5 - this is similar to a 5-thread DIN deployment but rated 300 bar working pressure. (Technically they are specified for cylinders with test pressure of 450 bar). The pressure of 300 bar is common in European diving and dive caves in the US.

The adapter is available to allow the DIN regulator connection to the yoke cylinder valve (adapter A-clamp or yoke), and to connect the yoke regulator to the DIN cylinder valve. (plug adapter and adapter block) The plug adapter is rated at 232/240 bar, and can only be used with valves designed to receive it. The block adapter is generally rated for 200 bars, and can be used with almost any DIN 200-bar valve.

Other distinguishing features

Plain valve

Cylinder valve type most commonly used is the single outlet exhaust valve, sometimes known as a valve "K", which allows the connection of a single regulator, and do not have a backup functionality. It's only open to allow gas flow, or shut down to turn it off. Some configurations are used, with the option of connection DIN or A-clamp, and a vertical spindle arrangement or transverse. The valve is operated by turning the knob, usually rubber or plastic, which gives a comfortable grip. Several rounds are required to open the valve completely. Some of the DIN valve can be converted into A-clamp by using inserts which are screwed into the hole.

Y and H The cylinder valve has two outlets, each with its own valve, allowing two regulators to be connected to the cylinder. If one of the regulators is "freeflows", which is a common failure mode, or ice, which can occur in water below about 5 ° C, the valve can be closed and the cylinder is inhaled from the regulator connected to the other valve. The difference between H-valve and Y-valve is that the Y-valve body is divided into two posts of approximately 90 ° to each other and 45 ° of the vertical axis, looks like Y, while the H-valve is usually strung from a valve designed as part of the manifold system with an additional valve post connected to the manifold socket, with vertical and vertical post posts, which look a bit like the H. Y valve also known as the "valve valve" due to their appearance.

Backup valve

Until the 1970s, when submersible pressure gauges on regulators began to be used publicly, diving cylinders often used mechanical backup mechanisms to show diver that the cylinder was nearly empty. The gas supply is automatically interrupted by a spring loaded valve when the gas pressure reaches reserve pressure. To release the reserve, the diver lowers the rod that runs along the side of the cylinder and that activates the lever to open the bypass valve. The diver will then complete the dives before the reserve (usually 300 pounds per square inch (21 bar)) consumed. Sometimes, divers will accidentally trigger a mechanism while wearing equipment or doing underwater motion and, unaware that the backup has been accessed, can find themselves out of the air in depth without any warning at all. These valves are known as "J-valves" of the "J" item in one of the first scuba equipment manufacturer's catalogs. The default non-reserve pair valve at that time is a "K" item, and is often still referred to as "K-valve". A j-valve is sometimes still used by professional divers in zero visibility, where the submersible pressure gauge (SPG) can not be read. While recreational submarine has stopped most of the support and sales of J-valve, US Department of Defense, US Navy, NOAA (National Oceanic and Atmospheric Administration) and OSHA (National Health and Safety Administration) all still allow or recommend the use of J-valves as an alternative to bailout tubes or as an alternative to pressure gauges that can be submerged. They are generally not available through the recreational dive shop, but are still available from several manufacturers. They can be significantly more expensive than the K-valves of the same manufacturer.

Less common in the 1950s to the 1970s was an R-valve equipped with a restriction that caused breathing to become difficult as the cylinder approached fatigue, but it would allow less breathing to be limited if the diver started to rise and the ambient water pressure decreased, providing more pressure differential big over the hole. It has never been so popular because if it is necessary for the diver to come down when out of the cave or wreck, breathing will become increasingly difficult as the diver goes deeper, eventually becoming impossible until the diver can rise to a low enough ambient pressure.

Hand valve

Some models of cylinder valves have axial spindles - in line with the cylinder axis, and are not submitted. The standard spindle-side valve has a valve knob on the right side of the diver when mounted backwards. The side spindle valve used with the manifold should be a pair of hands - one with the knob to the right and the other with the knob to the left, but in all cases the valve is opened by turning the switch counterclockwise, and closing by turning it clockwise. This is a convention with almost all valves for all purposes. The left-spindle valve is used by sidemount divers.

Explode disk

Some national standards require that the cylinder valve insert a bursting disc, a pressure relief device which releases gas before the cylinder fails in case of excess pressure. If a disc ruptures while diving the entire contents of the cylinder will disappear in a very short time. This risk occurs on properly measured disks, in good condition, on properly filled cylinders very low. Over-pressure protection of excess disks is specified in the CGA Standard S1.1. Standards for Pressure Aid Kit.

Accessories

Additional components for comfort, protection or other functions, are not directly required for function as pressure vessels.

Manifolds

The cylindrical manifold is a tube connecting two cylinders together so that the contents of both can be supplied to one or more regulators. There are three commonly used manifold configurations. The oldest type is a tube with connectors on each end attached to the cylinder valve hole, and an outlet connection in the middle, where the regulator is installed. Variations in this pattern include the spare valve in the outlet connector. Cylinders are isolated from the manifold when closed, and the manifold can be attached or disconnected when the cylinder is pressed.

Recently, a manifold has been available that connects the cylinder on the side of the valve cylinder, leaving the outgoing channel connection of the cylinder valve available for the regulator connection. This means that the connection can not be made or damaged when the cylinder is pressed, because there is no valve to isolate the manifold from the inside of the cylinder. This discomfort allows the regulator to be connected to each cylinder, and isolated from internal pressure independently, allowing the regulator to function on one cylinder to be isolated while still allowing the regulator to access the other cylinders to all the gas in the two cylinders. This manifold may be plain or may include an isolation valve in the manifold, which allows the contents of the cylinders to be separated from each other. This allows the contents of one cylinder to be isolated and secured for the diver if a leak in the cylinder neck thread, manifold junction, or disc burst on another cylinder causes the contents to be lost. The relatively unusual manifold system is a direct connection screwed to the neck of both cylinders, and has a single valve to release gas to the connector for the regulator. This manifold may include a spare valve, either in the main valve or on one cylinder. This system is mainly for historical purposes.

Valve enclosure

Also known as a cage manifold or regulator cage, it is a structure that can be clamped to a cylindrical neck or a manifold cylinder to protect the valves and the first-stage control of collisions and abrasion damage when in use and from rolling valves covered by handwheel friction against overhead. The cage valves are often made of stainless steel, and some designs can block obstructions.

Cylinder bands

The cylinder rope is a rope, usually of stainless steel, which is used to clamp two cylinders together as a set of twins. Cylinders can be manipulated or independent. It is common to use cylinders near the top of the cylinder, just below the shoulders, and one below. The conventional distance between the centrelines to bolt onto the backplate is 11 inches (280 mm).

Cylinder boot

The cylinder boot is a rubber or hard plastic cover that fits the dive cylinder base to protect the paint from abrasion and impact, to protect the cylinder surface from standing against the cylinder, and in the case of the lower round cylinder, to allow the cylinder to stand upright on its base. Some boots have flats that are molded into plastic to reduce the tendency of rolling cylinders on a flat surface. There is a possibility that in some cases there is water trapped between the boot and the cylinder, and if this is seawater and paint under the boot in bad condition, the cylinder surface may corrode in the area. This can usually be avoided by rinsing with clean water after use and stored in a dry place. Additional hydrodynamic barriers caused by cylinder booting are trivial when compared to overall dive drag, but some boot styles may present a slightly higher risk of snagging on the environment.

Cylinder net

The cylindrical net is a cylindrical net that extends over the cylinder and is tied up and down. This function to protect the painting from scratches, and on the booted cylinder, also helps to drain the surface between the boot and cylinder, which reduces the corrosion problem under the boot. The mesh size is usually about 6 millimeters (0.24 inches). Some divers will not use boots or nets as they can tear more easily than empty cylinders and are a pitfalls hazard in some environments like caves and junk interiors. Sometimes sleeves made from other materials can be used to protect the cylinder.

Cylinder handle

The cylinder handle can be mounted, usually clipped to the neck, to carry the cylinder comfortably. This can also increase the risk of getting caught in a closed environment.

Cover and dust plug

This is used to cover the cylinder valve opening when the cylinder is not used to prevent dust, water or other materials contaminating orifice. They can also help prevent the O-ring from falling yoke type valves. The plug can be removed so that the gas leak from the cylinder does not press the plug, making it difficult to remove.

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Rating pressure

The cylinder wall thickness is directly related to working pressure, and this affects the characteristic of the buoyancy force of the cylinder. Low pressure cylinders will be lighter than high-pressure cylinders with the same size and proportion to the diameter and in the same alloys.

Working pressure

Scuba cylinders are technically all high pressure gas containers, but in the US industry there are three commonly used nominal working pressure ratings (WPs);

low pressure (2400-2640 psi - 165 to 182 bars),

standard (3000 psi - 207 bars), and

high pressure (3300 to 3500 psi - 227 to 241 bar).

US-made aluminum cylinders typically have a standard working pressure of 3,000 pounds per square inch (210 Â ° bar), and the compact aluminum range has a working pressure of 3,300 pounds per square inch (230 Â ° bar). Some steel cylinders made with US standards are allowed to exceed a nominal working pressure of 10%, and this is indicated by the '' symbol. This extra pressure allowance depends on the cylinder that passes the corresponding higher standard periodic hydrostatic tests.

The parts of the world using a metric system usually refer to the direct cylinder pressure in the bar but generally will use "high pressure" to refer to 300 bar (4,400 psi) working pressure cylinder, which can not be used with the yoke connector on the regulator. 232 bar is a very popular working pressure for scuba cylinders in steel and aluminum.

Test pressure

The hydrostatic test pressure (TP) is determined by the manufacturing standard. This is usually a working pressure of 1.5 or in the US, 1.67 ÃÆ'â € "work pressure.

The developed pressure

The working pressure of the cylinder is determined at the reference temperature, usually 15 Â ° C or 20 Â ° C. and the cylinder also has a specified maximum safe working temperature, often 65 Â ° C. The actual pressure in the cylinder will vary according to temperature, as described by but this is acceptable in the case of a standard provided that the pressure developed when corrected to the reference temperature does not exceed the specified working pressure stamped on the cylinder. This allows the cylinder to be safely and legally charged to a higher pressure than the specified working pressure when the filling temperature is greater than the reference temperature, but not more than 65 Â ° C, provided that the filling pressure does not exceed that developed. the pressure for that temperature, and the cylinders charged in accordance with this provision shall be at the correct working pressure when cooled to the reference temperature.

Pressure monitoring

Internal pressure diving cylinders are measured at several stages when in use. It is checked before it is filled, monitored during charging and checked when charging is complete. This can all be done with pressure gauges on charging equipment.

Pressure is also generally monitored by divers. First as a content check before use, then as long as it is used to ensure that there is enough left at any time to allow for safe diving settlement, and often after dives for record keeping purposes and personal consumption level calculations.

Pressure is also monitored during hydrostatic testing to ensure that tests are performed for correct pressure.

Most diving cylinders do not have a special pressure gauge, but this is a standard feature on most dive regulators, and requirements on all filling facilities.

There are two broad standards for the measurement of dive gas pressure. In the US and possibly some other places, the pressure is measured in pounds per square inch (psi), and other parts of the world use bars. Sometimes gauges can be calibrated in other metric units, such as kilopascals (kPa) or megapascals (MPa), or in the atmosphere (atm, or ATA), especially gauges that are not actually used underwater.

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Capacity

There are two conventions commonly used to describe the capacity of a diving cylinder. One is based on the internal volume of the cylinder. The other is based on the volume of gas stored nominally.

Internal volume

Internal volumes are generally quoted in most countries using the metric system. This information is required by ISO 13769 to be stamped on the shoulder of the cylinder. This can be measured easily by filling the cylinder with fresh water. This results in the term 'water capacity', abbreviated as a frequently labeled WC marked on the shoulder of a cylinder. Almost always expressed as volume in liters, but sometimes as a water mass in kg. Fresh water has a density of approximately one kilogram per liter so that numerical values ​​are effectively identical to a precise decimal place.

Standard size with internal volume

This is a representative example, for a larger range, on-line catalogs from manufacturers such as Faber, Pressed Steel, Luxfer, and Catalina can be consulted. The app is distinctive, but not exclusive.

• 22 liters: Available in steel, 200 and 232bar,
• 20 liters: Available in steel, 200 and 232bar,
• 18 liters: Available in steel, 200 and 232 bar, used as single or twin for gas back.
• 16 liters: Available in steel, 200 and 232bar, used as single or twin for gas back.
• 15 liters: Available in steel, 200 and 232 bar, used as single or twin for gas back
• 12.2 liters: Available in 232, 300 bar and aluminum 232 bar, used as single or twin for gas back
• 12 liters: Available in 200, 232, 300 bar, and aluminum 232 bar, used as single or twin for gas back
• 11 liters: Available in aluminum, 200, 232 bar used as single, twin for back gas or sidemount
• 10.2 liters: Available in aluminum, 232 bar, used as single or twin for gas back
• 10 liters: Available in steel, 200, 232, and 300 bar, used as single or twin for gas back, and for bailout
• 9.4 liters: Available in aluminum, 232 bar, used for gas back or as a sling
• 8 liters: Available in steel, 200 bar, used for Semi-enclosed rebreathers
• 7 liters: Available in steel, 200, 232 and 300 bar, and aluminum 232 bar, gas returns as singles and twins, and as bailout cylinders. A popular size for SCBA
• 6 liters: Available in steel, 200, 232, 300 bar, used for gas back as single and twin, and as bailout cylinders. Also a popular size for SCBA
• 5.5 liters: Available in steel, 200 and 232 bar,
• 5 liters: Available in steel, 200 bar, used for rebreathers
• 4 liters: Available in steel, 200 bar, used for rebreathers and pony cylinders
• 3 liters: Available in steel, 200 bar, used for rebreathers and pony cylinders
• 2 liters: Available in steel, 200 bar, used for rebreathers, pony cylinders, and inflation suits
• 1.5 liters: Available in steel, 200 and 232 bar, used to adjust inflation
• 0.5 liters: Available in steel and aluminum, 200 bar, used for floating compensator and surface of inflation buoy signer

Nominal gas volume saved

The nominal volume of the stored gas is generally cited as the cylinder capacity in the US. This is a measure of the volume of gas that can be removed from the full cylinder at atmospheric pressure. Terms used for capacity include 'free gas volume' or 'free gas equivalent'. It depends on the internal volume and working pressure of the cylinder. If the pressure works higher, the cylinder will store more gas for the same volume.

The nominal working pressure does not have to be the same as the actual working pressure used. Some steel cylinders manufactured to US standards are allowed to exceed a nominal working pressure of 10% and this is indicated by the '' symbol. This extra pressure allowance depends on the cylinder that passes the corresponding periodic hydrostatic test and does not necessarily apply to US cylinders exported to countries of different standards. The nominal gas content of this cylinder is based on a 10% higher pressure.

For example, the common cylinder Aluminum 80 (Al80) is an aluminum cylinder that has a nominal 80 ft (2,300 liters) 'free gas' capacity when pressed up to 3,000 pounds per square inch (210 Â ° bar). It has an internal volume of 10.94 liters (0.386 cuÃ, ft).

Standard size based on stored gas volume

• Large Aluminum C100 (13. lÃ, l), high pressure (3,300 pounds per square inch (228Ã, bar)) cylinder. Weight 42.0 pounds (19.1 kg).
Aluminum S80 is probably the most common cylinder, used by resorts in many parts of the world for back gas, but also popular as a sling cylinder for gas decompression, and as a side-mounted cylinder in fresh water, as it has virtually neutral buoyancy. This cylinder has an internal volume of about 11 liters (0.39 cuÃ, ft) and a working pressure of 3,000 pounds per square inch (207 bar). They are also sometimes used as twin manifolds for back-mounting, but in these applications divers require more weights than most steel cylinders with equal capacity.
• Aluminum, C80 is the high-pressure equivalent, with a water capacity of 10.3Ã, l and a working pressure of 3,300 pounds per square inch (228Ã, bar).
• Aluminum S40 is a popular cylinder for side-mount and sling mount bailout and gas decompression for medium depth, due to small diameter and almost floating, which makes it relatively unobtrusive for this mounting style. The internal volume is about 5.8 liters (0.20 cm) and the working pressure is 3,000 pounds per square inch (207 bar).
Aluminum, S63 (9.0Ã, l) 3,000 pounds per square inch (207Ã, bar), and steel HP65 (8.2Ã, l) smaller and lighter than Al80, but has a lower capacity, and is suitable for smaller or shorter divers. dive.
• Steel LP80 2,640 pounds per square inch (182 bar) and HP80 (10.1Ã, Â ± l) at 3,442 pounds per square inch (237Ã, bar) are both more compact and lighter than AluminumÃ, S80 and both float negatively , which reduces the amount of ballast weight required by divers.
• Steel HP119 (14.8 Ã,)), HP120 (15,3Ã, l) and HP130 (16.0Ã, l) cylinders provide gas in greater quantities for nitrox or technical dive.

src: www.scubadoctor.com.au

Applications and configurations

Divers can carry one cylinder or multiple, depending on dive requirements. Where diving takes place in low-risk areas, where divers can safely make a free ascent, or where a friend is available to provide alternative air supply in an emergency, recreational divers usually only carry one cylinder. Where the risk of diving is higher, for example where visibility is low or when recreational divers dive deeper or decompress, and especially when diving under overhead, divers routinely carry more than one gas source.

Filtered cylinders can serve different purposes. One or two cylinders can be used as the primary breathing source that is meant to be inhaled for most of the dives. Smaller cylinders that are carried in addition to larger cylinders are called "horse bottles". Cylinders used purely as independent safety reserves are called "bailout bottles" or Emergency Gas Supply (EGS). Horse bottles are usually used as a bailout bottle, but this depends on the time it takes to bring it up.

Divers who perform technical dives often carry different gases, each in a separate cylinder, for each diving phase:

• "travel gas" is used during down and up. Usually air or nitrox with oxygen content between 21% and 40%. Gas travel is needed when the gas bottom is hypoxic and therefore it is not safe to breathe in shallow water.
• "bottom gas" just takes a deep breath. This is usually a low oxygen-based helium gas (below 21%) or hypoxia (below 17%).
• "deco gas" is used in decompression stops and generally one or more nitrox mixes with high oxygen content, or pure oxygen, to speed up decompression.
• a "stage" is a reserve of cylinder detention, travel or gas deco. They are usually brought in "side draped", cut off on both sides of the diver to the harness of the backplate and the buoyancy buoyancy compensator, rather than behind, and may be left in the line of distance to be taken for use on return (stage down). Generally divers use aluminum stage cylinders, especially in fresh water, as they are almost neutral floating in water and can be disposed of under water with less effect on the overall buoyancy of the diver.
• "Inflation gas suit" can be taken from respiratory gas cylinders or may be supplied from small independent cylinders.

For safety, divers sometimes carry additional independent scuba cylinders with their own regulators to reduce emergency situations outside the air if the main gas supply fails. For common recreational dives where controlled swimming hikes are safely accepted, these additional equipment are not required or used. This extra cylinder is known as a bail-out tube, and can be done in several ways, and can be any size that can withstand enough gas to make the diver return safely to the surface.

Scuba open circuit

Diving cylinders are used in rebreather diving in two roles:

• As part of rebreather itself. Rebels must have at least one source of fresh gas stored in a cylinder; many of which have two and some have more cylinders. Due to lower gas rebreathers consumption, these cylinders are typically smaller than those used for equivalent open circuit dives. Rebreathers can use internal cylinders, or may also be supplied from "off-board" cylinders, which are not directly thrown into the rebreather, but are connected to it with flexible hoses and couplings and usually carry the side slung.

• oxygen rebreathers has an oxygen tank
• semi-enclosed rebreathers have cylinders that usually contain nitrox or helium-based gas.
• rebreathers enclosed circuits have oxygen cylinders and "diluent" cylinders, which contain air, nitrox or helium-based gas.

• The rebreather diver also often brings an external bailout system if the internal diluent cylinder is too small for safe use for bailouts for planned dives. The bailout system is one or more independent respiratory gas sources to use if the rebreather should fail:
  • Open circuit : One or more series of open circuits. The number of open circuit bailout sets, their capacity, and the respiratory gas they contain depends on the depth and decompression requirements of the dive. So on deep and technical rebreather dives, divers will need gas "bottom" and gas "decompress" bailout. On such dives, usually the capacity and duration of a bailout set that limits the depth and duration of the dives - not the rebreather's capacity.
  • Closed circuit : A second rebreather containing one or more independent diving cylinders for its gas supply. Using another rebreather as collateral can happen but is unusual. Although the duration of the old rebreathers seems to be interesting for bail-outs, the rebreathers are relatively large, complex, prone to damage and require more time to start breathing, from the easy to use, open circuit equipments available directly, strongly and reliably.

Emergency emergency gas supply provided on surface

Surface-supplied suppliers are usually required to bring sufficient emergency gas supplies to enable them to return to safety if the main gas supply fails. The usual configuration is a rear-mounted single cylinder supported by a diver's safety harness, with a first-stage regulator connected to a low-pressure hose to a bailout block, which can be mounted on the side of a helmet or band-mask or on a harness to provide a full face mask that light. Where single cylinder capacity in unpaired or rebreather twins can be used. For a closed bell and diving saturation, the bailout set must be compact enough to allow the diver to pass the doorbell at the bottom of the bell. This sets limits on the size of a usable cylinder.

Emergency gas supply with diving bells

Diving bells are required to carry the gas supply of breathing for use in an emergency. Cylinders are installed externally because there is not enough space in them. They are fully submerged in water during bell operations, and can be considered as diving cylinders.

Match the inflation tube

Inflation gas suit can be done in small independent cylinders. Sometimes argon is used for superior insulation properties. It should be clearly labeled and may also need to be color-coded to avoid unintentional use as a respiratory gas, which can be fatal because argon is asphyxia.

Other uses of compressed gas cylinders in dive operations

Divers also use gas cylinders over water for oxygen storage for first-aid treatment of diving disorders and as part of "bank" storage for dive air compressor stations, gas mixing, supplied air-supply gas supply and gas supply for decompression chamber and saturation system. Similar cylinders are also used for many purposes that are not connected with diving. For these applications they are not diving cylinders and may not be subject to the same regulatory requirements as cylinders used under water.

src: www.coltri.com

Gas calculation

Keep in mind the approximate length of time a diver can breathe from a given cylinder so that a safe dive profile can be planned.

There are two parts to this problem: Cylinders and divers.

Capacity of cylinder to store gas

Two cylinder features determine the carrying capacity of the gas:

• internal volume: this usually ranges between 3 liters and 18 liters for one cylinder.
• Cylinder gas pressure: when charged it typically ranges between 200 and 300 bar (2,900 and 4,400 psi), but the actual value should be measured for real situations, since the cylinder may not be full.

To calculate the amount of gas:

Gas volume at atmospheric pressure = (cylinder volume) x (cylinder pressure)/(atmospheric pressure)

In parts of the world using the metric system the calculation is relatively simple because the atmospheric pressure can be estimated as 1 bar, So a 12-liter cylinder at 232 bar will store almost 12Ã,Â,Ã,Ã, 232Ã,ÂÃ,Ã,Â,Ã,Â,78,784 liter (98.3 cuÃ, ft) of air at atmospheric pressure (also known as free air).

In the US the capacity of dive cylinders is determined directly at the free cubic foot of air at nominal working pressure, because the calculation of the internal volume and work pressure is relatively boring in the imperial unit. For example, in the US and in many dive resorts in other countries, one might find aluminum cylinders from US manufacturing with an internal capacity of 0.39 cubic feet (11 liters) filled with 3,000 psi (210 bar) working pressure; At atmospheric pressure of 14.7 psi, this gives 0.39-3000/= 0.7.7 = 80 ft. This cylinder is described as "80 feet cubic cylinder", (general "aluminum 80").

Up to about 200 bars of ideal gas law remain valid and the relationship between pressure, cylinder size and gas contained in a linear cylinder; at higher pressures there is less gas in the cylinder. A 3-liter cylinder filled to 300 bar will carry only 810 liters (29 Â ° cuÃ, ft) atmospheric pressure gas instead of 900 liters (32 Â ° cuÃ, ft) expected from the ideal gas law.

Consumption of diver gas

There are three main factors to consider:

• the rate at which the diver consumes the gas, which is determined as the surface air consumption (SAC) or the respiratory minute volume (RMV) of the diver. Under normal conditions this would be between 10 and 25 liters per minute (L/min) for a non-working diver. At a very high work rate, the respiratory rate can rise to 95 liters per minute. For the purpose of International Marine Gas Association (IMCA) commercial gas entry planning, a working breathing rate of 40 liters per minute is used, while 50 liters per minute is used for emergencies. RMV is controlled by blood CO ₂ level, and usually does not depend on the partial pressure of oxygen, so it does not change with depth. The enormous range of possible gas consumption levels creates significant uncertainty as to how long the inventory will last, and a conservative approach is needed for safety where direct access to alternative gas sources is not possible. Scuba divers are expected to monitor the remaining gas pressure frequently enough so that they are aware of how much is still available at any time during the dive.
• ambient pressure: the depth of diving determines this. The ambient pressure at the surface is 1 bar (15 psi) at sea level. For every 10 meters (33 ft) in seawater, the diver drops, the pressure increases by 1 bar (15 psi). When the diver goes deeper, the respiratory gas is sent at the same pressure as the ambient water pressure, and the amount of gas used is proportional to the pressure. Thus, it takes twice as much gas mass to fill the dive lung at 10 meters (33 feet) as it does on the surface, and three times more at 20 meters (66 feet). Consumption of respiratory gas masses by divers is also affected.
• time in every depth. (usually approximated as time in each depth range)

To calculate the amount of gas consumed:

gas consumed = surface air consumption ÃÆ'â € "time ÃÆ'â €" ambient pressure

Example metrics:

A diver with RMV 20Ã, L/min at 30 msw (4 bars), will consume 20 x 4 x 1 = 80 ÃÆ'//min equivalent surface.

A diver with RMV 40Ã, L/min at 50 msw (6 bars) for 10 minutes will consume 40 x 6 x 10 = 2400 liters of free air - a full capacity of 12 liters 200 bar cylinders./dd>

Example of the empire:

A diver with SAC 0.5 cfm (cubic feet per minute) at 100Ã, fsw (4Ã, ata) will consume 0.5 x 4 x 1 = 2 cfm surface equivalent.

A diver with SAC 1 cfm at 231Ã, fsw (8Ã, ata) for 10 minutes will consume 1 x 8 x 10 = 80Ã, ft ³ from free air - full capacity of 80Ã, ft ³ cylinder

With this in mind, it is not difficult to see why technical divers who dive in the old need many cylinders or rebreathers, and commercial divers usually use submarine equipment provided on the surface, and only carry scuba as an emergency gas supply.

Respiratory gas resistance

The amount of time that a cylinder investigator can inhale is also known as air or gas resistance.

The maximum breathing duration (T) for a given depth can be calculated as

T = available air/consumption rate

which, using the ideal gas law, is

T = (available cylinder pressure ÃÆ'â € "cylinder volume)/(surface air consumption rate) ÃÆ'â €" (ambient pressure)

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(1) T = (P _C -P _A "P _A )

with

T = Time

P _C = Cylinder Pressure

V _C = Cylinder internal volume

P _A = Ambient Pressure

SAC = Surface air consumption

in a consistent unit system.

Ambient pressure (P _A ) is the surrounding water pressure at a certain depth and consists of the amount of hydrostatic pressure and air pressure on the surface. It is calculated as

(2) P _A = DÃÆ'â € "gÃÆ'â €"? atmospheric pressure

with

D = depth

g = Gravity standard

? = water density

in a consistent unit system

For metric units, this formula can be approached by

(3) P _A = D/10 1

with depth of m and pressure on the bar

The ambient pressure is subtracted from the cylinder pressure, since the quantity of air represented by P _A can in practice not be used to breathe by the diver because it is necessary to balance the ambient air pressure.

This formula ignores the crack pressure required to open the first and second stages of the regulator, and the pressure drop due to flow restriction in the regulator, both of which vary depending on the regulator's design and regulation, and the flow rate, which depends on the respiratory pattern of the diver and the gas used. These factors are not easily predicted, so the calculated value for the duration of breathing will be more than its true value.

However, in normal use of diving, reserves are always taken into account. Reserves are part of the cylinder pressure which the diver will not plan to use instead of in an emergency. The reserve may be one-quarter or one-third of the cylinder pressure or may be a fixed pressure, a common example is 50 bar and 500 psi. The above formula is then modified to provide a breathable duration that can be used as

(4) BT = (P _C -P _R ) ÃÆ' â € "V _C /(SACÃÆ'â € "P _A )

where P _R is a preset pres

For example, (using the first formula (1) for absolute maximum stop time), a diver at a depth of 15 meters in water with an average density of 1020 kg/mÃ,³ (ordinary sea water), which breathes at a rate of 20 liters per minute, using a 18 liter dive cylinder pressurized at 200 bar, can breathe for 72 minutes before the cylinder pressure drops very low to prevent inhalation. In some scuba systems this open circuit can occur suddenly, from a normal breath to the next abnormal breath, a breath that may not be completely withdrawn. (There was never any difficulty breathing). Suddenly this effect depends on the regulator's design and the internal volume of the cylinder. Under such circumstances there remains air under pressure in the cylinder, but the diver can not breathe it. Some of these can be inhaled if the diver rises, because ambient pressure is reduced, and even without climb, in some cylindrical airborne systems available to develop a buoyancy (BCD) compensator device even after it no longer has enough pressure to open the demand valve.

Using the same conditions and 50 bar reserves, the formula (4) for the breathing time that can be used is as follows:

Air pressure = water pressure atmospheric pressure = 15 msw/10 bar per msw 1 = 2.5 bar

Usable pressure = fill pressure - reserve pressure = 200 bar - 50 bar = 150 bar

Can be used = pressure that can be used ÃÆ'â € "cylinder capacity = 150 bar ÃÆ'â €" 18 liter per bar = 2700 liter

Consumption rate = surface air consumption ÃÆ'â € "ambient pressure = 20 liters per minute per bar ÃÆ'â €" 2.5 bar = 50 liters/min

Usable breathing time = 2700 liters/50 liters per minute = 54 minutes

This will give a 54-minute diving time at 15 m before reaching a reserve of 50 bar.

Backup

Highly recommended by diver training organizations and codes of practice that a portion of the gas that can be used from the cylinder should be stored as a safety reserve. Backup is designed to provide gas for the lon

Source of the article : Wikipedia