Gas cylinder
Overview
 
A gas cylinder is a pressure vessel
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...

 used to store gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

es at above atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

. High pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 gas cylinders are also called bottles
Bottled gas
Bottled gas is a term used for substances which are gaseous at standard temperature and pressure and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders.-Gas state in cylinders:...

. Although they are sometimes colloquially called "tanks
Storage tank
A storage tank is a container, usually for holding liquids, sometimes for compressed gases . The term can be used for reservoirs , and for manufactured containers. The usage of the word tank for reservoirs is common or universal in Indian English, American English and moderately common in British...

", this is technically incorrect, as a tank is a vessel used to store liquids at ambient pressure and often has an open top.
In the United States, "bottled gas" typically refers to liquefied petroleum gas. "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tank
Oxygen tank
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.Oxygen tanks are used to store gas for:* industrial processes including the manufacture of steel and monel...

s.
Encyclopedia
A gas cylinder is a pressure vessel
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...

 used to store gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

es at above atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

. High pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 gas cylinders are also called bottles
Bottled gas
Bottled gas is a term used for substances which are gaseous at standard temperature and pressure and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders.-Gas state in cylinders:...

. Although they are sometimes colloquially called "tanks
Storage tank
A storage tank is a container, usually for holding liquids, sometimes for compressed gases . The term can be used for reservoirs , and for manufactured containers. The usage of the word tank for reservoirs is common or universal in Indian English, American English and moderately common in British...

", this is technically incorrect, as a tank is a vessel used to store liquids at ambient pressure and often has an open top.

Nomenclature differences

In the United States, "bottled gas" typically refers to liquefied petroleum gas. "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tank
Oxygen tank
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.Oxygen tanks are used to store gas for:* industrial processes including the manufacture of steel and monel...

s. Packaged industrial gases are frequently called "cylinder gas", though "bottled gas" is sometimes used.

The United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and other parts of Europe more commonly refer to "bottled gas" when discussing any usage whether industrial, medical or liquefied petroleum. However, in contrast, what the United States calls liquefied petroleum gas is known generically in the United Kingdom as "LPG"; and it may be ordered using by one of several Trade name
Trade name
A trade name, also known as a trading name or a business name, is the name which a business trades under for commercial purposes, although its registered, legal name, used for contracts and other formal situations, may be another....

s, or specifically as butane
Butane
Butane is a gas with the formula C4H10 that is an alkane with four carbon atoms. The term may refer to any of two structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, butane refers only to the unbranched n-butane isomer; the other one being called "methylpropane" or...

 or propane
Propane
Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...

 depending on the required heat output.

Materials

For a detailed discussion about the materials for gas cylinders see Pressure vessel.

Design codes and application standards along with the cost of materials dictated the choice of steel with no weldings for most gas cylinders, treated to be anti corrosive. There have been some newly developed lightweight gas cylinders from composite materials. Due to the very high tensile strength of carbon fibre, these vessels can be very light, but are much more difficult to manufacture.

Regulations and cylinder testing

The transportation of high pressure cylinders is regulated by many governments throughout the world. Various levels of testing are generally required by the governing authority for the country in which it is to be transported. In the United States, this authority is the United States Department of Transportation
United States Department of Transportation
The United States Department of Transportation is a federal Cabinet department of the United States government concerned with transportation. It was established by an act of Congress on October 15, 1966, and began operation on April 1, 1967...

 (DOT). Similarly in the UK, the European transport regulations (ADR) are implemented by the Department for Transport (DfT). For Canada, this authority is Transport Canada
Transport Canada
Transport Canada is the department within the government of Canada which is responsible for developing regulations, policies and services of transportation in Canada. It is part of the Transportation, Infrastructure and Communities portfolio...

 (TC). Cylinders may have additional requirements placed on design and or performance from independent testing agencies such as Underwriter's Laboratory (UL). Each manufacturer of high pressure cylinders is required to have independent quality agent that will inspect the product for quality and safety.

Within the UK the "competent authority" — the DfT — implements the regulations and appointment of authorised cylinder testers is conducted by UKAS, who make recommendations to the VCA for approval of individual bodies.

There are a variety of tests that may be performed on various cylinders. Some of the most common types of tests are hydrostatic test
Hydrostatic test
A hydrostatic test is a way in which leaks can be found in pressure vessels such as pipelines and plumbing. The test involves placing water, which is often dyed for visibility, in the pipe or vessel at the required pressure to ensure that it will not leak or be damaged. It is the most common method...

, burst test, tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...

, Charpy impact test
Charpy impact test
The Charpy impact test, also known as the Charpy v-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's toughness and acts as a tool to study temperature-dependent...

 and pressure cycling.

During the manufacturing process, vital information is usually stamped or permanently marked on the cylinder. This information usually includes the type of cylinder, the working or service pressure, the serial number, date of manufacture, the manufacture's registered code and sometimes the test pressure. Other information may also be stamped depending on the regulation requirements.

High pressure cylinders that are used multiple times — as most are — can be hydrostatically or ultrasonically tested and visually examined every few years. In the United States, hydrostatic/ultrasonic testing is required either every five years or every ten years, depending on cylinder and its service. Helium gas cylinders have the highest pressures possible when full, around 1000 atmospheres.

Valve connections

When gases are supplied in gas cylinders, the cylinders have a stop angle valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...

 at the end on top. Often, gas cylinders are somewhat long and narrow and may stand upright on a flattened bottom at one end with the valve at the top. During storage, transportation, and handling when the gas is not in use, a cap may be screwed over the protruding valve to protect it from damage or breaking off in case the cylinder were to fall over. Instead of a cap, cylinders commonly have a protective collar or neck ring around the service valve assembly.

When the gas in the cylinder is ready to be used, the cap is taken off and a pressure-regulating assembly is attached to the stop valve. This attachment typically has a pressure regulator
Pressure regulator
A pressure regulator is a valve that automatically cuts off the flow of a liquid or gas at a certain pressure. Regulators are used to allow high-pressure fluid supply lines or tanks to be reduced to safe and/or usable pressures for various applications....

 with upstream (inlet) and downstream (outlet) pressure gauges and a further downstream needle valve
Needle valve
A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.- Construction and operation :...

 and outlet connection. For gases that remain gaseous under ambient storage conditions, the upstream pressure gauge can be used to estimate how much gas is left in the cylinder according to pressure. For gases that are liquid under storage, e.g., propane, the outlet pressure is dependent on the vapor pressure of the gas, and does not fall until the cylinder is nearly exhausted. The regulator could be adjusted to control the flow of gas out of the cylinder according to pressure shown by the downstream gauge. The outlet connection is attached to whatever needs the gas supply, such as a balloon
Balloon
A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...

 for example.

The valves on industrial, medical and diving cylinders are usually of different size and type, as are the valves for different products, making it more difficult to mistakenly misuse a gas. Some fittings use a right-hand thread, while others use a left-hand thread
Screw thread
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...

; left-hand thread fittings are usually identifiable by notches cut into them.

In the United States, valve connections are sometimes referred to as "CGA connections," since the Compressed Gas Association (CGA) publishes guidelines on what connections to use for what products, e.g., In the United States, an argon cylinder will have a CGA 580 connection on the valve.

High purity gases will sometimes use CGA-DISS ("Diameter Index Safety System") connections.

In the EU, DIN
Deutsches Institut für Normung
is the German national organization for standardization and is that country's ISO member body. DIN is a Registered German Association headquartered in Berlin...

 connections are more common than in the United States.

Safety and standards

Because the contents are under pressure and are sometimes hazardous, there are special safety regulations for handling bottled gases. These include chaining bottles to prevent falling and breaking, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards. Installing and replacing gas cylinders should be done by trained personnel. If a compressed gas cylinder tips over, causing the valve block to be sheared off, the rapid release of high pressure gas may cause the cylinder to be violently accelerated, potentially causing property damage, injury, or death. To prevent this, cylinders are normally secured to a fixed object or transport cart with a strap or chain.

In a fire, the pressure in a gas cylinder rises in direct proportion to its temperature. If the internal pressure exceeds the mechanical limitations of the cylinder and there are no means to safely vent the pressurized gas to the atmosphere, the vessel will fail mechanically. If the vessel contents are ignitable, this event may result in a "fireball". If the cylinder's contents are liquid, but become a gas at ambient conditions, this is commonly referred to as a Boiling Liquid Expanding Vapour Explosion (BLEVE
BLEVE
A boiling liquid expanding vapor explosion occurs when a vessel containing a pressurized liquid above its boiling point ruptures.-Mechanism:...

).

Medical gas cylinders in the UK and other countries have a seal of Wood's metal
Wood's metal
Wood's metal, also known as Lipowitz's alloy or by the commercial names cerrobend, bendalloy, pewtalloy or MCP 158, is a eutectic, fusible alloy with a melting point of approximately . It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. It...

 between the valve block and the cylinder body. This seal melts at a comparatively low temperature (70°C) and allows the contents of the cylinder to escape in a controlled fashion, lessening the risk of explosion.

More common pressure relief devices are of a simple burst disc type. In these, a small burst disc is installed in the back of the valve. A burst disc is a small metal gasket engineered to rupture at a pre-determined pressure. Some burst discs are backed with a low-melting-point metal, so that the valve must be exposed to excessive heat before the burst disc can rupture.

The Compressed Gas Association
Compressed Gas Association
The Compressed Gas Association is the oldest major industrial and medical gas association in the world.In January 1913, Robert King sent a letter to the 75 manufacturers of compressed gases in the United States inviting them to attend a meeting in New York for the purpose of organizing a new...

 sells a number of booklets and pamphlets on safe handling and use of bottled gases.

Cylinders should be properly labeled and securely stored. Substances that may react with each other, e.g., oxidizers and flammable materials, should not be stored in close proximity.

International and US standards

  • ISO 11439: Gas cylinders — High pressure cylinders for the on-board storage of natural gas
    Compressed natural gas
    Compressed natural gas is a fossil fuel substitute for gasoline , diesel, or propane/LPG. Although its combustion does produce greenhouse gases, it is a more environmentally clean alternative to those fuels, and it is much safer than other fuels in the event of a spill...

     as a fuel for automotive vehicles
  • ISO 15500-5: Road vehicles — Compressed natural gas (CNG) fuel system components — Part 5: Manual cylinder valve
  • US DOT 3/4/8???: e-CFR (Electronic Code of Federal Regulations) Title 49, part 178, Subpart C - Specification for Cylinders
  • US DOT Aluminum Tank Alloy 6351-T6 ammendment for SCUBA, SCBA, Oxygen Service - Visual Eddy inspection

Color coding

Gas cylinders are often color coded, but the codes are not standard across different jurisdictions, and sometimes are not regulated. Cylinder color can not safely be used for positive product identification; cylinders have labels to identify the gas they contain and the label alone should be used for positive identification.

Common cylinder sizes

In scuba diving
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....

, the United States measures cylinder volume by the amount of free air that can be compressed into the cylinder; Europe measures the cylinder volume as the internal volume of the cylinder: e.g. United States 19 cubic feet = European 3 liter
Litér
- External links :*...

 at 180 bar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...

.

The below are example cylinder sizes and do not constitute an industry standard.
Cyl. Size Size* Diameter X Height (inches) Includes 5.5 inches for valve and cap. Nominal* Tare Weight (lbs.) Includes 4.5 lbs. for valve and cap. Water Capacity (lbs.) Internal Volume @ 70°F (21°C), 1 ATM liters (cubic feet) U.S. DOT Specs
K 9.25 X 60 135 110 49.9 (1.76) 3AA2400
A 9 X 51 115 96 43.8 (1.55) 3AA2015
B 8.5 X 31 60 37.9 17.2 (0.61) 3AA2015
C 6 X 24 27 15.2 6.88 (0.24) 3AA2015
D 4 X 18 12 4.9 2.24 (0.08) 3AA2015
AL 8 X 53 52 64.8 29.5 (1.04) 3AL2015
BL 7.25 X 39 33 34.6 15.7 (0.55) 3AL2216
CL 6.9 X 21 19 13 5.9 (0.21) 3AL2216
XL 14.5 X 50 75 238 108 (3.83) 4BA240
SSB 8 X 37 95 41.6 18.9 (0.67) 3A1800
10S 4 X 31 21 8.3 3.8 (0.13) 3A1800
LB 2 X 15 4 1 0.44 (0.016) 3E1800
XF 12 X 46 180 60.9 (2.15) 8AL
XG 15 X 56 149 278 126.3 (4.46) 4AA480
XM 10 X 49 90 120 54.3 (1.92) 3A480
XP 10 X 55 55 124 55.7 (1.98) 4BA300
QT 3 X 14 includes 4.5 inches for valve 2.5 includes 1.5 lbs for valve 2.0 0.900 (0.0318) 4B-240ET
LP5 12.25 X 18.25 18.5 47.7 21.68 (0.76) 4BW240
Medical E 4 x 26 excludes valve and cap 14 excludes valve and cap 4.5 (0.16) 3AA2015

See also

  • Bottled gas
    Bottled gas
    Bottled gas is a term used for substances which are gaseous at standard temperature and pressure and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders.-Gas state in cylinders:...

  • Pressure vessel
    Pressure vessel
    A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...

  • Carbon fiber
    Carbon fiber
    Carbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 5–10 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber...

  • Composite overwrapped pressure vessel
    Composite overwrapped pressure vessel
    A composite overwrapped pressure vessel is a vessel consisting of a thin, non-structural liner wrapped with a structural fiber composite, designed to hold a fluid under pressure...

  • Filling Carousel
    Filling Carousel
    A filling carousel is intended for filling liquified petroleum gas cylinders in large groups. It consist of a frame with running wheels, rails, a central column for LPG and air, and a driving unit the carousel frame around the central column. The speed of the carousel can be adapted to the...

  • Industrial gas
    Industrial gas
    Industrial gas is a group of gases that are commercially manufactured and sold for uses in other applications. These gases are mainly used in an industrial processes, such as steelmaking, oil refining, medical applications, fertilizer, semiconductors, etc.,...

  • Storage tank
    Storage tank
    A storage tank is a container, usually for holding liquids, sometimes for compressed gases . The term can be used for reservoirs , and for manufactured containers. The usage of the word tank for reservoirs is common or universal in Indian English, American English and moderately common in British...

  • UN Recommendations on the Transport of Dangerous Goods
    UN Recommendations on the Transport of Dangerous Goods
    The UN Recommendations on the Transport of Dangerous Goods are contained in two documents prepared by the Sub-Committee of Experts on the Transport of Dangerous Goods of the United Nations Economic and Social Council . They cover the transport of dangerous goods by all modes of transport except by...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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