MAPP gas

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A set of MAPP and oxygen cylinders used for oxy-fuel welding and cutting. Compressed gas cylinders.mapp and oxygen.triddle.jpg
A set of MAPP and oxygen cylinders used for oxy-fuel welding and cutting.

MAPP gas was a trademarked name, belonging to The Linde Group, a division of the former global chemical giant Union Carbide, for a fuel gas based on a stabilized mixture of methylacetylene (propyne), propadiene and propane. The name comes from the original chemical composition, methylacetylene-propadiene propane. "MAPP gas" is also widely used as a generic name for UN 1060 stabilised methylacetylene-propadiene (unstabilised methylacetylene-propadiene is known as MAPD).

Contents

MAPP gas is widely regarded as a safer and easier-to-use substitute for acetylene. In early 2008, true MAPP gas production ended in North America when production was discontinued at the only remaining plant in North America that still manufactured it. However, many current products labeled "MAPP" are, in fact, MAPP substitutes. These versions are composed almost entirely of propylene with minuscule impurities of propane (<0.5%). [1]

Use

Genuine MAPP gas can be used in combination with oxygen for heating, soldering, brazing and even welding because of its high flame temperature of 2925 °C (5300 °F) in oxygen. Although acetylene has a higher flame temperature (3160 °C, 5720 °F), MAPP has the advantage that it requires neither dilution nor special container fillers during transport, allowing a greater volume of fuel gas to be transported at the same given weight, and it is much safer in use.

A MAPP/oxygen flame is not entirely appropriate for welding steel, due to the high concentration of hydrogen in the flame – higher than acetylene, but lower than any of the other petroleum fuel gases. The hydrogen infuses into the molten steel and renders the welds brittle. For small-scale welding with MAPP this is not a serious problem, as the hydrogen escapes readily, and MAPP/oxygen can in practice be used for welding small steel parts.

MAPP/oxygen was advantageously used in underwater cutting, which requires high gas pressures (under such pressures acetylene can decompose explosively, making it dangerous to use [2] ). However, underwater oxy/fuel gas cutting of any kind has been largely replaced by exothermic cutting [3] because it cuts more quickly and safely.

MAPP gas is also used in combustion with air for brazing and soldering, where it has a slight advantage over competing propane fuel because of its higher combustion temperature of 2,020 °C (3,670 °F) in air.

The biggest disadvantage of MAPP gas is cost; it is typically one-and-a-half times as expensive as propane at the refinery, and up to four times as expensive to the consumer. It is no longer used much in any large-scale industry – for larger scale users acetylene/oxygen is more economic than MAPP/oxygen when high flame temperatures are needed, and propane/air is more economic when big overall heating is needed.

However, for the small-scale user a MAPP/oxygen flame is still highly desirable, having higher flame temperatures and energy densities than any flame other than acetylene/oxygen, but without the dangers and inconveniences of acetylene/oxygen. Jewellers, glassbead makers, and many others find it very useful. Plumbers, refrigeration and HVAC engineers and other tradesmen also value the high heat capacity of the MAPP/air flame; MAPP was until recently widely used, supplied in small to medium size containers.

Blowtorches are used to brown and sear food cooked by low-temperature sous-vide techniques. Myhrvold recommends in Modernist cuisine: the art and science of cooking that MAPP gases should be used in preference to cheaper butane or propane as they produce higher temperatures with less risk of giving the food a gas flavour, as can happen with incompletely combusted gas. [4]

Physical properties

MAPP is colorless in both liquid and gas form. The gas has a pronounced acetylene-like or fishy odor at concentrations above 100 ppm, due to the addition of substituted amines as a polymerization inhibitor. Low molecular weight alkynes have strong odors. MAPP gas is toxic if inhaled at high concentrations.

The composition of the supplied gas has varied widely, with the gases as supplied by different repackagers/resellers at any one time varying, as well as the general composition varying over time, but a typical composition for an early Dow gas might be: methylacetylene (propyne) 48%, propadiene 23%, propane 27%. For a later Dow/Petromont gas propyne 30%, propadiene 14%, propylene 43%, propane 7%, C4H10 (isobutane, butane) 6% might be more typical.

Thermal properties

MAPP has an energy content of 21000 BTU/lb (13.57 kWh/kg) while acetylene's energy content is 25000 BTU/lb (16.15 kWh/kg). [5]

Safety

People can be exposed to MAPP gas or its substitutes in the workplace by inhaling the gas or skin/eye contact with the liquid. The Occupational Safety and Health Administration (OSHA) has set the legal limit for MAPP gas exposure in the workplace as 1000 ppm (1800 mg/m3) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 1000 ppm (1800 mg/m3) over an 8-hour workday and 1250 ppm (2250 mg/m3) for short-term exposure. At levels of 3400 ppm, 10% of the lower explosive limit, MAPP gas is immediately dangerous to life and health. [6]

See also

Related Research Articles

Acetylene Chemical compound

Acetylene (systematic name: ethyne) is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas (lower hydrocarbons are generally gaseous in nature) is widely used as a fuel and a chemical building block. It is unstable in its pure form and thus is usually handled as a solution. Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities such as divinyl sulfide and phosphine.

Combustion Chemical reaction

Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion does not always result in fire, because a flame is only visible when substances undergoing combustion vaporize, but when it does, a flame is a characteristic indicator of the reaction. While the activation energy must be overcome to initiate combustion, the heat from a flame may provide enough energy to make the reaction self-sustaining.

Propane Hydrocarbon compound

Propane is a three-carbon alkane with the molecular formula C3H8. It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel in domestic and industrial applications and in low-emissions public transportation. Discovered in 1857 by the French chemist Marcellin Berthelot, it became commercially available in the US by 1911. Propane is one of a group of liquefied petroleum gases. The others include butane, propylene, butadiene, butylene, isobutylene, and mixtures thereof. Propane has a lower energy density but burns more cleanly than gasoline and coal.

Brazing High-temperature soldering; metal-joining technique by high-temperature molten metal filling

Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal.

Propyne Chemical compound

Propyne (methylacetylene) is an alkyne with the chemical formula CH3C≡CH. It is a component of MAPD gas—along with its isomer propadiene (allene), which was commonly used in gas welding. Unlike acetylene, propyne can be safely condensed.

Propene, also known as propylene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like odor.

Bottled gas Gas compressed and stored in cylinders

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

The heating value of a substance, usually a fuel or food, is the amount of heat released during the combustion of a specified amount of it.

Lithium hydride Chemical compound

Lithium hydride is an inorganic compound with the formula LiH. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not soluble but reactive with all protic organic solvents. It is soluble and nonreactive with certain molten salts such as lithium fluoride, lithium borohydride, and sodium hydride. With a molecular mass of slightly less than 8.0, it is the lightest ionic compound.

Oxyhydrogen Explosive mixture of hydrogen and oxygen gases

Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases. This gaseous mixture is used for torches to process refractory materials and was the first gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame.

Flashback arrestor Welding equipment

A flashback arrestor or flash arrestor is a gas safety device most commonly used in oxy-fuel welding and cutting to stop the flame or reverse flow of gas back up into the equipment or supply line. It protects the user and equipment from damage or explosions. These devices are mainly used in industrial processes where oxy-fuel gas mixtures are handled and used. Flashback arrestors as safety products are essential to secure the workplaces and working environment. In former times wet flashback arrestors were also used. Today the industry standard is to use dry flashback arrestors with at least two safety elements.

Propane torch Tool for generating heat and flame by burning propane

A propane torch is a tool normally used for the application of flame or heat which uses propane, a hydrocarbon gas, for its fuel. Propane is one of a group of by-products of the natural gas and petroleum industries known as liquefied petroleum gas (LPG). Propane and other fuel torches are most commonly used in the manufacturing, construction and metal-working industries.

Gas burner Device used to make fire from combusting fuel and oxidizer gases

A gas burner is a device that produces a controlled flame by mixing a fuel gas such as acetylene, natural gas, or propane with an oxidizer such as the ambient air or supplied oxygen, and allowing for ignition and combustion.

Oxy-fuel welding and cutting Metalworking technique using a gaseous fuel and oxygen

Oxy-fuel welding and oxy-fuel cutting are processes that use fuel gases and oxygen to weld or cut metals. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903. Pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the workpiece material in a room environment. A common propane/air flame burns at about 2,250 K, a propane/oxygen flame burns at about 2,526 K, an oxyhydrogen flame burns at 3,073 K and an acetylene/oxygen flame burns at about 3,773 K.

Butane torch Tool for generating heat and flame by burning butane

A butane torch is a tool which creates an intensely hot flame using butane, a flammable gas.

Propadiene Chemical compound

Propadiene or allene is the organic compound with the formula H2C=C=CH2. It is the simplest allene i.e. a compound with two adjacent carbon double bonds. As a constituent of MAPP gas, it has been used as a fuel for specialized welding.

Soldering Process of joining metal pieces with heated filler metal

Soldering is a process in which two or more items are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the work pieces. In brazing, the work piece metal also does not melt, but the filler metal is one that melts at a higher temperature than in soldering. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes.

Methylacetylene-propadiene (MPS) gas is a type of fuel gas used in oxy-fuel welding and cutting torches, comprising a mixture of several gases.

Blowtorch Fuel-burning tool for applying flame and heat for various applications

A blowtorch is a fuel-burning tool used for applying flame and heat to various applications, usually metalworking.

Steam cracking Petrochemical process to break down saturated hydrocarbons in smaller molecules

Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter alkenes, including ethene and propene. Steam cracker units are facilities in which a feedstock such as naphtha, liquefied petroleum gas (LPG), ethane, propane or butane is thermally cracked through the use of steam in steam cracking furnaces to produce lighter hydrocarbons. The propane dehydrogenation process may be accomplished through different commercial technologies. The main differences between each of them concerns the catalyst employed, design of the reactor and strategies to achieve higher conversion rates.

References

  1. ↑ See for example, "MAP-Pro" from BernzOmatic Archived 2015-05-03 at the Wayback Machine
  2. ↑ National Fire Protection Association (2010). Fire Protection Guide to Hazardous Materials (14th ed.). p. 49. https://pubchem.ncbi.nlm.nih.gov/compound/Acetylene#section=Decomposition&fullscreen=true Archived 2021-05-21 at the Wayback Machine
  3. ↑ "Exothermic cutting" uses the heat of burning steel wire to cut metals and even non-metals (e.g., concrete). Typically, the wire is ignited electrically and combustion is sustained via a flow of compressed oxygen. See: U.S. Navy Underwater Cutting & Welding Manual, NAVSEA S0300-BB-MAN-010 (1 June 2002), Chapter 2, especially sections 2.3 (Exothermic electrodes) and 2.4 (Seeler Enterprises LU-001 Exothermic Cutting Tool (Kerie Cable)), pages 53–74 (pages 2–22 to 2–43 of original document). Available on-line at: http://www.maritime.org/doc/pdf/cut_weld.pdf Archived 2014-10-30 at the Wayback Machine .
  4. ↑ Myhrvold, Nathan (2011). Modernist cuisine: the art and science of cooking. Vol. 2: Techniques and Equipment. Bellevue, Wash: Cooking Lab. p. 274. ISBN   978-0-9827610-0-7. OCLC   711381030.
  5. ↑ Self, Charles R. (1982). Do Your Own Professional Welding. Blue Ridge Summit, PA: Tab Books Inc. ISBN   0-8306-0068-X.
  6. ↑ "CDC – NIOSH Pocket Guide to Chemical Hazards – Methyl acetylene-propadiene mixture". www.cdc.gov. Archived from the original on 2022-01-25. Retrieved 2015-11-20.
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