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Sustainability in Joining
Published in R. Ganesh Narayanan, Jay S. Gunasekera, Sustainable Material Forming and Joining, 2019
In gas welding (or flame welding), various fuels are combined with oxygen to generate heat required for welding. The fuels used are acetylene, methylacetylene-propadiene, hydrogen, propylene, and propane. If acetylene is used, which is predominantly the case; it is called oxyacetylene gas welding. Filler rod is not mandatory, but if used, it is coated with flux responsible for protecting weld pool from atmosphere. In oxyacetylene gas welding, combustion occurs in two stages. In the first stage, the products are CO and H2, which further undergoes reaction in the second stage, resulting in CO2 and heat generation. The combined heat generated is about 50 × 106 J/m3 of acetylene. In gas welding, the important sustainability and green contribution to the process comes in the form of fuel (e.g., acetylene or propane) and the type of flame (e.g., neutral or reducing or oxidizing) used for combustion. Methods of storing acetylene and materials for hoses are also crucial. The combination of acetylene and oxygen is highly flammable, and hence oxyacetylene welding is not eco-friendly and unsafe for workers.
Annotated Dictionary of Construction Safety and Health
Published in Charles D. Reese, James V. Edison, Annotated Dictionary of Construction Safety and Health, 2018
Charles D. Reese, James V. Edison
Fire prevention and protection requirements, applicable to underground construction operations, are to be followed. Open flames and fires are to be prohibited in all underground construction operations, except as permitted for welding, cutting, and other hot work operations. Smoking may be allowed only in areas free of fire and explosion hazards. Readily visible signs prohibiting smoking and open flames are to be posted in areas having fire explosion hazards. The employer is not permitted to store underground more than a 24-hour supply of diesel fuel for the underground equipment used at the worksite. The piping of diesel fuel, from the surface to an underground location, is permitted only if the diesel fuel is contained at the surface. This fuel must be in a tank which has a maximum capacity of no more than the amount of fuel required to supply, for a 24-hour period, the equipment serviced by the underground fueling station. The surface tank is to be connected to the underground fueling station by an acceptable pipe or hose system, and this system is to be controlled at the surface by a valve, and at the shaft bottom by a hose nozzle. The pipe is to be empty at all times, except when transferring diesel fuel from the surface tank to a piece of equipment in use underground. In the shaft, hoisting operations are to be suspended during refueling operations, if the supply piping, in the shaft, is not protected from damage. Gasoline is not to be carried, stored, or used underground. Acetylene, liquefied petroleum gas, and methylacetylene propadiene stabilized gas may be used underground only for welding, cutting, and other hot work.
Fire Hazards of Materials and Their Control
Published in Peter M. Bochnak, Fire Loss Control, 2020
Gases can also be classified by physical properties. Compressed gases exist in a gaseous state under pressure at normal temperatures in a container. The pressures can range from 25 to 3000 psig. Examples of compressed gases are oxygen, ethylene, hydrogen, and acetylene. Liquefied gases exist in a partly gaseous and partly liquid state under pressure at normal temperatures in a container. Normally, a liquefied gas is much more concentrated than is a compressed gas, usually at orders of magnitude more volume when released to the atmosphere. Examples are liquefied petroleum gas (LPG) and methylacetylene-propadiene, stabilized (MPS).
A combined experimental and computational study on the reaction dynamics of the 1-propynyl (CH3CC, X2A1) – propylene (CH3CHCH2, X1A′) system: formation of 1,3-dimethylvinylacetylene (CH3CCCHCHCH3, X1A′) under single collision conditions
Published in Molecular Physics, 2023
Iakov A. Medvedkov, Anatoliy A. Nikolayev, Chao He, Zhenghai Yang, Alexander M. Mebel, Ralf I. Kaiser
In deep space, propylene was detected toward TMC-1 with fractional abundances of 2 ×10−9 [98], while 1-propynyl is highly likely to be present in TMC-1 since its precursor methylacetylene holds a high fraction in TMC-1 up to 1×10−8 [60,61]. Therefore, we may predict that 1,3-dimethylvinylacetylene can be formed easily in TMC-1. Analogues barrierless reactions of the ethynyl radical with fractional abundances of 5 ×10−9 in OMC-1 [99] with propylene [78], and of 1-propynyl with ethylene (CRL 618 [100]) [54] may operate in cold molecular clouds. Once methyl- and dimethyl derivatives of vinylacetylene have been formed, these hydrogen deficient reactants may engage in fundamental molecular mass growth processes upon reactions with phenyl radials (C6H5) [29] and tolyl radicals (CH3C6H5) [31] via the barrierless HAVA mechanism (Figure 6). These processes can then yield to the formation of methyl and dimethyl naphthalenes thus providing a versatile route to methyl substituted aromatics and leading to a better understanding of the question ‘How alkylated PAHs form in interstellar medium?’.
Performance, combustion and emission analysis of internal combustion engines fuelled with acetylene – a review
Published in International Journal of Ambient Energy, 2022
Sumit Sharma, Dilip Sharma, Shyam Lal Soni, Digambar Singh, Amit Jhalani
There are many alternative fuels are available and is being used regularly, and many of research has been done on alternative fuels but due to increasing energy demand day by day, engine efficiency and environmental concern some of the further research should be necessary for alternative fuels. Among the commercially available gaseous fuel such as natural gas, liquefied petroleum gas (LPG), hydrogen and MAPP (Methylacetylene Propadiene Propane) gas, ‘Acetylene’ most closely meets all the above requirements. The properties of acetylene, conventional fuels and other gaseous fuels shown in Table 1.
Can third-body stabilisation of bimolecular collision complexes in cold molecular clouds happen?
Published in Molecular Physics, 2022
Zhenghai Yang, Srinivas Doddipatla, Chao He, Shane J. Goettl, Ralf I. Kaiser, Ahren W. Jasper, Alexandre C. R. Gomes, Breno R. L. Galvão
Which factors could enhance these prerequisites? First, a facile intersystem crossing and efficient spin–orbit coupling (SOC) could be facilitated through the ‘heavy atom effect’ [63,64] and hence barrier-less bimolecular reactions initiated by, e.g. silicon atoms (Si(3P)) with unsaturated hydrocarbons such as diacetylene as studied here. Although ground state silicon atoms do not react with astronomically abundant C1 to C3 hydrocarbons such as methane (CH4), acetylene (C2H2), ethylene (C2H4), methylacetylene (CH3CCH), allene (H2CCCH2), propylene (C3H6) and even benzene (C6H6) via bimolecular reactions [65], early kinetics experiments by Canosa et al. and Basu and Husain proposed fast reaction rates of up to a few 10−10 cm3 s−1 of the reactions of Si(3P) with unsaturated hydrocarbons at temperatures as low as 15 K [66,67]. These discrepancies might be reconciled by accounting for a barrierless entrance channel, facile non-adiabatic dynamics along with intersystem crossing from the triplet to the singlet surface, no available bimolecular reactive exit channels, and a re-crossing of the reaction intermediates from the singlet to the triplet surface. These processes could enhance the lifetime of the reaction intermediates so that the organosilicon adducts can be stabilised through a third body with the buffer gas in the CRESU studies thus implicating potential reaction pathways to an organosilicon chemistry in deep space at ultralow temperatures. Note that ‘light’ atoms of the second row of the periodic system of the elements such as ground state atomic oxygen (O(3P)) also undergo ISC upon reaction with unsaturated hydrocarbons such as methylacetylene (CH3CCH), allene (H2CCCH2), and benzene (C6H6) [68–70]; however, these bimolecular reactions have entrance barriers ranging from 6.7 to 15.9 kJmol−1, which cannot be overcome at typical cold molecular cloud temperatures of 10 K. Second, the life-time of the intermediates can be enhanced by increasing the availability of oscillators such as low frequency bending fundamentals along with ring deformation and puckering modes such as of polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium [3,71–73]. This could in turn enhance the lifetime of intermediates formed via bimolecular collisions with ground state atomic silicon and potentially the lighter atomic carbon thus providing an unconventional route to previously neglected third-body regimes in deep space.