In an industry typically receive acetylene from calcium carbide (CaC 2 ) the decomposition of the latter with water.
Acetylene ignites spontaneously at a temperature of 335 ° C, a mixture of acetylene with oxygen is ignited at a temperature of 297-306 ° C, a mixture of acetylene with air - at a temperature of 305-470 ° C.
Acetylene is explosive under the following conditions:
- with increasing temperature over 450-500 ° C and a pressure of 1.5-2 atm (150-200 kPa);
- at atmospheric pressure acetylene-oxygen mixture containing acetylene from 2.3 to 93% of the bursts of sparks, flame, strong local heating, etc.;
- under similar conditions a mixture of acetylene with air explodes when the content of acetylene in it from 2.2 to 80.7%;
- as a result of prolonged contact of acetylene with silver or copper is produced explosive atsetilenistoe silver or copper, exploding with increasing temperature or impact.
Safety measures when working with acetylene
- content of acetylene in the working area must be continuously monitored by automatic devices, signals exceeding the permissible concentration of acetylene in the explosion-proof air, equal to 0.46%;
- when dealing with acetylene cylinders should not be near an open flame or heating system, are prohibited from operating cylinders that are in a horizontal position, with loose cylinders, cylinders with faulty, you must use non-sparking tools, lighting and electrical equipment only explosion-proof;
- in case of leakage of acetylene from a cylinder (by smell and sound) should be possible to quickly close the cylinder valve sparking a special key;
- when heated with acetylene cylinder can explode with a very devastating consequences, in case of fire should be possible to remove from the danger zone with acetylene cylinders cool, always cool the remaining cylinders with water or special trains until cool; in fire acetylene escaping from the cylinder must be possible quickly close the cylinder valve key and special sparking water tank with water until cool, with a strong ignition of fire-fighting should be performed from a safe distance, when fighting fire extinguishers are recommended for use with content flegmatiziruyuschey nitrogen concentration 70% by volume of carbon dioxide 57% by volume water jet sand, compressed nitrogen, asbestos cloth, foam and water tokoraspylennuyu, with a strong suppression of fire retardants used costumes, masks, etc.
Acetylene - the main fuel gas used in gas welding , and is widely used for gas cutting (oxygen cutting). The temperature of the oxygen-acetylene flame can reach 3300 ° C. Because of this acetylene compared to the more accessible combustible gases (propane, butane, natural gas, etc.) provides a higher quality and productivity of welding.
Supply stations acetylene gas welding and cutting can be done
- from cylinders with acetylene and
- from the acetylene generator.
 |
| Technical characteristics of grades of acetylene (GOST 5457-75), used in welding and cutting. |
| Parameter | Acetylene Technology | |||
| dissolved grade B | gaseous | |||
| Class I | second-class | |||
| The volume fraction of acetylene, C 2 H 2 ,%, not less | 99,1 | 98,8 | 98,5 | |
| The volume fraction of air and other gases, slightly soluble in water,%, max | 0,8 | 1,0 | 1,4 | |
| The volume fraction of phosphine PH 3 ,%, max | 0,02 | 0,05 | 0,08 | |
| The volume fraction of hydrogen sulfide H 2 S,%, not more | 0,005 | 0,05 | 0,05 | |
| Mass concentration of water vapor at a pressure of 101.3 kPa (760 mm Hg. Art.) And 20 ° C, g / m 3 , not more | 0,5 | 0,6 | not rated | |
| -24 | -22 | ||
- improves safety when working with a balloon - at the expense of a porous mass of the total amount of acetylene is divided into separate cells, so that the probability distribution of the total combustion front and the explosion is significantly reduced;
- allows to increase the amount of acetylene in the cylinder, to accelerate the process of dissolving while filling the cylinder and the allocation for the selection of gas - as the use of a porous mass, impregnated with acetone, provides large surface area of mutual contact between the gas and acetone.
40-liter tanks with a maximum gas pressure of 1.9 MPa at 20 ° C is usually filled with acetylene 5-5,8 kg (4,6-5,3 m 3 of gas at a temperature of 20 ° C and 760 mm Hg. Art. .) The mass of acetylene in the cylinder is determined by the mass difference between the cylinder before and after filling with gas. The volume of acetylene is the ratio of its mass and density. Thus, the amount of 5.5 kg of acetylene at 20 ° C and a pressure of 760 mm Hg. of Art. 5.5 / 1.09 = 5.05 m 3.
TABLE. Comparative characteristics of acetylene, propane, and methylacetylene-allene fraction (IRF)
| Parameter | acetylene | propane | IAF |
| The sensitivity to impact, safety | unstable | stable | stable |
| Toxicity | minor | ||
| Explosive limits in air (%) | 2,2–81 | 2,0–9,5 | 3,4–10,8 |
| Explosive limit for oxygen (%) | 2,3–93 | 2,4–57 | 2,5–60 |
| Flame temperature (° C) | 3087 | 2526 | 2927 * |
| Reaction with conventional metals | avoid the alloys containing more than 70% of copper | minor restrictions | avoid the alloys containing more than 65-67% of copper |
| The tendency to kickback | significant | minor | minor |
| The rate of combustion in oxygen (m / s) | 6,10 | 3,72 | 4,70 |
| The gas density (kg / m 3 ) | 1,17 (при 0°С) 1,09 (при 20°С) | 2,02 (при 0°С) | 1,70 (при 0°С) * |
| The density of liquid at 15,6 ° C (kg / m 3 ) | – | 513 | 575 |
| The ratio of oxygen consumption to fuel gas (m 3 / m 3 ) in the normal flame | 1–1,2 | 3,50 | 2,3–2,5 |
| * - data "Naftan" plant "Polymir" (Novopolotsk, Belarus), a manufacturer of IAF | |||
See also:
gas welding
gas cutting
flame cutting
Welding materials:
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