Welding Certificates: Propane and Butane

Propane and butane - a mixture of two oil hydrocarbon gases, propane C 3 H 8 and butane C 4 H 10 . Propane-butane mixture in the gaseous state is a colorless, not poisonous, is heavier than air, has a strong odor of odorants - silnopahnuschih substances added to gas to detect possible leaks. With decreasing temperature and increasing pressure mixture becomes liquid.

Propane consists of propane C 3 H 8 with a mixture of propylene C 3 H 6 and is a colorless gas with a pungent odor of odorants.

Butane C 4 H 10 has a higher calorific value than propane, but has a higher temperature of the onset of gas formation (-0,5 ° C in butane and -42 ° C for propane). In this regard, at a temperature of -0,5 ° C lower than the selection of butane gas is not possible. A mixture containing butane from 5 to 30% (with a predominance of propane) has a high calorific value and can be used in cold climates with an ambient temperature to about -25 ° C.

Propane-butane mixture is obtained as a free natural gas production, oil refining and petroleum products.

Welded steel cylinders with propane (propane-butane) in accordance with GOST 15860-84, GOST 949-73 dyed red with the words "Propane" ("Propane-butane") in white. The gas pressure in the cylinder up to 1.6 MPa. In the evaporation of 1 kg of liquid propane produces about 530 liters of gas, the evaporation of 1 kg of liquid butane - about 460 liters of gas.

Hazards and safety precautions when working with propane-butane (according to GOST 20448-90):

LPG explosion and fire, they form explosive mixtures with air when the vapor content of the propane in the range of 2,1-9,5% 1,5-8,5% normal butane (by volume) at a pressure of 1 atm and a temperature of 15 to 20 ° C;
auto-ignition temperature of gases in the air at a pressure of 760 mm Hg. of Art.
Propane - 466 ° C;
normal butane - 405 ° C;
isobutane - 462 ° C;
in contact with the human body liquefied gases cause frostbite;
liquefied petroleum gases have on the body drug exposure;
at low concentrations of gases in the air for protection from oxygen starvation filter masks are used at high concentrations - insulated hose masks with forced clean air;
production facilities must be equipped with forced ventilation;
used in fire extinguishing agents such as foam or carbon dioxide extinguishers, dry sand, mist spray of water, steam, etc.

The use of propane-butane gas welding and cutting
Propane-butane mixtures are widely used as fuel gas for oxygen cutting . They are also available as substitutes for acetylene gas welding.

Propane and butane

Effective thermal capacity of the flame during the combustion of propane-butane in oxygen, even higher than that for acetylene. However, due to significantly lower the flame propagation velocity of these mixtures length of the cone of the flame is greatly increased and the concentration of the flame below. Under the temperature of the flame during the combustion of propane-butane mixtures as compared to acetylene.

TABLE. Comparative characteristics of combustible gases - propane, acetylene and methylacetylene-allene fraction (IRF)

Parameter	propane	acetylene	IAF
The sensitivity to impact, safety	stable	unstable	stable
Toxicity	minor
Explosive limits in air (%)	2,0–9,5	2,2–81	3,4–10,8
Explosive limit for oxygen (%)	2,4–57	2,3–93	2,5–60
Flame temperature (° C)	2526	3087	2927 *
Reaction with conventional metals	minor restrictions	avoid the alloys containing more than 70% of copper	avoid the alloys containing more than 65-67% of copper
The tendency to kickback	minor	significant	minor
The rate of combustion in oxygen (m / s)	3,72	6,10	4,70
The gas density (kg / m ³ )	2,02 (at 0°С)	1,17 (at 0°С)	1,70 (at 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	3,50	1–1,2	2,3–2,5
* - data "Naftan" plant "Polymir" (Republic of Belarus, Novopolotsk), a manufacturer of IAF