Fire insurance and requirements for the hottest ga

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Fire risk and requirements of gas welding and gas cutting

common gas welding and gas cutting equipment consists of acetylene cylinder, oxygen cylinder and welding (cutting) torch. The energy used for gas welding and gas cutting is combustible gas, which is also filled in the pressure vessel, so the equipment itself has great fire and explosion risks. During welding and cutting operations, molten slag with high temperature and heat splashes everywhere, which is easy to ignite the surrounding combustibles, and also contacts many flammable, combustible and explosive substances, as well as various pressure vessels and pipelines. Therefore, in various welding and cutting operations, gas welding and gas cutting have the greatest fire risk

I. concept

gas welding is a fusion welding method that uses the flame of mixed combustion of combustible gas and oxygen to heat metal materials. The commonly used combustible gases for gas welding include acetylene and propane, as well as hydrogen, natural gas, coal gas and liquefied petroleum gas. The temperature produced by the combustion of these combustible gases with oxygen is as high as 2000 ~ 3000 ℃

gas cutting is a processing method that uses the flame of mixed combustion of combustible gas and oxygen to heat the metal to the combustion point, and then burns violently in the oxygen jet to separate the metal. The combustible gases used for gas cutting mainly include acetylene, propane and hydrogen

II. Equipment

1. Fire protection requirements for acetylene cylinders

(1) acetylene

acetylene (C2H2) is a colorless gas. Therefore, this small signal must be amplified by an amplifier. The specific gravity is 0.9, the melting point is -81.5 ℃, its boiling point is -83.6 ℃, the spontaneous combustion point is 335 ℃, the critical temperature is 36 ℃, the critical pressure is 62kg, and the explosion limit is 2.5 ~ 82%. Its chemical properties are extremely unstable and it is an unsaturated hydrocarbon. It is lighter than air. Industrial acetylene contains phosphine (below 0.06%) and hydrogen sulfide (below 0.1%), so it has a special odor. Acetylene will burn and explode under the following conditions:

when the temperature of acetylene reaches 300 ~ 450 ℃ or the pressure exceeds 0.15 MPa, acetylene molecules can generate polymerization and heat, causing spontaneous combustion. When the temperature exceeds 580 ℃ and the pressure exceeds 0.15 MPa, an explosion will occur. The 10000 ton anode material project mentioned above has not yet formed a range of production capacity

after long-term contact between acetylene and copper and silver, explosive compounds acetylene copper and acetylene silver will be generated. When subjected to severe vibration or when the temperature reaches 110 ℃, the electronic universal testing machine adopts the design of microcomputer controlled electro-hydraulic servo valve loading and manual hydraulic loading, and the main body and control frame are separated to 120 ℃

when the phosphine content in acetylene exceeds 0.15%, it can cause spontaneous combustion

when the content of acetylene in the air is 2.5% ~ 82%, it will explode when contacting with open flame. When acetylene is mixed with oxygen, when the acetylene content (calculated by volume) reaches 2.8 ~ 93%, it will explode in contact with open fire. This kind of explosion is very powerful. It is 10 times more powerful than acetylene mixed with air

A team led by researchers from Cornell University to develop new materials

(2) acetylene cylinder

acetylene cylinder is filled with microporous solid porous filler and acetone, acetylene is loaded into the cylinder under the pressure of 1.52mpa and dissolved in acetone, while acetone is adsorbed in the filler with micropores, so the risk of acetylene explosion in acetylene cylinder is much smaller

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