The hottest pressure vessel and fire and explosion

2022-09-29
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Pressure vessel and fire and explosion prevention

pressure vessel explosion accident refers to the accident that the pressure is instantly reduced to the external atmospheric pressure due to the rupture of the pressure vessel in use or in the test; It refers to the process that a substance rapidly changes from one state to another, and releases a large amount of energy in the form of mechanical energy in an instant. The explosion of pressure vessels can be divided into physical explosion and chemical explosion

when the working medium is filled into the pressure vessel or the chemical reaction, heat exchange and other processes are carried out in the vessel, the working medium is constrained by the vessel barrel, that is, a force is applied to the shell, and the pressure vessel can work normally when the force does not exceed the acting stress range of the shell. However, when the pressure vessel breaks down for various reasons, the high-pressure gas in the vessel breaks through the constraints of the vessel wall, expands rapidly in a very short time, and releases internal energy at a very high speed, which is a physical explosion

if the pressure vessel whose working medium is combustible gas breaks, a large amount of combustible gas will be released and quickly mixed with air. When the mixing ratio reaches a certain concentration, an explosive gas mixture is formed. Static electricity generated by the high-speed outflow of gas or sparks generated by the impact of debris provide conditions for detonation. As a result, after the container burst, a chemical explosion occurred soon, which is commonly referred to as the second explosion

these two explosions often occur successively, and the interval between them is very short. The two explosions are becoming a hot research and development topic in the world. Both explosions release energy, and the energy of the second chemical explosion is often much greater than that of the gas expansion of the first explosion. The combustion of flammable medium in pressure vessel can cause explosion or detonation, which can be carried out inside the pressure vessel or in the space outside the vessel. The combustion reaction of flammable medium is carried out at a very high speed, and the shock wave of local overpressure passes through the pipeline or equipment, which is called detonation. The difference between detonation and explosion is that detonation propagates at supersonic speed and causes a directional shock wave, and its peak pressure is sometimes about 20 times greater than the peak pressure of the shock wave formed by explosion

(1) overpressure in use. Due to violation of operating procedures, operational errors or other reasons, the pressure in the container rises above the maximum acting pressure, and the container is not equipped with a safety pressure relief device or the device is ineffective, until the container is cracked due to excessive plastic deformation

(2) overfilling. When filling liquefied gas, due to negligence of operation, metering error or other characteristic parameters: ring stiffness: excessive filling caused by placing the pipe sample. Once the ambient temperature is higher than the filling temperature, the volume of liquefied gas in the container expands, causing great pressure, resulting in the rupture of the impactor

(3) improper design, manufacturing and installation. Such as wrong design, minor defects left during welding, wrong material selection for manufacturing containers, cracks in materials, etc

(4) poor maintenance. The vessel has been idle for a long time without effective anti-corrosion measures, resulting in large-area corrosion and thinning of the vessel wall, resulting in cracks in the vessel. Poor maintenance quality and incomplete elimination of defects

(5) gas cylinders are misinstalled and misused. There are many kinds of gases contained in gas cylinders, and the properties of various gases are different. If the two kinds of gases are mixed, chemical explosion may occur, such as oxygen and hydrogen. This kind of accident mostly occurs because there is no paint color and mark on the gas cylinder or the operator does not pay attention to the paint color and mark

(6) due to the poor working conditions of the boiler. At high temperature and high pressure, some of its metal components are always affected by flue gas, and its error is generally negative difference and steam water medium; Medium brush and erosion, therefore, the metal components of the boiler are prone to corrosion, wear, leakage, deformation and cracks, which buried the hidden danger of explosion

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