Prevention of acetylene bottle explosion accidents for gas welding and gas cutting

Acetylene is a very dangerous gas, but it is widely used in industry. Accidents may occur accidentally. The following is a summary of the knowledge of acetylene cylinders for everyone to learn.
       First, acetylene gas
       Acetylene (C2H2), alias calcium carbide gas, serial number 2629, CAS number 74-86-2, class 2.1 colorless and odorless flammable gas, lower explosion limit % (v/v): 2.1, upper explosion limit % (v/v 003mj。 In the air, the minimum ignition energy of acetylene is 0.019mj, and in oxygen, as long as 0. 003mj. The mixed gas of acetylene and air is easy to cause detonation, the detonation speed can reach 2200m/s, and the maximum explosion pressure can reach 58.8MPa. The temperature of the product when acetylene decomposes and blasts can reach 3100 °C. Acetylene and oxygen burn to generate heat, and the flame temperature is as high as 3,500 °C. It is more dangerous than hydrogen and is extremely flammable and explosive. According to the "Dangerous Chemicals Major Hazard Source Identification" (GB18298), the critical amount of acetylene is 1 ton. Calculated according to 40L per bottle, about 400 bottles constitute a major source of danger in warehouses or production sites.
       It can be mixed with air or oxygen to form an explosive mixture. In case of ignition, high temperature objects, static electricity, radiation and other ignition sources, it is easy to cause combustion and explosion. Contact with oxidizing agents will react violently. Contact with fluorine, chlorine, etc. will cause a violent chemical reaction. It can generate explosive substances with compounds such as copper, silver, and mercury. Under certain conditions of temperature and pressure, pure acetylene also undergoes its own direct decomposition explosion and its polymer decomposition explosion.
       Since acetylene is very dangerous, it has to be dissolved in a special gas cylinder containing acetone for safety.
      
       Second, acetylene bottle
       The acetylene bottle used for gas welding and gas cutting is a steel welding gas cylinder, which is a special steel cylinder for dissolving acetylene.
       The bottle is solid and has a porous filler. The filler has a large number of capillary pores. The solvent acetone is filled in the capillary pores, and the acetylene gas is dissolved in the acetone in the capillary pores. Therefore, the acetylene is dissolved and the package gas cylinder is It is called a dissolved acetylene cylinder.
       The top of the bottle has a bottle valve and a bottle cap. The surface of the bottle is painted white, and the word "acetylene" is written in red paint. The acetylene bottle valve is a valve for opening and closing acetylene. The valve body is made of low carbon steel. It must be opened and closed with a square hole socket wrench. The counterclockwise rotation is open and the clockwise rotation is closed. The specifications of acetylene bottles are 25, 40, 50, 60L, etc., generally 40L.
       The acetylene bottle shoulder is designed with a fusible alloy plug, which is shaped like a nut with a through hole in the middle, and the hole is filled with an alloy of low-melting palladium and rhodium.
       When the cylinder is used for tempering, once the temperature in the bottle reaches 100±5°C°, the fusible alloy in the fusible plug melts, opens the passage, and the acetylene gas is discharged from the hole of the filled fusible alloy. Relieve the pressure, reduce the temperature, and ensure the safety of the cylinder. This is a safety device that the acetylene bottle must have. In addition, a fusible alloy safety device is also designed on the bottle valve of the acetylene bottle.
   

       Third, the cause of the acetylene bottle on fire
       There are several reasons for the direct explosion of acetylene bottles:
       The porous filler of the acetylene bottle sinks, and a net space appears, so that part of the gaseous acetylene is in a high pressure state.
       When filling, the acetone is not filled as required, and the acetone in the bottle is seriously deficient; when the acetylene bottle is placed horizontally, or acetone is used in large quantities, the acetone flows out.
       The gas cylinder material does not meet the requirements, or manufacturing defects; the inner and outer surfaces of the gas cylinder are corroded, the wall of the bottle is thinned, the strength is decreased; the acetylene bottle valve leaks.
       The gas cylinder is hit and impacted during transportation and handling, causing mechanical damage; when the gas cylinder is transported and loaded, it falls, falls, and rolls from a height, causing a violent collision impact.
       Acetylene is exposed or baked during use and the temperature is outside the allowable range (the bottle is not allowed to exceed 40 °C).
       Tempering occurs during gas welding or gas cutting, and the flame enters the bottle.
       When the filling volume of the acetylene bottle and the filling pressure exceed the limit, the acetylene will also cause a combustion explosion.
     
        4. What should I pay attention to when operating, storing and transporting?
       1. operating
       When using dissolved acetylene, control the flow rate to prevent static electricity from accumulating.
       It is forbidden to use mechanical electrical equipment and tools that are prone to sparks in the operating area.
       When dissolving the acetylene cylinder, the tempering arrester must be configured.
       Use a special valve wrench that does not ignite, and use it in an upright position.
       When deflated, the pressure shall not exceed 0.15MPa, and the flow rate shall not exceed 0.6m3/bottle.h. The gas in the bottle is strictly forbidden. The residual pressure is not less than 0.05MPa. Close the bottle valve after use.
       It is strictly forbidden to operate acetylene gas in case of leakage. At the time of acceptance, attention should be paid to the name of the product. Pay attention to the date of regular inspection. Dissolved acetylene cylinders shall be inspected periodically every three years. The cylinders for over-time inspection shall be promptly sent for inspection. Lightly load and unload during handling to prevent damage to cylinders and accessories. Operators must be specially trained to strictly follow the safe use of hazardous chemicals.
       When the gas cylinder is used, the external inspection is first carried out. The focus of the inspection is whether the bottle valve, the take-up thread and the pressure reducer are defective.
       When using neutral, there should be anti-dumping measures; it is strictly forbidden to knock or collide; the gas cylinder in the bottle should not be used up, and the valve should be opened slowly.
       Cylinders must be inspected periodically.
       Use the gas bottle bottom at the same working position as the electric welding operation to prevent thermal insulation of the cylinder.
       2. store
       Acetylene is usually dissolved in a solvent (acetone) and stored in the pores of the porous filler in the cylinder (ie, stored in a dissolved acetylene cylinder). Store in a cool, ventilated warehouse.
       The warehouse temperature should not exceed 30 °C. Keep away from fire, heat and direct sunlight. It should be stored separately from halogens, oxidants, etc. such as oxygen, compressed air, and chlorine.
       The lighting and ventilation facilities in the warehouse should be explosion-proof, and the switch should be placed outside the warehouse as much as possible.
       Equipped with the corresponding variety and quantity of fire-fighting equipment, set the fire hydrant.
       Acetylene bottles that have been in stock for more than three years, whether empty or full, should be sent to a professional inspection unit for inspection.
       3. transport
       Vehicles that transport dissolved acetylene cylinders should have warning signs and fire-fighting equipment. Flame-extinguishing devices should be installed at the exhaust vents. The transport personnel should have a qualification certificate.
       When acetylene bottles are shipped, they should be properly fixed, horizontally discharged, and the head facing one side, and must not exceed the height of the compartment; in the summer, there should be shading facilities to prevent exposure and transport in the evening.
       It is strictly forbidden to transport acetylene gas in the event of a leak. It is strictly forbidden to transport with oxygen cylinders, chlorine cylinders and oxidizers.
       When carrying the gas cylinder, it must be equipped with a safety helmet and a shock-proof ring; it should be lightly loaded and lightly unloaded, and it is strictly prohibited to throw or touch; the transportation means should have a safety mark; in the summer, there should be a sunshade; no fireworks; no flammable or explosive substances Transport together.

       Fives. How to extinguish fire and emergency?
       1. Extinguishing
       Close the valve and cut off the air supply. Spray the water to cool the container and, if possible, move the container from the fire to the open space. Extinguishing agents are water spray, foam, carbon dioxide, dry powder, and the like.
       If the air source cannot be cut off immediately, it is not allowed to extinguish the flame of the leaking gas to prevent tempering and avoid a more serious explosion hazard. It is forbidden to extinguish the fire with an alkyl halide fire extinguishing agent such as carbon tetrachloride.
       Bring the fire container and dissolve the acetylene gas cylinder. After the fire extinguishing, continue to use water to cool to the normal ambient temperature (≤40 °C).
       2. Emergency
       Rapid evacuation of personnel from the contaminated area to the upwind environment is strictly controlled.
       It is recommended that emergency personnel wear self-contained positive pressure breathing apparatus and wear fire protective clothing.
       Cut off the fire source; cut off the leaking gas source as much as possible; reasonably ventilate and accelerate the diffusion; dilute and dissolve by spray water.
       If possible, use the explosion-proof exhaust fan to the open air or install the appropriate nozzle to burn it.
       Leakage at the joint of the dissolved acetylene cylinder clamp, etc., can close the bottle valve and replace the gasket for disposal.
       Gas leaking containers and gas cylinders should be properly disposed of. It is strictly forbidden for users to weld and arbitrarily beat them. It should be sent to a professional inspection unit for repair and then used for inspection.

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