Acetylene (C2H2) is highly flammable gas (explosion limit 2.5%-82%), and its safe storage must strictly conform to the pressure vessel specification. According to GB 11638-2020 standard, the working pressure of the acetylene cylinder shall not exceed 1.52MPa, the material of the cylinder body is 16MnR steel, the wall thickness is ≥5.2mm, and the interior is filled with porous material (porosity 92%±2%) and acetone solvent (purity ≥99.5%), and the solvent volume is 40%-45% of the cylinder volume. Acetone loss should be refilled every 5 years (average volatilization rate per year 0.8%). For example, a 2021 United States Chemical Safety Board (CSB) report indicated that a welding plant used an old gas cylinder (produced in 2005) with porosity reduced to 85%, which resulted in an acetylene decomposition explosion with direct costs of $1.2 million.
Storage environment Temperature and ventilation need to be controlled. The temperature of the acetylene cylinder storage area should be ≤40℃, the relative humidity ≤70%, and the distance from the open fire or heat source should be ≥10 meters, and the ventilation frequency should be ≥12 times/hour. Eu ADR regulations require that trucks transporting welding gas acetylene be equipped with an explosion-proof temperature control system (temperature control accuracy ±2 ° C) and an acetylene concentration monitor (alarm point 1% volume concentration) in the cargo compartment. Take Linde Group’s warehouse in Germany for instance, its acetylene storage area uses explosion-proof wall (fire resistance limit ≥2 hours) and automatic spray system (response time ≤30 seconds), which successfully isolated the 2022 fire caused by short circuit and avoided the chain explosion hazard of 200 tons of acetylene cylinders.
Cylinder inspection and maintenance cycles have direct influences on safety. China’s “Gas cylinder Safety Technical Supervision Regulations” stipulates that acetylene cylinders shall be water pressure tested every three years (test pressure 3.0MPa, pressure holding time ≥3 minutes), and the cylinder body residual wall thickness (not less than 90% of the design value). According to Jiangsu Special Inspection Institute’s sampling statistics in 2023, the defect rate of the overdue gas cylinder is as high as 17.3% (crack, corrosion depth ≥0.5mm), while the failure rate of the regularly maintained gas cylinder is only 0.9%. Japanese JIS B 8241 standard requires that the leakage rate of the gas cylinder valve be monitored every month (helium mass spectrometry detection limit ≤1×10^-6 Pa·m³/s), and when the leakage quantity in one year exceeds 0.5%, the valve is forcibly replaced, with the related maintenance expense occupying about 15% of the total storage expense.
Standardization of process operation reduces risk. When storing the acetylene cylinder vertically, the inclination Angle should be ≤5°, and the shockproof ring (rubber hardness 70±5 Shore A) and bottle cap (impact strength ≥10J) should be utilized. United States OSHA statistics show that acetylene leakage accidents caused by cylinder dumping accounted for 23% of the annual industrial gas accidents in 2022, and 80% of the accidents were caused by the neglect of mounting fixed supports (bearing capacity ≥2 times the weight of the cylinder). By introducing an automatic handling robot (positioning accuracy ±1mm), an Australian shipyard has reduced the possibility of gas cylinder collisions from 4.2 to 0.3 times a year, and by 40% improved storage efficiency. In addition, the process of opening bottles is carried out with a special wrench (torque restricted to 25-35N·m) to prevent stem breakage leading to high pressure injection (flow rate as high as 300m/s).
Emergency response systems shall deal with the whole life cycle. Acetylene storage room shall be equipped with dry powder fire extinguisher (not less than fire extinguishing grade 55B) and emergency isolation valve (operation time ≤2 seconds); gas detector (detection range 0-100%LEL) shall be installed every 100 cubic meters of space. In the 2020 Ulsan chemical plant explosion accident in South Korea, due to the detector calibration error (the actual concentration has reached 120% of the lower explosive limit, but the indicated value is only 85%), the emergency isolation system was delayed, and eventually 3 tons of acetylene exploded. British standard BS EN 1127-1 recommends quarterly leak simulation, and the figures are that companies’ emergency response time can be reduced to 90 seconds (240 seconds is the industry average) and accident-related losses can be reduced by 65%.
Innovations in technology make it easier for storage security to be improved. French Air Liquide’s intelligent gas cylinder (integrated pressure-temperature-concentration three-parameter sensor) transmits data to the cloud platform in real time through NB-IoT (sampling frequency 1 time/minute), which can trigger the automatic pressure relief valve (opening pressure 1.8MPa) at the initial stage of acetylene decomposition reaction (temperature rise rate ≥5℃/min). They will test this technology in Europe in 2023, reducing the accident rate of acetylene storage to 0.02 times per thousand bottles per year, a 15 times safety factor improvement compared to traditional methods. At the same time, the application of phase change storage materials (such as paraffin-graphite composite) can keep the surface temperature of the gas cylinder consistently below 32 ° C in the 40 ° C environment, and extend the service time of acetone by about 20%.