If Dewar bottles are not handled properly, there is a possibility of fire and explosion due to external factors during welding and cutting operations. The occurrence of overturning and explosion can be classified into the following situations:

1. Situation 1: Combustible gases, oils, or other flammable substances present in the workpiece or the container being welded (cut) can be ignited by the high temperature generated during the process. If the instant release of energy is not promptly dissipated, an explosion can occur. To prevent such explosions in Dewar bottles, the following measures can be taken:

• Welding (cutting) operations are prohibited on workpieces that contain pressurized liquids, water, or electricity.
• Welding (cutting) operations are prohibited on the surface of Dewar bottles if flammable materials are not removed.
• Welding (cutting) operations are prohibited on containers that have residual combustible materials or on containers with unclear internal media.
• Welding (cutting) operations are prohibited on oil pipelines unless they are completely separated from the oil system and thoroughly cleaned.

2. Situation 2: Fire can occur when there are combustible materials in the vicinity of the welding (cutting) operation, and the open flame ignites them. Precautionary measures include:

• Prohibition of welding (cutting) operations in areas with combustible materials.
• Elimination of combustible materials around the welding (cutting) operation or implementation of reliable isolation measures.
• After the welding (cutting) operation, the site should be cleaned, and the personnel can evacuate only after ensuring that there are no ignition sources.

3. Situation 3: Fire and explosion can occur from welding (cutting) gas cylinders. The reasons for Dewar bottle explosions include:

• The material, structure, or manufacturing process of the Dewar bottle does not meet safety requirements, such as material brittleness, severe corrosion, uneven thickness, or interlayers.
• Improper storage and use, such as exposure to sunlight, open flames, or heat radiation, causing an increase in gas temperature and pressure beyond the rupture disk’s designated value, resulting in explosion.
• Impact from falling or collision during transportation.
• Rapid gas release causing static sparks when passing through valves.
• Presence of grease on the nozzle of oxygen cylinders.
• Incorrect gas filling in Dewar bottles.
• Settlement of filler material in acetylene cylinders, creating void spaces.
• Acetone leakage when acetylene cylinders are placed upside down.

To prevent these explosions, the following measures can be taken for Dewar bottles:

• Shock prevention: Dewar bottles should avoid severe vibration and impact during handling, storage, and use. The bottle valve should be protected with a bottle cap to prevent valve breakage, and at least two shock-absorbing rubber rings should be used for each bottle. Vehicles transporting gas cylinders and the ground for loading/unloading should be covered with rubber mats to reduce impact.
• Heat prevention: Dewar bottles should always be kept away from heat sources, open flames, and flammable materials. Sunshades should be provided in summer to prevent direct sunlight exposure.
• The gas inside the bottle should not be completely exhausted.
• When the pressure of the Dewar bottle drops to 0.1-0.2 Pa, usage should be stopped, and the valve should be closed to prevent the reverse flow of flammable gas or air into the bottle due to lower pressure inside than the external pressure.
• Before use, inspect the gas cylinder and equipment: Focus on checking the bottle valve, inspection period, bottle color, regulator, welding (cutting) tools, and prohibit the use of those that do not meet the requirements.
• Keep the valve and regulator clean, free from grease and other contaminants.