At what temperature is the fusible plug in an acetylene cylinder designed to melt?

• A. 100 degrees Celsius
• B. 50 degrees Celsius
• C. 200 degrees Celsius
• D. 150 degrees Celsius

Answer: (A)

The safety device in an acetylene cylinder is a fusible plug that melts at a relatively low temperature to vent gas and prevent a dangerous rupture if the cylinder overheats. It is designed to melt at about 100°C, so when heat from a fire or high ambient temperature raises the cylinder to that point, the plug softens and creates an opening for gas to escape safely rather than building up pressure. If it melted at 50°C, it would vent too easily during normal conditions; if it waited until 150°C or 200°C, the cylinder could overheat and fail before relief occurs. Thus 100°C is the appropriate trigger temperature for this safety feature.