What is a common indication that an acetylene cylinder is over-pressurized?

A common indication that an acetylene cylinder is over-pressurized is the release of the safety plug. The safety plug is designed to melt at a specific temperature, allowing gas to escape in order to prevent the cylinder from rupturing due to excessive pressure. When the internal pressure within the cylinder rises beyond safe limits, the safety plug activates to vent the gas, thereby reducing pressure and mitigating the risk of an explosion.

The presence of other signs, such as discoloration or hissing noises, might indicate various issues with the cylinder or its contents but do not directly relate to the specific concern of over-pressurization. Excessive temperature could be a contributing factor to increased pressure but is not a direct indicator like the safety plug's release. Understanding these operational safety features is crucial for handling acetylene cylinders correctly and ensuring safe working conditions.