What is installed on propane cylinders to allow excess pressure to escape?

The relief valve is a critical safety component installed on propane cylinders designed to prevent dangerous overpressure situations. When the internal pressure of the cylinder exceeds a predetermined limit, the relief valve activates, releasing excess gas to the atmosphere. This mechanism is vital for maintaining safe operating conditions, as it helps to avoid potential hazards such as cylinder rupture or explosion due to excessive pressure buildup.

The relief valve functions by automatically venting propane gas when the pressure rises to a specific threshold. It ensures that the cylinder remains within safe limits during the various temperature and pressure fluctuations that can occur, especially in different environmental conditions. By allowing the safe release of pressure, the relief valve effectively protects both the equipment and individuals handling or in proximity to the propane cylinder.

In contrast, the other options such as the safety cap, pressure gauge, and locking mechanism do serve important functions but do not play a role in pressure regulation. The safety cap is used primarily to protect the valve from physical damage and contaminants. The pressure gauge measures the internal pressure but does not control or relieve it. The locking mechanism secures the cylinder to prevent unauthorized access but does not impact pressure management. Thus, the relief valve is essential for ensuring the safe operation of propane cylinders.