Final answer:
Compressed gas cylinders must have a pressure relief device to avoid rupture due to increased pressure from high temperatures. These relief devices are critical for safety, allowing containers to release excess pressure, and prevent accidents such as bursting or explosion.
Step-by-step explanation:
Compressed gas containers shall have a pressure relief device installed to prevent the rupture of a cylinder when inadvertently exposed to fire or high temperatures. When gas is stored at high pressure, such as the example of gas stored at 200 atmospheres, it is crucial to ensure safety measures are in place to avoid container failure due to increased pressure from elevated temperatures. In the event of a fire, as the cylinder heats up, the gas inside expands, and so does the pressure.
Considering a safety factor of 2, the container is designed to not fail until the reached pressure is around 400 atmospheres. Without a pressure relief device, the container could be at risk of rupturing, which is why these devices are essential to safely release gas to avoid a pressure increase beyond the container's capacity. This is also why some containers have air gaps to allow for expansion and contraction, preventing undue stress on the container walls.
It is important to remember that both liquids and solids resist being compressed with extremely large forces. So, to avoid the risk of the container bursting under high pressure, which could be more than enough to rupture a thin sheet metal container, the pressure relief device acts as a critical safety mechanism.