Texas Compressed Natural Gas (CNG) Delivery Truck Driver Practice Exam

Cylinders under a DOT exemption that require fire tests must be equipped with pressure relief devices. These devices are essential for the safe operation of compressed natural gas cylinders because they prevent the build-up of pressure that can occur when the cylinder is exposed to high temperatures, such as in a fire. When the temperature increases, the gas inside the cylinder expands, leading to increased pressure. If this pressure were to exceed the cylinder's design limits, it could result in catastrophic failure. The primary function of pressure relief devices is to release gas safely when the pressure reaches a specified threshold, thereby reducing the risk of explosion or rupture. Implementing these safety measures is critical in maintaining the integrity of the cylinder and ensuring the safety of both the driver and the surrounding environment. Alternatives like pressure sensors, automatic shut-off valves, or fire suppression systems, while important in their respective contexts, do not specifically address the need for pressure management in the event of a fire as effectively as pressure relief devices do.