What system component ensures that the tank does not overfill?

The component that ensures the tank does not overfill is the automatic shutoff valve. This device is designed to stop the flow of fuel when the tank reaches a predetermined level, thereby preventing spillages and potential environmental hazards resulting from tank overfilling. The automatic shutoff valve operates in conjunction with other systems to monitor the level of fuel in the tank continuously. When the target level is met, it triggers a closure mechanism that halts further incoming fuel, making it a critical safety feature in fuel-oil piping and storage systems.

While other components such as a pressure relief valve can manage pressure conditions within the system and are essential for safety, their primary function is not to prevent overfilling. A manual pump is used to facilitate the transfer of fuel but does not inherently prevent overfilling either, as it requires operator action, which may be subject to error. Lastly, a refill indicator serves as a visual tool to alert operators to the fuel level but does not actively stop the flow of fuel. Thus, the automatic shutoff valve serves the pivotal function of automatically preventing overfilling, reinforcing proper safety protocols in fuel storage systems.