What should always be done before performing maintenance on a pressure piping system?

Before performing maintenance on a pressure piping system, it is essential to isolate and depressurize the system. This step is crucial because it ensures the safety of the personnel involved in the maintenance process. By isolating the system, you effectively eliminate any risk of unintended movement of fluids or gases that could lead to accidents or injuries.

Depressurizing the system removes the stored energy that could otherwise cause rapid fluid release or even a potential explosion if a rupture occurs during maintenance. This action helps to create a safe working environment, allowing mechanics to inspect and repair the system without the associated risks that come from working on a pressurized system.

Other options, such as increasing the pressure or opening all valves, could create dangerous conditions or lead to system failure. Notifying personnel of potential hazards, while important, does not directly address the immediate safety measures that need to be taken before beginning work.