Explain the purpose of a 'rupture disc' in a high-pressure piping system.

The purpose of a rupture disc in a high-pressure piping system is to provide overpressure protection. It is a non-reclosing pressure relief device that is designed to burst at a predetermined pressure, providing a full and immediate release of pressure to prevent catastrophic failure of the system. Unlike pressure relief valves, which can reclose after relieving excess pressure, a rupture disc provides a one-time relief. It is typically used as a last line of defense against overpressure situations that might arise from equipment malfunction, fire, or other unexpected events. Rupture discs are commonly installed in systems containing hazardous or toxic fluids, where a leak from a relief valve could be dangerous. When the pressure in the system exceeds the rupture disc's burst pressure, the disc ruptures, creating a large opening that allows the fluid to vent to a safe location, such as a flare system or a containment vessel. The rupture disc is designed to fail reliably and predictably at its rated burst pressure, even under varying temperature conditions. It is a simple and reliable device that provides a cost-effective means of overpressure protection in high-pressure systems.