There are several types of pressure relief valves available, including spring-loaded valves, pilot-operated valves, and rupture discs. Spring-loaded valves are the most common type and are suitable for most applications. Pilot-operated valves, on the other hand, are typically used for high-flow applications or where a high degree of accuracy is required. Rupture discs are used in applications where a rapid release of pressure is required, such as in fire suppression systems.