Pressure relief valves must not be installed in what configuration?

Pressure relief valves are critical components in ensuring the safety of low-pressure systems by preventing overpressure conditions. Installing pressure relief valves in series is specifically discouraged because it can lead to a variety of issues that compromise the effectiveness and reliability of the system.

When pressure relief valves are arranged in series, the upstream valve must first open before the downstream valve can function. This configuration can result in the first valve being unable to relieve pressure effectively, particularly if it gets stuck or is obstructed, which defeats the purpose of having a pressure relief mechanism. Moreover, the pressure also has to build sufficiently high to open both valves, which may not always happen in rapid pressure spikes, leading to a dangerous situation.

In contrast, configurations such as parallel or combination installations are typically allowed because they ensure that multiple valves can operate independently. This independent operation means that if one valve does not function correctly, others can still relieve pressure, maintaining system integrity and safety. Thus, the emphasis on avoiding series installations stems from the need for reliability and safety in pressure relief systems.