What is a key requirement for series PRV installation?

A critical aspect of installing series pressure reducing valves (PRV) is maintaining a specific turn-down ratio, which refers to the range of pressure reduction these valves can effectively manage. This isn't just about reducing pressure; it’s essential for the efficiency and reliability of the system. If the turn-down ratio is not maintained, especially at a level like 10:1, it can lead to inadequate pressure reduction and result in system instability.

Additionally, if the pressure differential is out of range, it undermines the function of the PRV system, leading to potential overpressure or performance issues. The requirement for a specific turn-down ratio helps ensure that the valves can respond appropriately under varying load conditions, maintaining effective operation throughout the valves' operational range.

While the other options touch on elements that could be relevant in different contexts, they do not encapsulate the fundamental technical requirement for series PRV installation as effectively as the necessity for maintaining an appropriate turn-down ratio while managing pressure differentials. Therefore, the focus on the turn-down ratio and pressure differential as a key requirement aligns directly with the operational effectiveness of series PRVs.