The correct answer is B because a pressure reading between the rupture disc and relief valve—where it should normally be zero—indicates that the rupture disc has likely failed or is leaking . This creates a serious hazard because the pressure relief valve (PRV) may no longer function as intended , especially if backpressure builds up or if the system configuration compromises its ability to relieve safely. This condition can lead to loss of overpressure protection , increasing the risk of vessel rupture or explosion.

From a CCPS RBPS perspective, several elements are implicated. Mechanical Integrity is central, as the rupture disc may not have been properly inspected, maintained, or replaced. Operating Procedures and Training and Performance Assurance are also relevant, as operators must recognize abnormal readings and respond appropriately. Hazard Identification and Risk Analysis (HIRA) should have considered failure modes such as rupture disc leakage and its impact on relief system performance. Additionally, Management of Change (MOC) could be involved if modifications or replacements were made without proper review.

This scenario highlights how degradation or failure of protective devices, combined with gaps in multiple RBPS elements, can undermine critical safety layers and lead to potentially catastrophic consequences.