In a low-pressure system, the rupture disk vents at which psig?

• A. 10 psig
• B. 12 psig
• C. 20 psig
• D. 15 psig

Answer: (D)

Rupture disks are designed to relieve a system only when the pressure reaches a specific burst pressure, which is chosen to protect the vessel without venting during normal operation. In a low‑pressure system, you want that burst pressure just above the usual operating range so the disk stays intact under normal conditions but vents if pressure climbs toward the safe limit. If normal operation sits around 10–12 psig, a disk set to 15 psig provides the needed margin: it won’t vent during normal fluctuations, yet will rupture to relieve pressure before the system exceeds safe levels. A higher value like 20 psig would vent too late for typical low‑pressure protection, while a lower value such as 10 or 12 psig would vent during normal operation. So 15 psig is the appropriate choice.