The maximum differential pressure setting allowed by NFPA 58 and UL listing for propane pump bypass vlave

• A. 75psi
• B. 125psi
• C. 150psi
• D. 200psi

Answer: (B)

The concept being tested is the maximum differential pressure at which a propane pump bypass valve is allowed to operate. NFPA 58, along with UL listings, sets this limit at 125 psi. That means the bypass valve is designed to open and relieve pressure once the pressure difference between the pump’s supply side and discharge side reaches 125 psi, preventing over-pressurization that could stress piping, fittings, or the tank and creating a hazardous condition.

Choosing a lower setting, such as 75 psi, would cause the valve to open too readily, leading to frequent bypassing and potential inefficiency or instability in the system. Choosing higher settings, like 150 or 200 psi, would exceed the listed maximum and could leave the system vulnerable to dangerous pressure levels before relief occurs. The 125 psi limit strikes a balance between protecting equipment and ensuring reliable operation within the safety standards.