What is the activation pressure of the built-in relief valve for the fuel service pumps?

• A. 150 PSIG
• B. 110 PSIG
• C. 130 PSIG
• D. 135 PSIG

Answer: (C)

Activation pressure is the point at which the built-in relief valve opens to protect the fuel service pump circuit from overpressure. It’s set above the normal operating discharge pressure so the pump can build the required head for service, but low enough to vent excess pressure before pipes, fittings, or the pump itself are stressed.

For the fuel service pumps, the relief opens at 130 PSIG. This value provides a safe margin above typical operating pressure, ensuring normal flow is maintained, while still preventing damage if pressure spikes occur. If it were set higher, like 150 PSIG, pressure could climb higher before relief occurs, risking equipment damage. If set lower, such as 110 PSIG, the valve would relieve too often during normal operation, causing instability in pressure and flow. A setting around 135 PSIG is close but may not match the system’s protective requirement, whereas 130 PSIG aligns with the designed protection level for these pumps.