The LO unloader maintains a setpoint pressure of which value at the farthest bearing?

• A. 15 PSIG
• B. 14.5 PSIG
• C. 10 PSIG
• D. 20 PSIG

Answer: (B)

The pressure at the farthest bearing is what the LO unloader regulates, because that point experiences the greatest drop from the pump to the bearing due to line resistance. Keeping the farthest bearing at a fixed 14.5 PSIG ensures there’s always a sufficient oil film there, even as flow and system conditions change, while leaving some headroom for normal pressure fluctuations elsewhere in the system. If the setpoint were higher, you’d risk overpressuring parts of the system or losing the ability to respond to changes; if it were lower, the furthest bearing could starve for lubrication. So 14.5 PSIG is chosen to balance reliable lubrication at the most distant point with safe, stable operation overall.