🔍 Key Concepts

• Positive-displacement lube oil pump operation and how discharge pressure is created • Typical causes of loss of discharge pressure on a lube oil system • Difference between conditions that cause low/no pressure vs. conditions that cause high pressure or overflow

💭 Think About

• For each choice, ask: Would this condition tend to reduce discharge pressure, increase it, or have little effect? • Think about where the bypass valve, gravity tank, discharge strainer, and shaft packing gland are located relative to the pump suction and discharge. • Which option would most directly allow oil to escape or fail to be forced into the discharge line, leading to low or no pressure at the outlet?

✅ Before You Answer

• Verify which situations would normally cause low discharge pressure (e.g., internal or external leakage, loss of suction, open bypass). • Check whether any option would actually create higher pressure or overflow, which would be the opposite of the symptom in the question. • Confirm which component, if improperly set or maintained, would let the pump circulate oil without building pressure in the discharge line.