🔍 Key Concepts
• Function of a recirculating (minimum-flow/bypass) line on a centrifugal feed pump
• Behavior of turbine-driven feed pumps at low flow conditions (overheating, cavitation, stability)
• Normal functions of a DC heater (dearating/controlling temperature) versus what auxiliary lines are for
💭 Think About
• Ask yourself: When the boiler load is very low, what is happening to the flow through the feed pump, and why might that be a problem for the pump itself?
• Which part of the system (boiler drum, pump seals, condenser, or DC heater) most critically needs protection from low-flow or no-flow conditions?
• Does a recirculating line mainly control the boiler water level, provide sealing water, remove heat from a condenser, or protect the pump’s operating conditions?
✅ Before You Answer
• Verify what a minimum-flow or recirculation line on a centrifugal pump is designed to protect (the pump vs. the boiler vs. condenser).
• Check whether labyrinth packing on a turbine-driven feed pump is normally sealed by an external recirculating line from discharge, or by another source (steam, gland sealing system, etc.).
• Confirm the primary purpose of the DC heater (deaeration and heating of feedwater) and whether the recirc line’s main job is to control level, cooling, or pump operating flow.