Airco Close Coupled 4" Impeller LN2/LOX Pump - 3 HP, 30 GPM

What flow and head is this rated for, and at what NPSH?

This unit is rated for 30 gallons per minute. Head and NPSH are not specified in the listing. You'll need to ask the seller for the performance curve or nameplate data showing discharge head at rated flow and required net positive suction head, which varies significantly among close-coupled cryogenic pumps depending on impeller design and speed.

What seals, materials and drive does it have?

The listing specifies a 4" bronze impeller, wax-sealed design, and 3 horsepower motor in a close-coupled configuration. Bronze is typical for LN2 but less common for LOX due to copper compatibility concerns; confirm the specific bronze alloy and whether all wetted parts meet your oxygen service requirements if LOX use is intended.

What should I inspect on a used pump before buying?

Check impeller for erosion or cavitation damage, shaft runout, and bearing condition—cryogenic service causes thermal cycling that can fatigue bearings prematurely. Inspect the motor windings for moisture ingress from condensation, verify the wax seal integrity, and confirm all wetted materials if oxygen service is intended. If the pump ran LOX, verify oxygen cleaning documentation or plan for complete cleaning and passivation before use.