Liquid Oxygen Pumps

Model BNCP-67-000 Liquid Oxygen Pump

Liquid oxygen pumps must be designed with careful consideration as LOX is not particularly compatible with many materials typically used in cryogenic machines. Leakage must also be carefully controlled or reduced to very low helium leak rates as oxygen poses a fire hazard. Barber-Nichols’ typical hermetically sealed, long shaft pumps will not work with oxygen as motor materials and our standard high-speed bearing grease are not LOX compatible. BNI employs canned motors, magnetic couplings and advanced seal technologies in the liquid oxygen pumps it produces.

While liquid oxygen’s standard temperature of 90 K is not especially cold in the cryogenic world, it is still often desirable to reduce the conducted heat input to the cryogen.  BNI modified its long shaft pumps to include magnetic couplings to allow for use with liquid oxygen and other cryogens that must be kept ultra-clean. The liquid oxygen pump shown above includes a magnetic coupling and BNI developed this pump for circulating LOX in a laser system. The magnetic coupling isolates the motor and its bearings from the oxygen by the use of a barrier can. The magnetic torque is transmitted from the motor on the outside of this barrier can to the impeller shaft on the inside. All of the materials in contact with LOX are compatible and well-proven in this application.

Model BNCP-45-000 Liquid Oxygen Pump

BNI also made canned motor pumps for low-power liquid oxygen applications. The diminutive pump shown at left was delivered to NASA for testing on bi-propellant thrusters (for the replacement of hydrazine). It has a brushless DC motor direct-driving a partial emission pump operating at 28 VDC. The canned motor is actually overhung with a small extended shaft riding on self-lubricating ball bearings compatible with LOX.

NASA Liquid Oxygen Pump

Launch vehicles require large quantities of cryogenic propellants which must be transferred from storage tanks on the ground into the tanks on the vehicle. Accomplishing this quickly is enabled by large cryogenic pumps such as Barber-Nichols model BNCP-65-000 LOX pump, capable of flowing 4500 l/min (1200 GPM).

Case Study

The liquid oxygen pump shown at right was developed for large rocket loading at NASA.  It utilizes an innovative dual-seal arrangement with gas lift-off and a dynamic seal with purge gas that prevents any leakage during operation.  It is rated for approximately 200 hp and pumps up to 1,200 GPM at 185 psi.  The pump utilizes an inducer that minimizes the necessary Net Positive Suction Head (NPSH) and it employs a maintenance-ready design that allows the motor and all pump elements to be retracted from the housing which can remain attached to the system.