Fuel transfer pump

Abstract

An improved fuel transfer pump is provided for use in transferring fuel within fuel tanks such as fuel tanks within an aircraft. The pump comprises a relatively compact and substantially modular pump assembly including a rotatably driven impeller carried at one end of an impeller shaft for relatively high flow transfer of fuel from a fuel inlet to a fuel outlet. The impeller shaft is rotatably supported within a pump housing by sets of angular contact bearings preloaded in a direction to prevent eccentric run-out or excessive axial end play in response to bearing wear over the operating life of the pump. In addition, an hydraulic motor is mounted within the pump housing axially between the bearing sets and is driven by a source of hydraulic fluid for rotatably driving the impeller shaft. Inherent leakage of hydraulic fluid from the motor is circulated to and past the bearing sets and related shaft seals for cooling these components, thereby preventing pump overheating and possible ignition of fuel vapors during a dry run condition. A seal assembly is mounted on the impeller shaft for substantially preventing leakage of hydraulic fluid into a fuel flow path and vice versa. The seal assembly includes a pair of carbon seals rotatably mounted on the impeller shaft on opposite sides of an internally ported stationary seal ring.