In service, there is a space between a shaft and a self-lubricating PM bearing that contains an oil film when the bearing is operating properly. In the event the oil film is disrupted or fails to form the bearing will exhibit increased wear and possibly fail. Therefore the ability for oil to flow through the porosity of a PM bearing is critical to the performance of the bearing.

The porosity of the bearing must be open to the surface and interconnected within the bearing. This allows the oil in a self-lubricating PM bearing to flow during operation to the space between the bearing and the shaft to form an oil film and protect the shaft from wear.

The ability of a gas to flow through the bearing reflects the openness and interconnected properties of the porosity in the bearing.

Data from this test can be used as an internal quality tool and can be reported to buyers of bearings.

A number of other factors also affect the performance of the bearing and the movement of oil; factors such as the oil viscosity, operating temperature, load, shaft speed, surface area, surface finishes and others. This test provides information on only one property and cannot be the sole consideration in the design and testing of a bearing application.