Mechanical Systems (2022)
The engine shafts are supported by bearings. Some of them can support axial and radial loads. Other bearings are cylindrical roller bearings used only for radial loads. The bearings have to be stored in bearing sumps which are part of the oil system, and the oil has to be kept in different oil sumps within the system by the shaft. The engines normally have 2 and 3 shafts: HP, LP and IP shafts. The rotating parts (shafts and discs) are supported by bearings in oil sumps for proper lubrication.
Various types of seals provide sealing of oil areas; these are usually labyrinth seals, but carbon (nickel-graphite) seals can also be used in some places.
- The serviceability of the sealing surfaces (thermal spraying) and the tightness of the bearing housings (pressure test) are essential for perfect insulation.
- Furthermore, if parts are assembled with connectors, the fittings must be re-faced or replaced, as leaks outside the oil system can contaminate the airflow or cause a fire in the engine.