Exam Question

### (a) Importance of Measuring Bearing Clearances (4 Marks)
The measurement of bearing clearances in a diesel engine is a critical maintenance task essential for ensuring engine reliability, efficiency, and longevity. The clearance is the precise gap between the stationary bearing shell and the rotating journal, which is designed to be filled with a film of lubricating oil.
Its importance is founded on the principles of hydrodynamic lubrication:
1. **Formation of Hydrodynamic Oil Film**: The primary function of the clearance is to allow the formation of a wedge-shaped, high-pressure oil film that supports the journal and prevents metal-to-metal contact. The rotation of the journal draws oil into this wedge, generating a hydrodynamic lift. The clearance must be within strict manufacturer-specified tolerances for this film to form and function correctly.