Exam Question

### (a) Water Mixed in the Crankcase Oil (4 Marks)
**Causes:**
* **Leaking Cylinder Liner Sealing Rings:** This is a primary cause. Multi-stage air compressors often have water-cooled cylinder liners. These liners are sealed against the cooling water jacket using elastomeric O-rings. Over time, these O-rings can perish, harden, or become damaged due to thermal cycling, allowing cooling water to leak directly into the crankcase, emulsifying the lubricating oil.
* **Leaking Intercooler / Aftercooler Tubes:** Perforations or cracks in the cooler tubes allow high-pressure air to leak into the cooling water side, but can also allow cooling water to enter the air side, especially during shutdown periods when water pressure may exceed residual air pressure. This water is then carried with the air into the next stage, and can pass by the piston rings into the crankcase.