Exam Question

### (a) Reasons for Purifier Overflow
A purifier overflow occurs when the oil being purified is discharged through the water outlet instead of the clean oil outlet. This indicates a failure in establishing or maintaining the correct oil-water interface within the bowl. The primary reasons are as follows:
1. **Insufficient or No Sealing Water**: The sealing water creates a liquid seal at the periphery of the bowl, preventing oil from escaping through the water outlet. If the sealing water supply is insufficient, fails, or is not introduced before the oil feed, a proper interface cannot be formed, leading to an immediate overflow.
2. **Excessive Back Pressure**: A regulating valve on the clean oil outlet maintains a specific back pressure. If this pressure is set too high, it resists the discharge of clean oil, forcing the oil-water interface to move inwards towards the bowl center. This can break the liquid seal and cause oil to be discharged with the water.