Exam Question
(a) Explain why a purifier is not attaining its rated speed on starting from rest? (8)
(b) How do you select the appropriate Gravity disc of a Purifier? Why is this selection an important element in the purifier operation? (8)
Class 4 (4th Engineer)
MEP
📅 Apr 2025
Reference Answer
### (a) Reasons for a Purifier Not Attaining Rated Speed
A centrifugal purifier failing to reach its rated operational speed is a critical issue indicating excessive resistive torque that the drive motor cannot overcome. The causes can be systematically diagnosed by examining the electrical system, the power transmission mechanism, and the bowl assembly.
**1. Electrical System Faults:**
* **Low Voltage/Frequency:** An unstable or low power supply from the ship's grid will reduce the torque output of the electric motor, preventing it from accelerating the heavy bowl assembly to full speed.
A centrifugal purifier failing to reach its rated operational speed is a critical issue indicating excessive resistive torque that the drive motor cannot overcome. The causes can be systematically diagnosed by examining the electrical system, the power transmission mechanism, and the bowl assembly.
**1. Electrical System Faults:**
* **Low Voltage/Frequency:** An unstable or low power supply from the ship's grid will reduce the torque output of the electric motor, preventing it from accelerating the heavy bowl assembly to full speed.
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