Exam Question
with reference to Centrifugal pumps, state the reasons for the following
(a) Pump fails to deliver water (6)
(b) Pump vibrates (5)
(c) Reduction in capacity (5)
Class 4 (4th Engineer)
MEKG
📅 Sep 2022
Reference Answer
### (a) Reasons for Pump Failing to Deliver Water (6 Points)
A centrifugal pump's failure to deliver water indicates a fundamental issue preventing it from generating differential pressure. The primary reasons are:
1. **Loss of Prime / Presence of Air in Casing**: A centrifugal pump is not self-priming. It must be filled with the liquid (primed) before starting. If air is trapped in the casing or suction line, the low-density air will just be churned by the impeller. The pump cannot generate the required low-pressure zone at the impeller eye to draw in the denser liquid, hence it fails to build head and deliver water.
* **Causes**: Leaks in the suction line piping, faulty foot valve, faulty gland packing on the suction side, or insufficient initial priming.
A centrifugal pump's failure to deliver water indicates a fundamental issue preventing it from generating differential pressure. The primary reasons are:
1. **Loss of Prime / Presence of Air in Casing**: A centrifugal pump is not self-priming. It must be filled with the liquid (primed) before starting. If air is trapped in the casing or suction line, the low-density air will just be churned by the impeller. The pump cannot generate the required low-pressure zone at the impeller eye to draw in the denser liquid, hence it fails to build head and deliver water.
* **Causes**: Leaks in the suction line piping, faulty foot valve, faulty gland packing on the suction side, or insufficient initial priming.
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