Exam Question
(a) Describe why priming is required for centrifugal Pumps, With diagrammatic sketch describe working of priming arrangement for centrifugal pump. (10)
(b) Why balance holes are provided in the impeller? (6)
Class 4 (4th Engineer)
MEP
📅 Nov 2022
Reference Answer
### (a) Priming of Centrifugal Pumps
**(i) Necessity of Priming (Why Priming is Required)**
Priming is the process of filling the pump casing and the suction line with the liquid to be pumped, ensuring that all air is expelled before the pump is started. For a centrifugal pump, this is an absolute necessity due to its operating principle.
1. **Operating Principle:** A centrifugal pump operates by imparting kinetic energy to a fluid via a rotating impeller. This kinetic energy is then converted into pressure energy in the volute casing. The amount of pressure (or head) a pump can generate is directly proportional to the density of the fluid being pumped. The relationship is given by $$ P = \rho g H $$, where P is pressure, $$ \rho $$ is fluid density, g is acceleration due to gravity, and H is the head.
**(i) Necessity of Priming (Why Priming is Required)**
Priming is the process of filling the pump casing and the suction line with the liquid to be pumped, ensuring that all air is expelled before the pump is started. For a centrifugal pump, this is an absolute necessity due to its operating principle.
1. **Operating Principle:** A centrifugal pump operates by imparting kinetic energy to a fluid via a rotating impeller. This kinetic energy is then converted into pressure energy in the volute casing. The amount of pressure (or head) a pump can generate is directly proportional to the density of the fluid being pumped. The relationship is given by $$ P = \rho g H $$, where P is pressure, $$ \rho $$ is fluid density, g is acceleration due to gravity, and H is the head.
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