Exam Question

### (a) Conditions Requiring a Priming Device for a Centrifugal Pump
A centrifugal pump, by its design principle, is not self-priming. It operates by imparting kinetic energy to a liquid via a rotating impeller. This energy is then converted into pressure energy in the volute casing. This process is efficient for liquids, which are largely incompressible, but highly inefficient for gases like air, which are compressible and have a very low density. A priming device is therefore required to ensure the pump casing and suction line are completely filled with liquid before the pump is started.
The primary conditions under which a centrifugal pump requires priming are:
1. **Negative Suction Head (Suction Lift):**