Q1: Which of the following options will facilitate the achievement of a very high head (say 30 metres) in case of a centrifugal pump?

ANS:C - Mounting of two or more impellers in series on a single shaft.

The option that will facilitate the achievement of a very high head (such as 30 meters) in the case of a centrifugal pump is: Mounting of two or more impellers in series on a single shaft.

Explanation:

1. Increasing Impeller Speed and Volute Area:
   • Increasing the impeller speed can increase the kinetic energy imparted to the fluid, but it may not significantly increase the static pressure (head) that the pump can achieve.
   • Increasing the volute area can affect efficiency and flow distribution but does not directly increase the head.
2. Increasing Number of Vanes in the Impeller:
   • Increasing the number of vanes in the impeller can improve efficiency and potentially increase the pressure rise per stage (impeller). However, there are practical limits to how much head increase can be achieved solely by increasing the number of vanes.
3. Mounting Two or More Impellers in Series:
   • Mounting multiple impellers in series on a single shaft allows each impeller to contribute to increasing the pressure (head) sequentially.
   • Each impeller adds its pressure rise to the total head, resulting in a cumulative effect. This configuration is effective in achieving higher heads than what a single impeller can achieve alone.
4. Conclusion:
   • While increasing impeller speed and volute area, as well as increasing the number of vanes, can contribute to pump performance, mounting two or more impellers in series is specifically designed to achieve very high heads efficiently.
   • Therefore, the correct option that facilitates achieving a very high head in a centrifugal pump is (c) Mounting of two or more impellers in series on a single shaft.