Characteristic curves of centrifugal pumps are defined those curves which are plotted from the results of a number of tests on the centrifugal pump. These curves are necessary to predict the behavior and performance of the pump when the pump is working unders different flow rate, head and speed. The following are the important characteristics curves for the pump:
i. Main characteristic curves
ii. Operating characteristic curves
iii. Constant efficiency or Muschel curves
Main characteristics curves of centrifugal pump
These are obtained by fixing the speed at some arbitrary value of and plotting serarately H,HP, & ηagainst Q. The rate of flow Q is caried by means of the quantity H, HP,ηare calculated. A number of different values of N are chosen and one such set of curves is drawn for each speed.
Fig 1.11 Main characteristics curves of centrifugal pump
Operating characteristics curves of centrifugal pump
Fig. 1.12 Operating characteristic curves of centrifugal pump
During operation the pump must run at a constant speed. Normally, this is the designed speed. The particular set of main characteristics which correspond to the designed speed is mostly used in operation and is therefore known as operating characteristics.
Muschal curve or Constant efficiency curve
With the help of data obtained from the above curve, a series of constt. Efficiency curve can be obtained. The facilitate the job of the salesman and enable the prospective customer to see directly the range of operation with a particular efficiency.
Fig. 1.13 Muschal curve or constant efficiency curve for centrifugal pump