Volume 8 – Mechanical and Electrical Services - Malaysia Geoportal

Chapter 1 PUMPING INSTALLATION
Fig. 1.4 Variation in impeller profile with specific speeds and pump characteristic curves
Impellers of different types usually have widely different performance characteristics, as indicated by
the shapes of the characteristic curves for capacity, head, power and efficiency. Pumps of low
specific speed will have a relatively flat curve capacity while high specific speed pumps will exhibit a
steeper curve.
Flat curve pumps experience a large change in capacity with a moderate change in total head,
whereas a steeper head-capacity (H-Q) curve pumps have the advantage that a major change in
total head result in a small variation in capacity/flow rate.
March 2009 1-7