Page 9 - Know and Understand Centrifugal Pumps

Contents

Cavitation review 37
Do something about cavitation! 37

4 The Affinity Laws 39
Introduction 39
The Laws 39
The Affinity Laws and the impeller diameter 42
What’s the practical application of these laws? 42

5 Useful Work and Pump Efficiency 44
Useful work from a pump 44
Flow determination 46
Pump efficiency 48
Factors that affect the efficiency 48
Calculating pump efficiency 50

6 Pump Classification 51
Introduction 51
Positive displacement pumps 51
Centrifugal pumps 54
Conceptual difference 55
Centrifugal volute pumps 56
Types of centrifugal pumps 57
Overhung impeller 57
Impeller between the bearings 57
Turbine pumps 58
Specific duty pumps 58
The typical ANSI pump 58
API (American Petroleum Institute) pumps 59
Vertical turbine pumps 60
Non-metallic pumps 61
Magnetic drive pumps 62
Canned motor pumps 63
Pump impellers 64
Turbine impellers 65
Conventional impellers 66
Suction specific speed, Nss 66
Open impellers 70
Semi open impeller 71
Totally enclosed impeller 71
Wear bands 72
Specific speed, Ns 73