Page 10 - Know and Understand Centrifugal Pumps

Contents

7 Understanding Pump Curves 76
Pump performance curves 76
History 77
Head versus pressure 77
H-Q 78
Pump efficiency 80
The energy (BHp) curve 81
The pump’s minimum requirements (NPSH) 82
Special design pumps 85
Family curves 85

8 The System Curve 92
The system controls the pump 92
The elements of the Total Dynamic Head (TDH) 92
Determining the Hs 96
Determining the Hp 96
Calculating the Hf and Hv 97
The dynamic system 110
Variable elevations 110
The happy zone 113
Dynamic pressures 113
Variable resistances 116
Short term resistance changes 116
Long term resistance changes 117
Pumps in parallel and pumps in series 120
Pumps in parallel 122
Three tips 123
Pumps running in series 124
Combined parallel and series pump operation 125

9 Shaft Deflection 128
Introduction 128
Operation, design and maintenance 133
Signs of shaft deflection 136
Interpreting the evidence 137
The sweet zone 140
The dual volute pump 141

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