THE SEWAG E PUMPIN G HANDBOOK - Grundfos Danmark | Leverandør af

118 Pages·2002·8.79 MB·English

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THE SEWAGE
PUMPING
HANDBOOK

Foreword
Foreword
The use of submersible pumps in sewage and and construction is described in Section 2. Pump
drainage pumping applications has increased performance is dealt with in Section 3, offering
greatly in the last decades since they entered the methods for the calculation of pump performance
market. The introduction of heavy-duty submers- in various installations. Factors affecting pump
ible pumps with motor power ratings exceeding selection are also discussed. Section 4 offers infor-
500 kW has also made them available for central mation on pump testing. Basic design of pumping
municipal pumping duties. The good service stations is discussed in Section 5, offering design
record and high quality standard attained by information for both large and small applications.
these pumps has all but excluded the use of con- Continuous regulation of submersible pump oper-
ventional pumps in municipal service. ation by frequency control is described in Section
6. The concept of whole-life cost for pumps and
By the same token, the special characteristics of pumping installations is presented in Section 7.
submersible pumps have also required the devel- Matters relating to pump commissioning are pre-
opment of new knowledge on their implementa- sented in Section 8, whereas pump operation and
tion, such as the design of pumping stations. This servicing is described in Section 9. Section 10 deals
work has been advanced by both pump manu- with pumping station control and monitoring.
facturers and municipal engineers. Appendix A offers information on the hydraulic
characteristics of common pipe components for
The intention of this book is to bring the newest pipeline loss calculations. Appendix B presents a
information on both submersible pumps and method for the determination of sewage pump-
pumping stations to the use of all concerned ing station capacity and pump starting frequency.
professional people in a concise form. The book is
divided into Sections according to the related One objective of the book has been to make the
topics. contents easy to read and comprehend. The pre-
sentation is therefore enhanced with a large num-
Basic pump theory is described in Section 1, pro- ber of illustrations, providing examples of and
viding a reference background for the assessment complementary information on the matter at
of pump performance. Submersible pump design hand.
3

Table of Contents
Table of Contents 3.3.2 Local Losses ....................................................43
3.3.3 Rising Main Characteristic Curve .............43
3.4 Rising Main Size ............................................44
1 Pump Theory .............................................7 3.4.1 Economy .........................................................44
1.1 The Head Equation .........................................7 3.4.2 Free Passage for Solids ................................45
1.1.1 Flow with Losses or Addition of Energy ....7 3.4.3 Avoiding Settling of Solids and Sludge ...45
1.1.2 Fluid Flowing from a Container ..................8 3.4.4. Water Hammer..............................................45
1.2 The Basic Pump Equation .............................8 3.4.5 Avoiding Water Hammer ...........................47
1.3 Pump Curve and Losses ...............................10 3.5 Pump Duty Point ..........................................48
1.3.1 The Effect of Finite Number of Vanes ......10 3.5.1 Single Pump Operation ...............................48
1.3.2 Friction Losses Hf ..........................................10 3.5.2 Parallel Operation, Identical Pumps ........48
1.3.3 Discontinuity Losses Hs ...............................10 3.5.3 Parallel Operation, Different Pumps ........48
1.3.4 Leakage Losses Hv .........................................10 3.5.4 Serial Operation ...........................................49
1.3.5 Other Losses ....................................................11 3.5.5 True Duty Point ............................................49
1.4. Cavitation and NPSH .....................................11 3.6 Sludge Pumping ...........................................49
1.4.1 Definition of NPSH .......................................12 3.7 Complex Rising Mains ................................49
1.4.2 Reference Plane .............................................12 3.7.1 What Goes on in a Complex
1.4.3 Required NPSH ...............................................12 Rising Main? .................................................49
1.4.4 Available NPSH ..............................................14 3.7.2 Determination of Head ................................51
1.4.5 NPSH Safety Margin .....................................15 3.7.3 Pipe Size and Flow Velocity .........................51
1.4.6 Damming up of Suction Wells................... 15 3.7.4 Choice of Pump ..............................................51
3.7.5 Confirming Measurements ........................51
2 Pump Construction .................................16 3.8 Duty Point Evaluation for
2.1 General ............................................................16 Parallel Pumping Stations ..........................52
2.2 Pump ................................................................18
2.2.1 Impellers ..........................................................18 4 Testing of Pumps .....................................54
2.3 Motors .............................................................27 4.1 Testing Arrangements .................................54
2.3.1 General ...........................................................27 4.1.1 Production Testing .......................................54
2.3.2 Explosion-proof Motors ..............................27 4.1.2 Field Testing, Duty Point .............................56
2.3.3 Motor Cooling ...............................................27 4.2 Acceptance Tests ..........................................57
2.3.4 Motor Tightness ...........................................29 4.2.1 Testing Standards .........................................57
2.3.5 Motor Bearings ..............................................31
2.3.6 Motor Protection Devices ..........................32 5 Pumping Stations ....................................59
2.4. Pump Connection ........................................34 5.1 Pumping Station Basic Design ..................59
2.5 Construction Materials, 5.1.1 Wet Well Volume and Surface Area ........59
Corrosion and Wear .....................................36 5.1.2 Pumping Station Inlet Pipe .......................60
2.5.1 Corrosion Resistance ...................................36 5.1.3 Wet Well Floor Shape .................................60
2.5.2 Wear Resistance ...........................................37 5.1.4 Stop Levels ......................................................61
2.5.3 Abrasive Liquids ............................................37 5.1.5 Start Levels .....................................................62
5.1.6 Suction Pipe Dimension and Design .......62
3 Pump Performance ..................................38 5.1.7 Pumping Station Internal Pipework ........63
3.1 Pump Head ....................................................38 5.1.8 Flushing Devices ...........................................63
3.1.1 Submersible Pumps .....................................38 5.1.9 Odour Problems in Pumping Stations ....64
3.1.2 Dry-installed Pumps ....................................39 5.1.10 Pumping Station Design Examples .........64
3.2 Pump Performance Curves ........................39 5.1.11 Dry-installed Pump Positions ....................67
3.2.1 H Curve ...........................................................39 5.2 Package Pumping Stations ........................68
3.2.2 Efficiency Curves ..........................................40 5.2.1 Out-of-doors Pumping Stations ..............68
3.2.3 Power Curves .................................................40 5.2.2 Indoor Pumping Stations ...........................70
3.2.4 NPSH Curve ....................................................40 5.3 Pumping Stations with
3.3 Pipe Losses and Rising Main Column-installed Pumps ............................70
Characteristic Curves ...................................41 5.4 Pumping Station Dimension Selection ...72
3.3.1 Friction Losses ................................................41 5.4.1 Regular Sewage Pumping Stations ..........72
5
Table of Contents
5.4.2 Stormwater Pumping Stations ..................72 10.2.1 Wet Well Water Level Sensors ..................89
5.4.3 Combined Sewage Pumping Stations 10.2.2 Current Sensor .............................................90
and Retention Basins ...................................73 10.2.3 kWh Meter ....................................................90
5.5 Pump Selection ..............................................74 10.2.4 Phase Failure Relay ......................................90
5.5.1 Pump Selection Based on Pump Curves ..74 10.2.5 SARI 2 Monitoring Device ..........................90
5.5.2 Observing Pump Efficiency .........................74 10.2.6 ASM 3 Alarm Status Module ......................91
5.5.3 Number of Pumps .........................................75 10.3 Pump Control Units ......................................91
5.6 Special Considerations ................................76 10.3.1. Control Features ............................................91
5.6.1 Pump Vibrations ............................................76 10.3.2 Condition Monitoring Features ................92
5.6.2 Pump Noise ....................................................77 10.3.3 Parameters and Signals ..............................92
10.3.4 Data Logging and Analysis .........................93
6 Frequency-controlled Sewage Pumps ...........78 10.3.5 User Interface ................................................93
6.1 General ...........................................................78 10.4 Remote Control and Monitoring System 93
6.1.1 Pump Motor Selection ................................78 10.4.1 Different Levels for Remote Control ........93
6.1.2 Maximum Frequency ..................................78 10.4.2 Software and Hardware .............................94
6.1.3 Minimum Frequency and Minimum 10.4.3 Data Transmission .......................................95
Performance.................................................. 79 10.4.4 Alarm Transfer ...............................................95
6.1.4 Pump Frequency Curves .............................79 10.4.5 System Integration ......................................96
6.1.5 Pump Clogging .............................................80 10.5 Internet & WAP Based Remote Control
6.1.6 EMC Cable Requirement ............................80 and Monitoring .............................................96
6.1.7 Bearing Currents ..........................................80
6.1.8 High Tension ..................................................81 Symbols .............................................................98
6.1.9 Explosion-proof Motors ..............................81
6.1.10 Guaranteed Values .......................................81 APPENDIX A ......................................................100
6.1.11 Tests with Frequency Controller
(String Tests) ...................................................81 APPENDIX B.......................................................108
6.1.12 Collaboration with the Pump
Manufacturer .................................................81
7 Pump Whole-life Cost Evaluation ..........82
7.1 General ...........................................................82
7.2 Calculation Period ........................................82
7.3 Investment Costs .........................................82
7.4 Energy Costs ..................................................83
7.4.1 Efficiency Over Time ....................................83
7.4.2 Energy Usage Calculations ........................84
7.5 Maintenance Costs ......................................84
7.6 Cooperation With Pump Suppliers ..........85
7.7 Life Cycle Cost Publication .........................85
8 Commissioning .......................................86
9 Operation and Service ............................87
9.1 Safety ..............................................................87
10 Pumping Station Control and
Condition Monitoring .............................88
10.1 Local Control Methods ...............................88
10.1.1 Manual Control Units .................................88
10.1.2 Relay-based Control Units .........................88
10.1.3 Programmable Logic Controllers ..............88
10.2 Sensors for Pump Control and
Condition Monitoring .................................89
6
Pump Theory 1
1 Pump Theory are consequently called static head, pressure head
and kinetic head, respectively.

This section is a primer of fluid pumping theory The equation is essential for fluid mechanics and
and provides the reader with the theoretical back- can be used to account for many hydrodynamic
ground knowledge essential for deeper under- phenomena, such as the decrease in pressure that
standing of the pumping process. accompanies a reduction in a flow cross section
area. In this case the fluid velocity increases, and
1.1 The Head Equation for the total head to remain constant and assum-
ing the potential head remains unchanged, the
pressure term or static head, must decrease.
Figure 1 shows part of continuous fluid flow in a
duct. Between the two observation sections 1 and
2 no energy is transferred to or from the fluid and Fig. 1
the flow is assumed to be frictionless. Thus the
v
total energy of the fluid relative to a horizontal 1
reference plane T at the two sections must be p
1
equal. The total energy comprises components for
potential energy, pressure energy and kinetic 1
energy, and for a fluid particle with a mass m the Q
energy at the observation sections is as follows: v
2
h
p 1
2
Section 1 2
2
h
2
Potential mgh mgh
1 2
Energy T
Section showing flow of liquid through two obser-
Pressure p p
mg-----1- mg-----2- vation cross sections. T is a reference plane for the po-
Energy ρg ρg tential heads h1 and h2, p1 and p2 are the prevailing
pressures and v1 and v2 the fluid velocities at sections
Kinetic 1 2 1 2 1 and 2.
---mv ---mv
Energy 2 1 2 2
1.1.1 Flow with Losses or Addition of
where ρ is the fluid density and g the acceleration Energy
of gravity.
If there are losses in the flow between section 1
and section 2 in Figure 1, the head equation 1 can
For a flow without losses the total energy in sec-
be written
tion 1 and 2 will be equal, thus
2 2
p v p v
mgh +mg-p----1-+-1--mv2 = mgh +mg-p----2-+-1--mv2 . h1+ρ----g-1-+2----g1-- = h2+ρ----g-2-+2----g2--+Hr (2)
1 ρg 2 1 2 ρg 2 2
where H is the head loss.
r
Dividing both sides of the equation with the term
mg it is obtained
If energy is added to the flow by placing a pump
between section 1 and section 2 in Figure 1, the
2 2
h +-p----1-+-v---1-- = h +-p----2-+-v---2-- (1) equation 2 can be written
1 ρg 2g 2 ρg 2g
2 2
p v p v
h +-----1-+----1--+H = h +-----2-+----2--+H (3)
This equation is called Bernoulli's equation after 1 ρg 2g 2 ρg 2g r
the engineer who first derived it. The terms of the
equation are expressed as heads, and the terms
where H is the pump total head.
7
1 Pump Theory
1.1.2 Fluid Flowing from a Container To accommodate for losses present, a flow coeffi-
µ
cient is added to equation 6, whence
An example of the application of the Bernoulli
equation is the calculation of the flow rate of a
fluid flowing freely from an open container. q = µA 2gh
1 2 (7)
Figure 2 shows an open container with an outlet
µ
orifice near the bottom. For practical purposes the The flow coefficient is dependent on the shape
area A is assumed much larger than the orifice of the orifice, and can be obtained from text
1
books on the subject. If the fluid level in the con-
area A , and the atmospheric pressure p in the
2 1
tainer is allowed to recede, the level height h will
container is equal to that outside the orifice, p .
2 change, which will have to be accommodated for
in calculations.
Fig. 2
A p 1.2 The Basic Pump Equation
1 1
The basic pump equation is used to calculate and
design geometrical shapes and dimensions of
v centrifugal pumps. The basic pump equation is
1
h also used to deduce the pump Q/H curve.
A pump impeller vane and its associated velocity
v
2 vectors are shown in Figure 3.
T
v = absolute fluid velocity
A2 p2 = p2 w = velocity relative to the vane
u = perimeter velocity
Section of a fluid container with an outlet orifice near
v = tangential component of absolute velocity
u
the bottom. A and A are the cross section areas of the
1 2 v = radial component of absolute velocity
surface and the outlet orifice, h the height difference m
between surface and orifice centre line, v surface re-
1
cession velocity and v liquid outlet velocity through The relative velocity is parallel to the vane at any
2
the orifice. Ambient pressure is constant. given point.
Choosing the centre line of the orifice as the refe- Also vu1 = v1⋅cosα1 and vu2 = v2⋅cosα2
rence plane T, the term h is equal to zero and h
2 1
Assuming the flow to be without losses and the
equal to h. Because A is much larger than A , the
1 2 number of vanes infinite (∞), the familiar basic
2
kinetic head -v---1-- can be assumed as zero. Thus equation of pump theory can be derived using the
2g laws of mechanics. This relationship is known as
the head equation 1 can be written the Euler equation and is expressed as:
h = -v---22-- (4) Ht∞ = g-1--(u2vu2–u1vu1) . (8)
2g
where the index t refers to a flow without losses
whence and ∞ refers to the assumption of infinite number
of vanes ensuring complete fluid direction.
v = 2gh
2 (5)
In an actual pump neither of these assumptions
For volume flow without losses is obtained can be satisfied, as friction losses are always
present, and the finite number of vanes will not
direct the flow entirely in the direction of the
q = A 2gh
1 2 (6) vane.
8
Pump Theory 1
The reduction in head caused by losses in the flow It can be shown that both η and k are less than
h
η
is taken into account by the hydraulic efficiency h, unity. They will not be discussed in further detail
and the reduction due to the deviation of the flow here.
from ideal angle β is accounted for by a vane
2
coefficient k. With these modifications, the Euler Centrifugal pumps are normally designed with
equation for an actual pump reads as follows: α1 = 90 °, whence vu1 = 0.
η Thus the basic pump equation is simplified to
H = ----h--(ku v –u v )
g 2 u2 1 u1 (9)
u v
H = kηh----2--g----u---2-- (10)
Fig. 3
u
2
v
2
v
m
2
2
v
u
2
2
w
1
1
d
2
d
v 1
m
1
v
u
1
v 1
1
u
1
Pump impeller vane with the velocity triangles at leading and trailing edges. Fluid absolute velocity v, relative velocity
w, vane perimeter velocity u, liquid absolute velocity tangential component vu and radial component vm.
9