Planning information Amacan® submersible pumps in

KSB Know-how, Volume 6
Planning information
Amacan® submersible pumps in discharge tubes
Contents
Introduction
1.
The Amacan series
1.1
Impeller types and performance ranges
1.2
Calculation of operating points
1.3
Pump drive with frequency inverter
2.
Pump station design
2.1
General
2.2
Pump installation planning
2.2.1 Open intake chambers
2.2.2 Open intake chambers with suction umbrella
2.2.3 Covered intake chambers
2.2.4 Details of intake chamber design
2.2.5 Examples of pump station planning
2.2.6 Amacan K: A special case
2.3
Pump sump design
2.4
Solutions for special cases
2.5
The necessity of model testing
2.6
The significance of CFD simulation
2.7
Screening equipment
3.
Discharge tube design
3.1
Design variants
3.2
Details on discharge tube design
3.3
Cable connections
4.
List of references and photos
1
2
Introduction
In the fields of water and waste
More and more operators are
water technology, submersible
being won over by these advan-
pumps represent a viable eco-
tages – KSB’s Amacan pumps
nomic and technical alternative
work in irrigation and drainage
to conventional, dry-installed
pumping systems, waterworks,
pumps. In particular, they offer
sewage treatment plants, power
a number of handling advan-
stations, industrial water supply,
tages during maintenance and
water pollution and flood control.
installation work, a factor of
They handle raw and clean water
increasing importance in times
(groundwater, storm water, river
of general staff cutbacks by
water) as well as waste water and
operating companies.
activated sludge.
In the special case of submers-
With discharge tube pumps the
ible motor pumps in discharge
construction and design of the
tubes, there are significant
periphery – the pump station as
design advantages to be consid-
a whole – are crucial in ensuring
ered. For example, though they
economical and reliable oper-
have the same hydraulic capacity
ation, more so than is the case
as tubular casing pumps, sub-
with other pumps.
mersible motor pumps are a good
deal more compact in dimension
In addition to the selection of
(no long shaft assemblies, no
pump hydraulics, the structural
additional bearing locations in
requirements will also be exam-
the discharge tube). This means
ined in close detail in the follow-
additional buildings to accom-
ing pages, along with the plan-
modate the electric motor are
ning of the pump installation
not required, as the submersible
and the design of the pump sump.
pump and integral motor are
Finally, this brochure will con-
installed in the discharge tube.
sider relevant aspects of electrical
equipment.
The “Amacan ® Submersible
Pumps in Discharge Tubes”
brochure is primarily aimed at
pump station designers and
operators in the water and waste
water engineering sectors.
3
1
1.
The Amacan series
1.1
Impeller types and
performance ranges
of fluids – from grey water,
size for the pumping task in ques-
which is reasonably clean, right
tion. When making a selection, it
up to waste water or activated
is not only important to be aware
sludge. Selecting the right im-
of which impeller type is the right
Wherever higher flow rates have
peller type for a particular ap-
match for the pumped fluid, in
to be handled, submersible pumps
plication will depend upon the
some cases additional requirements
in discharge tube design have
nature of the pumped fluid and
in the design of the pump station
proved their worth in a wide
the pumping task. The following
and the choice of the technical
range of applications. These sub-
selection charts provide infor-
equipment must be observed for
mersible motor pumps can be
mation on the performance of
certain impeller types.
optionally fitted with three dif-
the different impeller types and
ferent impeller types enabling
help designers to choose the
them to deal with a wide variety
right Amacan pump type and
Channel impeller
Mixed flow impeller
Propeller
Amacan K
Amacan S
Amacan P
Fig. 1.1-a: Available impeller types for Amacan pumps
4
Fluids pumped
Notes and Recommendations
Waste water
- Check the free passage through the impeller
- Pre - cleaned via a sreen or weir
River water
- Pre - cleaned via sreen or shingle trap
Storm water /
waste water
- Check the free passage through the impeller
- Pre - cleaned via a sreen or weir
- With a propeller a special casing wear ring may be
necessary
Activated sludge
- Max. 1% dry solids content
Seawater
- Check possible material combinations or fit
anodes with six-monthly check- ups
1.1
Impeller types and performance ranges
H [m]
ft
20
A4 1200-870
10 pol
B4 600-350
4 pol
B4 700-470
6 pol
B4 1000-700
8 pol
B4 1200-870
10 pol
50
B4 1500-1060
12 pol
40
B4 800-540
6 pol
10
A4 800-540
6 pol
A4 600-350
4 pol
5
A4 500-270
4 pol
4
A4 1000-700
10 pol
A4 700-470
8 pol
G3 2100-1480
A4
1200-870
12 pol
10
A4 500-270
6 pol
2
30
A4
1500-1060
14 pol
20
A4 800-540
8 pol
A4 600-350
6 pol
3
A4 700-470
6 pol
A4
1500-1060
12 pol
A4
1000-700
8 pol
G3 2100-1480
5
4
1
200
300
400
100
500
1000
200
300
2 000
400 500
3 000 4 000 5 000
1000
10 000
2 000
20 000
3 000 4 000 5 000
30 000 40 000 50 000 Q [m 3 /h]
10 000
Q [l/s]
Fig. 1.1-b: Selection chart Amacan P pumps (50 Hz)
Fig. 1.1-c: Amacan P
5
1.1
Impeller types and performance ranges
H [m]
60
Engineered
Engineered
programme
50
40
-620
n=960 min -1
30
20
10
-405
n=1450 min -1
-404
n=1450 min -1
-364
n=1450 min -1
-505
n=960 min -1
-365
n=1450
min -1
-600
n=960 min -1
-550
n=960 min -1
-550
n=725
min -1
-535
n=960 min -1
-615
n=960
min -1
-820
n=580 min -1
5
4
- 655
n = 725 min - 1
3
2
1.5
200
700
300
400
1000
500
2000
1000 1200
3000
1600 2000
4000 5000
Fig. 1.1-d: Selection chart Amacan S (50 Hz)
Fig. 1.1-e: Amacan S
6
3000
10000
4000 5000
20000
8000
Q [l/s]
30000
Q [m 3 /h]
1.1
Impeller types and performance ranges
H [m]
ft
40
100
30
20
K1000 - 500 6p
50
40
K800 - 370 6p
10
K700 - 330 4p
K1000 - 420 6p
K1200-630 6p
30
K700 - 371 6p
K800 - 400 6p
K700 - 330 6p
K700 - 324 6p
5
4
20
K1000 - 421 6p
K1200 - 630 8p
K700 - 371 8p
3
10
K700 - 324 8p
K1200-630 10p
2
K800 - 400 8p
5
4
1
100
30
200
40
50
300
400
100
500
1000
200
300
2000
400
500
3000
4000 5000 6000
1000
Q [m 3 /h]
Q [l/s]
Fig. 1.1-f: Selection chart Amacan K (50 Hz)
Fig. 1.1-g: Amacan K
7
1.1
Impeller types and performance ranges
The design configuration of
installation. In addition, build-
on the on-site installation depth.
modern submersible motor
ings to accommodate electric
This lifting equipment represents
pumps installed in discharge
motors or ventilation equipment
a major investment even though
tubes has a number of advan-
are not required. The drive is
it is only periodically used for re-
tages over that of conventional
an integral part of the submers-
pair work or pump installation /
tubular casing pumps. For ex-
ible pump and hence is contained
removal. In contrast, to carry
ample, although these pumps
in the discharge tube.
out the same tasks the Amacan
submersible motor pumps only
have the same hydraulic capacity (impeller) they are consid-
For assembly and maintenance
require mobile cranes, which are
erably more compactly dimen-
work on conventional pumps it
far more cost effective. In order
sioned (no long shaft assem-
is generally common practice to
to fully exploit this advantage,
blies, no additional bearing
install large lifting equipment,
appropriate access must be fac-
locations in the discharge tube).
the size of which will depend
tored in at the planning stage.
The handling of a submersible
pump is significantly more
straightforward, simplifying in
particular maintenance and
Fig. 1.1-i: Installation of submersible motor pump with a mobile crane
Fig. 1.1-h: Conventional tubular casing pump
8
Fig. 1.1-j: Pump station with building
1.2
Calculation of operating points
1.2
Calculation of operating points
As propeller pumps in particular
in low-lift pump stations.
often generate only a low head,
During pump selection, these
the loss of head at the pipe out-
maximum water levels should
let (a check valve is often in-
not lead to unacceptably low or
With Amacan pumps, the
stalled!) must be considered in
high discharge heads, as this
manometric head required for
the calculation. When establish-
would mean the pump is oper-
a certain flow rate will be cal-
ing the static head component,
ating to the left of Qmin or to
culated using the same approach
the maximum differences be-
the right of Qmax .
as with any centrifugal pump.
tween the suction and discharge
side liquid levels of the pump
The documented pump charac-
station are of interest, especially
teristic curves already include
the internal losses between the
impeller inlet and 0.5 m behind
tube losses before and after
these points and head losses
through flow deflection, fittings
(valves etc.) and the outlet are
Head H total
the motor. Inlet and discharge
System curve HA
Dynamic component = H dyn
to be taken into account as the
Static component = H stat
dynamic head component.
The system curve is composed
Q req
Flow rate Q
of the static head component
(difference in water levels) and
Fig. 1.2-a: Example of a system curve [H = f(Q)]
the dynamic head component
(friction loss in the pipes and
m 11
10
fittings):
ft
Q min
8
20
6
H tot = H stat+ H dyn
H stat max
H stat min
4
17˚
2
0
v2
v2
L
H dyn = ∑ λi x i x i + ∑ ξi x i
2g
2g
di
i=n
i=n
i =1
i =1
0
0
1000
2000
3000
4000
5000
6000
m 3 /h
Fig. 1.2-b: Ilustration of possible water levels
i indicates the considered section of the pipe with the pipe length Li , the pipe diameter d i and the friction loss coefficient ξ i as well as the flow
velocity v i in the pipe section.
9
1.2
Calculation of operating points
If some loss coefficients ξ i are
In addition to the fluid level
unknown when calculating the
above the impeller (dependent
dynamic head component, then
on size) and the water level
the literature given at the end of
limit to prevent air-entraining
the brochure may be of assist-
vortices (dependent on flow
ance (e. g. Selecting Centri-
rate) – both are illustrated in
fugal Pumps [1]).
Fig. 1.2-c – the NSPH value of
the pump at the operating point
When selecting pumps installed
is of importance for the required
in discharge tubes particular
water level t1. The condition to
attention must be paid to the
be fulfilled is as follows:
difference in water levels, as the
minimum water level Wlmin in
NPSHavailable > NPSH required+ 1.0 m safety allowance
the structure must not be lowered
below the water level t1 required
If this condition is not fulfilled,
for the volume flow rate of the
the value for t1 must be increased
pump; this is the only way to
by the value of the difference
avoid surface vortices. The necessary depth tps of the pump
tps = wl min – t1
station building can also be calculated using this water level.
The minimum water level is a
function of the volume flow rate
wl min
1
2
3
4
5
6
7
required of the pump [t1 = f(Q)]
and also of the intake chamber
design (see sections 2.2.1 to
Amacan P ... 500- 270
Amacan P ... 600- 350
Amacan P ... 700- 470
Amacan P ... 800- 540
Amacan P ... 1000- 700
Amacan P ... 1200- 870
Amacan P ... 1500-1060
t1
t ps
Note:
Compare t 1 tables in the type series
booklets for the appropriate pump
size, installation variant and volume
flow rate.
2.2.3).
t 1 [mm]
4000
7
6
3000
5
2500
4
2000
3
2
1600
1
1200
1000
800
600
500
400
0.1
0.2
0.3
0.4
0.6
0.8
1
1.5
2
2.5 3
4
5
6
8
Q [m 3 /s]
Fig. 1.2-c: Calculation of the minimum water level t1
for Amacan P (for Amacan K and Amacan S refer to
the appropriate type series booklet)
10
1.2
Calculation of operating points
h V Kr [m] 1.0
20 0
0.8
0.6
25 0
0.5
110
0
120
0
130
0
14 0
150 0
16 0 0
0
900
10 0
0
800
70 0
600
50 0
400
2
0.2
DN
–.–.–.–
=3
50
30 0
0.3
DN 2
–.–.–.–.–.–.–.–.–
0.4
0.10
0.08
0.06
0.04
0.02
0.1
0.2
0.3
0.4 0.5 0.6
0.8
1
2
3
4
5
6
Q [m 3 /s]
Fig. 1.2-d: Determining the pressure loss
in a discharge elbow outlet
Should the discharge tube be
If there is no other data available,
open at the top (free overflow
then the overflow head h overfl
from the tube, for instance)
can be taken from the following
then the overflow head h overfl
diagram.
must be taken into account
when calculating the total pump
head H tot.
h ü [m] 2
D out
h overfl
7°
1
Q
D
The overflow head h overfl depends on Q and the
outlet diameter D out . The chart values are only
applicable if the fluid overflow is undisturbed to
all sides, (i.e. there are no obstructions) otherwise they can only be considered as approximate
values.
0.8
0.6
0.5
0.4
0.3
DA
=4
0.2
00
mm
60
0
0
00
10 0 0
12 0 0
00
14 0 0 18 0 0 00
2 20
16
2
80
0.1
0.1
0.2
0.3
0.4
0.5 0.6
0.8
1
2
3
4
5
6
Q [m 3 /s]
Fig. 1.2-e: Establishing the overfl ow head hoverfl
11
1.2
Calculation of operating points
After the system curve has been
determined, this should always
be plotted together with the
pump characteristic curve in
order to check the operating
points (curve intersections).
In this way, the designer can
ensure that no operating conditions outside the permissible
section of the characteristic
curve arise.
Fig. 1.2-f: Selection principle for Amacan pumps
according to the type series booklet
12
1.3
Pump drive with frequency inverter
1.3
Pump drive with
frequency inverter
(a) the flow velocity in the dis-
operate at the same speed. This
charge tube must be adequate
is to avoid the pumps blocking
to assure the pumping of fibres
each other in the low-flow
and solids that might have to be
operating range (with the nega-
Basically all pump motors can
handled (vmean > 2 m/s), and
tive effects on impeller, shaft
be used with frequency invert-
(b) the circumferential speed on
seal and bearings this can have).
ers. The characteristic curves of
the impeller’s outside diameter
Amacan pumps installed in
(not less than 15 m/s). When
If checking the minimum flow
discharge tubes can be calculated
speed is changed, and taking
velocity poses problems, under
using the affinity laws, as is
into account variable water
some circumstances (depending
also the case with centrifugal
levels, it is vital that no operat-
on the fluid pumped) it is
pumps.
ing point lies to the left of the
possible to work with slightly
permissible operating limit.
reduced values. To ensure the
This means: The limit speeds
pumps are not clogged, an
must be matched to comply
automatic control can increase
with the actual water levels.
the speed for a short period and
Q2 n2
=
Q1 n1
()
n
H2
= 2
n1
H1
2
()
n
P2
= 2
n1
P1
3
n1 Original speed
n 2 New or proposed speed
at set time intervals to activate
If two or more pumps with a
flushing. After this procedure
In principle, the aim of speed
common discharge pipe are run
the pumps’ speed can be
control is to optimally match
via frequency inverters, it is re-
lowered, automatically again, to
the pump’s operating point to
commended that all pumps
the original level.
the actual system requirements.
As mentioned above, three
impeller types with different
characteristics are available for
this submersible motor pump
ft
m
11
Q min
10
8
type in discharge tube design.
20
6
For each of these impeller types
4
it is always important to check
the control range. This includes
establishing the system curve(s)
with H stat,min and H stat,max.
2
n = 591
0
0
1000
2000
3000
4000
n = 690
n = 788
n = 985
0
5000
6000
m /h
3
The following must also be
checked:
n = 887
Fig 1.3-a: Amacan P 800 - 540 A 4 with speed curves
13
2.1
Pump station design
2.
Pump station design
2.1
General
pump(s) as well as the specifi-
According to Prosser [6], the
cation for the minimum spacing
criteria for unsatisfactory pump
between the pumps or, in some
station design can be clearly
The structural requirements of
cases, the dimensions to be ob-
defined and assessed. Poorly
a pump station are largely deter-
served for any necessary intake
performing pump sumps can
mined by how it is to be used.
chambers.
arise from the following:
mechanical requirements, con-
If the requirements regarding
1. Undersized control gates
sideration must also be given to
intake chamber dimensions,
hydraulic (fluid dynamics)
minimum water levels or the
aspects in the planning and
geometry of hydraulic areas
execution of the construction
within the pump station are not
work. The first part of the
met, i. e. deviations occur dur-
flow areas (e.g. diffusers
hydraulic areas to be designed
ing the planning or construction
with too large an angle of
is the inlet upstream of the
phase, proper functioning of
divergence)
pump station, followed by the
the entire station can no longer
4. Steep slope
intake chamber upstream of the
be guaranteed. In such a case, it
5. Weirs with no provision for
pump(s), parts of which may
is irrelevant whether these prob-
dissipating the energy of the
require a special shape, and
lems are caused by single or
falling fluid
finally the discharge pipe or
multiple deviations.
discharge system.
The conditions for pump oper-
Alongside purely structural and
ation are not met due to these
and valves
2. Abrupt changes in flow direction (e.g. sharp corners)
3. Submerged high velocity
6. Blunt pillars, piers and guide
vanes
7. Any design, or mode of op-
The pump manufacturer’s aim
modifications or deviations and
eration, which leads to
is to specify in the product’s
the problems arising as a result
asymmetric distribution of
technical documentation the
are reflected in either the cen-
the flow into the sump
dimensions (e.g. geometry of
trifugal pump’s operating be-
8. Inlet to the sump above the
the building) required for the
haviour or its performance. If
installation of the centrifugal
the pump manufacturer’s speci-
pumps. The reference values
fications on the hydraulic and
Items 1, 2, 3, 6 and 7 may cause
provided here are essential for
mechanical design aspects of
swirls at the pump’s inlet. Air-
the planning process, in par-
the pump station are taken into
entraining surface and sub-
ticular for establishing the main
account in the overall layout
merged vortices may form in
dimensions of the pump station.
early enough, malfunctions
extreme cases.
The successful planning of a
such as not achieving the re-
Items 4, 5 and 8 can produce
pump station is a complex task
quired performance data and
aeration while items 3, 4 and 5
which encompasses questions
operating troubles can be elim-
may cause unsteady flow
on how to design the area
inated.
conditions within the sump.
between the intake and the
14
water level.
2.1
Pump station design
The purpose of a pump sump is
to provide liquid storage and
good flow conditions to the
pump; therefore, it is important
to avoid the following undesirable hydraulic conditions:
1. Jets, or high-velocity flows,
discharging into stagnant
or slowly moving fluids (as
these form large, unsteady
eddies as downstream wakes)
2. Areas of separated flow
3. High-velocity flows
Fig. 2.1-a: Vortices developing as a result of
unacceptable approach flows into the chamber
– jet directly impinging on discharge tube
(v > 2 m/s)
4. Unsteady flow
5. Large surface waves
6. Free-falling fluids.
Observing the above criteria at
the planning and construction
phase is an important step towards creating a smoothly
functioning pump station.
KSB’s intake chamber geometries compare favourably with
those specified by other pump
manufacturers and internationally recognised research institutions in their literature. The
intake chamber geometries
suggested by KSB in their type
series booklets and software
tools allow smaller pump
stations to be built and therefore lower building costs.
15
2.2
Pump installation planning
2.2
Pump installation
planning
After all hydraulic aspects regarding the distribution of the
volume flow have been consid-
Fig. 2.2-a: Variants of discharge tube design
with free discharge
ered and the appropriate pump
size chosen, the geometry of the
intake chamber must be determined.
Thanks to a flexible discharge
tube design, Amacan pumps
offer a vast range of installation
options, making optimum pump
station design possible. This
gives system designers the flexibility to adapt the installation
Fig. 2.2-b: Variants of discharge tube design
with above-floor discharge nozzle
to any station design and system
condition. Some installation
options are briefly presented here.
Fig. 2.2-c: Variants of discharge tube design
with underfloor discharge nozzle
16
Fig. 2.2-d: Discharge tube design variant with underfloor
discharge nozzle, top floor suitable for vehicles
2.2
Pump installation planning
The primary source of advice
When determining the appro-
Whether the pump station is
on planning should be the pump
priate intake chamber geom-
equipped with one or several
manfacturers’ documentation
etry, the pump station designer
pumps has no influence on the
and internationally recognised
must also consider any operat-
intake chamber dimensions or
standards (cf. References).
ing conditions which will occur
the discharge tube.
when the pump station is being
Once the pump station’s dimen-
operated with a reduced num-
sions have been roughly defined,
ber of pumps. This may result
detailed planning of the installa-
in substantially different intake
tion of the pump should be
chamber flow conditions in
carried out in close consultation
terms of inflow velocity and in-
with the manufacturers’ tech-
flow direction (see section 2.3).
nical literature (e.g. type series
booklet or selection software),
where detailed information on
the exact dimensions required
v
b
for each particular pump size
can be found. It is vital that
e1 Distance between pump
and rear wall
l
these dimensions be observed to
ensure problem-free pump
b
Approach channel width
l
Length of approach channel
with uniform, straightened
flow, where changes in flow
direction do not occur
v
Mean flow velocity in
approach channel
operation.
Information on permissible
maximum inflow velocities and
the direction of inflow for the
Q Volume flow rate
t1
t3
specific intake chamber geometries is also provided (see
section 2.3).
The dimensions essential for the
intake chamber are its width
and length as well as the distances between rear wall / floor
and pump. The minimum water
level has to be established on
the basis of the pump’s volume
flow in order to ensure smooth
pump operation without air-
t1 Minimum submergence
t 3 Distance between floor
and pump
e1
Fig. 2.2-e: Important intake chamber data (for actual
dimensions refer to the type series booklet or selection
e1 Wandabstand zw. Pumpe und hinterer Schachtwand
software)
B Breite des Zulaufkanals
L Länge des Zulaufkanals mit gleichförmiger gerichteter
Strömung, wo keine Richtungswechsel stattfinden
V mittlere Strömungsgeschwindigkeit im Zulaufkanal
Q Volumenstrom
t1 Mindestüberdeckung
t3 Bodenabstand
entraining surface vortices.
17
2.2
Pump installation planning
2.2.1
Open intake chambers
If the water level in the pump
sump is sufficiently high and
the flow approaches the chamber directly from the front,
Vent pipe
with a tolerance of 10 degrees
maximum, then this form of
intake chamber design is the
most cost-efficient variant.
The flow velocity must not
Minimum
water level
exceed 1 m/s within the intake
chamber. Flow approaching the
10 degrees must be ruled out to
t1
pump at an angle of more than
t3
avoid flow separation and
vortex formation. This also
applies in the event of altered
operating conditions.
d8
b1
Flowstraightening
vane
b
Inflow
b1
e1
0 -10˚
Vmax = 1 m/s
l
Fig. 2.2.1-a: Open intake chamber without suction umbrella
(see the type series booklet for the actual dimensions)
18
2.2
Pump installation planning
2.2.2
Open intake chambers
with suction umbrella
If a check of the minimum
water level in the pump sump
establishes that this is insuffi-
Vent pipe
cient, another chamber variant
that provides sufficient submergence to prevent airentraining vortice should be
chosen. One such option, involving a few changes, is the
Minimum
water level
open intake chamber with a
suction umbrella. This allows
suction side minimum water
t1
the pump to operate at a lower
t3
level t1 with the same pump size
and the same operating point.
d8
d9
e1
Flowstraightening
vane
b
Inflow
0-10˚
Vmax = 1 m/s
l
Bild 2.2.2-a: Open intake chamber with suction umbrella
(see the type series booklet for the actual dimensions)
19
2.2
Pump installation planning
2.2.3
Covered intake
chamber
A special type of chamber is the
covered intake chamber. It allows
the lowest minimum water levels
Vent pipe
without the occurrence of airentraining surface vortices and
can accommodate flows
approaching at an angle of
0 to 90 degrees at 1 m/s max.
However, this variant involves
higher construction costs than
Minimum
water level
the chamber types previously
described. This type of chamber
under unfavourable approach
45˚
t3
has more than proved its worth
flow conditions and low water
levels.
d
e2
b2
b
Inflow
b1
Flowstraightening
vane
0-90˚
Vmax = 1 m/s
l
e1
Fig. 2.2.3-a: Covered intake chamber
(see type series booklet or selection software for the actual dimensions)
20
2.2
Pump installation planning
2.2.4
Details of intake
chamber design
Mounting a flow-straightening
vane under the pump inlet is
important in all intake chamber
designs for Amacan P and
Unlike pumps from the Amacan
Amacan S pumps as this device
K series, Amacan P and Amacan
prevents the occurrence of a
S pumps have to be installed in
submerged vortex which may
dedicated compartments in the
cause a drop in performance,
intake chamber. An important
among other things. This vane
criterion for the chamber walls
can either be a concrete or steel
is a minimum height of 150 mm
construction.
above the maximum water level
The precise vane dimensions
in the pump sump. This is to
are stipulated in the type series
ensure that the shape of the
booklet or selection software.
chamber does not favour vortex
formation even under maximum
water level conditions.
approx. 150 mm
Cast flow-straightening vane
Steel profile
b2
H max
b1
b1
H min
hR
hR
Screwed to intake
chamber floor
Fig. 2.2.4 -a: Chamber wall height
The walls in the intake section
of the chamber should always
Flow-straightening
vane concentric to
the pump centreline
be rounded to rule out the pos-
Discharge tube
sibility of additional vortices
forming if the flow to the chamber is skewed. This requirement
is vital for both single-pump
intake chambers with approach
flows from the side and multiple-
IR
IR ≈ 2 x D
h R = 0,4...0,6 x t 3
IR
Fig. 2.2.4 -c: Sizing the flow-straightening vane
pump chambers with central
inlet flows.
W
1
R≈ – W
2
Fig. 2.2.4 -b: Chamber intake design
21
2.2
Pump installation planning
Experience gained over the past
For this purpose, mounting
The intake chamber surfaces as
few years has shown that the
devices for stop logs can be
well as the wall around the
costs for concrete formwork in
integrated into the chamber wall
pump sump should have rough
the chambers can be reduced by
or the chamber can be shut off
concrete surfaces. If the areas in
using straight contours. Concrete
by appropriate flood gates. If
contact with the pumped fluid
fillings are, however, needed in
these mounting devices
are too smooth or even provided
areas where dead water zones
constrict the free flow cross
with a paint coat, this may lead
could occur. The intake chamber
section, the distance be-tween
to the reduction of the wall
corners must then be filled with
the pump and this point of flow
shearing stress – and thus in-
concrete up to a minimum height
disturbance must be checked
crease the risk of vortex forma-
of 150 mm above the maximum
and increased where necessary.
tion (submerged vortices, and
water level.
possibly surface vortices). The
Depending on the pump station
roughness of surfaces in contact
concept, the designers may allow
with the fluid should range from
for the possibility of shutting off
1 to 3 mm.
and draining individual intake
chambers, if required.
b2
D
e1
AK
AR
b1
v
LS
b
Flow
Straightening
vane
Ls = D x f
1.0
l
AR
AK
f
0.5
Flow straighteners
are required (consult KSB)
Fig. 2.2.4 -e: Corner fillets
0
5
f [%]
10
Fig. 2.2.4 -f: Influence of cross-sectional constriction
22
2.2
Pump installation planning
In some circumstances, it might
These special options must be
be necessary to adapt the intake
sized to precisely match the
structure to the specific require-
project data, which should,
ments of a project. It is conceiv-
therefore, only be done after
able, for instance, that an intake
consultation with the respon-
elbow might be employed in
sible KSB Competence Center.
place of a chamber. These elbows
have properties comparable
If special solutions are unavoid-
with those of covered intake
able for certain projects, these
chambers, i.e. they straighten
should be examined with ap-
the flow and ensure an even
propriate model tests and/or
distribution of flow velocity
CFD (Computational Fluid
across the inlet cross section of
Dynamics) simulations. As this
the pump.
means they are not standard
Fig. 2.2.4 -i: Variant of a double
elbow in a model test
solutions (see sections 2.5 and
2.6) it is important to obtain
prior assurance of the troublefree functioning of the system
under these specific project
conditions.
l2
l2
LW
r3
α2
r2
c2
d2
c1
α1
c1
a1
a1
L
5
d2
d1
r1
α1
d1
l3
1
b2
b1
2
b3
b4
b5
l4
α1
4
3
b6
b7
b8
b8
b 10
Fig. 2.2.4 -h: Variant of a segmental bend
23
2.2
Pump installation planning
2.2.5
Examples of pump
station planning
Variant 1
Variant 2
Given:
Solution:
Given:
Using three pumps, the pump
Each pump is to be provided
The pump station consisting of
station is to pump fluid from a
with an intake chamber sized to
three pumps is to convey fluid
channel. The inflow to the
match the respective pump (see
from a pump sump which is fed
pumps is described as being
the type series booklet or selec-
with fluid from an off-centre,
even across the channel width.
tion software). This ensures
front pipe / channel. In addition,
defined approach flow condi-
the pumps are installed asym-
tions and rules out any possi-
metrically with regard to the
bility of the pumps influencing
inflow; intake chambers have
each other during pumping.
not been provided.
v̄
v̄
Problem:
As the distance between the
discharge tubes and the rear
wall is too big, vortices may
develop behind the discharge
tubes as a result of separated
Problem:
flow. The absence of intake
The off-centre inflow into the
chambers creates the risk of the
pump sump causes an anti-
pumps influencing each other
clockwise rotation of the fluid
and of undefined approach flow
in the pump sump. The velocity
conditions in the case of single
in the inflow channel / pipe
pump operation.
determines the intensity of this
rotation and, as a consequence,
e1
L min
that of the uneven approach
flow.
b
v̄k <
– 1 m/s
e1
l min
v̄
b
min 5 x D
>1.3xDi
v̄k <
– 1 m/s
24
Di
2.2
Pump installation planning
Variant 3
Solution:
Given:
Solution:
Each pump is to be provided
The pump station consisting of
A curtain wall with an opening
with a complete intake chamber
three pumps is to operate from
towards the floor is installed
sized to match the respective
a pump sump which is fed with
upstream of the intake chambers.
pump (see the type series
water from an off-centre, front
This prevents rotation and
booklet or selection software).
pipe/channel. In addition, the
ensures the intake chambers are
This will rule out any possibil-
pumps are installed asymmet-
approached from the front
ity of the pumps influencing
rically with regard to the in-
without pre-swirl occurring.
each other during pumping.
flow; intake chambers have not
A curtain wall with an opening
been provided.
towards the floor is to be installed to ensure a uniform
v̄
approach flow. This will help
prevent the fluid from rotating.
Problem:
The off-centre inflow into the
pump sump causes an anticlockwise rotation of the fluid
in the pump sump. The velocity
in the inflow channel / pipe
determines the intensity of this
rotation and, as a consequence,
that of the uneven approach
flow.
e1
l min
v̄
b
Di
min 5 x D
>1.3xDi
v̄k <
– 1 m/s
25
2.2
Pump installation planning
Variant 4.2
Variant 4.1
Given:
Solution:
Given:
Using three pumps, the pump
Each pump is provided with a
Three pumps are installed to
station is to pump fluid from a
complete intake chamber sized
pump fluid from one pump
channel. The flow from the
to match the respective pump
sump. The flow approaches the
channel approaches the pumps
(see type series booklet or selec-
sump in the centre. The pumps
laterally. The pumps are separ-
tion software). The intake
are installed perpendicular to
ated from each other through
chambers should be installed on
the flow direction and do not
free standing baffles.
the sump wall opposite the
have intake chambers.
inflow. A curtain wall should
To reduce the velocity in the
be installed across the entire
sump the inlet channel has been
width of the pump sump up-
widened. Relative to the inflow,
stream of the intake chambers.
the distance between the pumps
This prevents the pumps from
and the rear wall is extremely
influencing each other during
large.
v̄
the pumping process; the approach flow is even.
Problem:
The flow moving from the
e1
l min
α > 15˚
v̄
b
channel into the sump is symmetrical with respect to the
min 5 x D
installation set-up of the pumps.
v̄k <
– 1 m/s
Vortices may, however, form as
v̄
Di
>1.3xDi
a result of flow separation; this
Problem:
leads to the risk of uneven
Due to the fluid approach from
velocity distribution among the
the channel to the sump, vortices
pumps. The absence of any in-
caused by flow separation are
take chambers means an un-
likely, leading ultimately to the
defined approach flow, with the
risk of uneven velocity distribu-
accompanying risk of the pumps
tion upstream of the pumps.
influencing each other.
The angle of divergence is too
wide and causes problems with
vortices and velocity distribution as mentioned above. As intake chambers are not available,
there is the risk of the pumps
influencing each other and of
undefined flow.
26
2.2
Pump installation planning
Variant 5
Solution:
Given:
Solution:
Each pump is provided with a
The pump station consisting of
Each pump is provided with a
complete intake chamber sized
three pumps is to pump fluid
covered intake chamber. As a
to match the respective pump
from a channel. The pumps do
result, perpendicular flows of
(see type series booklet or selec-
not have intake chambers and
up to a maximum of 1 m/s can
tion software). The intake
the fluid flow approaches the
be handled without any
chambers are installed on the
line of pumps perpendicularly.
problems. The intake chambers
are sized to match the actual
sump wall opposite the inflow.
pump size (see type series
A curtain wall should be inv̄
stalled across the entire width
booklet or selection software).
of the pump sump upstream of
The front edges of the intake
the intake chambers. This
chambers should be in line with
prevents the pumps from influ-
the channel wall to avoid
encing each other during
additional flow constrictions
pumping; the flow is even.
e1
Problem:
and marked differences in flow
The pump station consisting of
velocities in the channel.
three pumps is to pump fluid
l min
from a channel. The pumps do
b
not have intake chambers and
α > 15˚
v̄
min 5 x D
Di
the fluid flow approaches the
line of pumps perpendicularly.
v̄k <
– 1 m/s
>1.3xDi
v̄ <
– 1 m/s
27
2.2
Pump installation planning
Variant 6
Variant 7
Given:
Given:
Solution:
The pump station consisting of
The pump station consisting of
Each pump is provided with a
three pumps is to pump fluid
three pumps is to pump fluid
complete intake chamber sized
from a channel. The pumps are
from a channel. The flow is
to match the respective pump
installed in a series. The pumps
described as being even across
(see type series booklet / selec-
are not separated from each other
the entire channel width. The
tion software). This will rule
through chambers or baffles.
pumps are separated from each
out any possibility of the pumps
other through profiled rear
influencing each other.
walls of the sump.
Problem:
The approach flow from the
channel creates the risk of vortices caused by flow separation
and uneven velocity distribution
up- and downstream of the
pumps. The absence of any intake chambers means an undefined approach flow, with the
Problem:
accompanying risk of the pumps
The absence of any intake
influencing each other.
chambers means an undefined
approach flow, with the accomv̄ <
– 1 m/s
panying risk of the pumps influencing each other. This
results in unpredictable flow
conditions particularly during
operation with a reduced
number of pumps.
Solution:
Each pump is to be provided
e1
l min
with a covered intake chamber
sized to match the respective
pump (see type series booklet
or selection software). This will
rule out any possibility of the
pumps influencing each other,
while the flow conditions are
exactly defined.
28
b
v̄k <
– 1 m/s
2.2
Pump installation planning
2.2.6
Amacan K:
A special case
building structure as well as
is a function of the volume flow
inter-pump spacing, and the
rate Q and documented in the
distance e1 between the rear
type series booklet.
wall and the pumps’ centreline.
Thanks to its channel impeller
Fig. 2.2.6-a offers basic guid-
~ 1.6 to
The lateral distance smin ~
this pump type is relatively
ance for a pump installation
1.8 x D should be also observed.
straightforward with regard to
concept.
the pump station design.
For discharge tubes with a diam-
Amacan K pumps can be in-
The following conditions should
eter of D = 700 a factor of 1.6
stalled into the discharge tubes
be assumed as reference values
and with D = 1400 a factor of
with no need for any special
for a preliminary concept:
1.8 must be applied. Other inter-
intake chambers or separating
walls between the pumps. To
rule out any possibility of the
mediate values must be estabObserving the rear wall
~ 0.6 x D is crucial.
distance e1 ~
pumps influencing each other,
lished through interpolation.
Flow straighteners as used for
Amacan P or Amacan S are not
it is, however, important to ob-
The required minimum water
serve the required installation
level t1 – as is also the case with
distances: the lateral distance
the other submersible pumps
Where inflow angles differ and
between the pump and the
installed in discharge tubes –
flow velocities are higher than
required.
1 m/s, it is necessary to take
e1
measures suited to deal with
that specific intake situation
(see section 2.3 “Pump sump
design”).
S1/2 min
Recommended
inflow
0-45˚
Vmax = 1 m/s
S1 min
S1 min
Fig. 2.2.6 -a: Minimum dimensions
29
2.3
Pump sump design
Wrong
D
2.3
Pump sump design
Vortex
> 8˚
The fluid storage space or the
pump sump connects the pump
station intake with the submersible pump in the discharge
tube. There are as many vari-
Correct
D
ations in the design of this part
approx. 4 to 5 D
of the intake structure as there
are pump installation options.
Only a few examples can be
max. 8˚
looked at in the following
chapter; the dimensions in the
drawings refer to these cases
only. If project or modification
Fig. 2.3-a: Shape of sump floor
conditions deviate from the
examples described here, we
When the flow enters the pump
recommend consulting KSB.
station structure from a channel,
either a diffuser-type enlarge-
One feature of an optimum
ment (number of pumps n +
pump sump design is that there
chamber width x n+ (n –1) x
are no major steps or slopes
wall thickness) or a so-called
with an inclination of more
curtain wall is required. Which
than 8 degrees on the sump
of these measures is appropriate
floor. A distance of at least 4 to
for the project in hand, must be
5 D (D = discharge tube diam-
individually decided upon.
eter) should be maintained from
the last point of disturbance or
floor alteration to the pump
centreline. Higher steps or
slopes (> 100 mm) should be
v in = 1.2 m/s
(max)
Floor gradient
8˚ max.
avoided at all costs in order to
prevent submerged areas of flow
15˚ max
0.3 to 0.5
m/s max
separation and floor vortices.
Fig. 2.3-b: Maximum permissible divergence
angle for flow cross section and permissible
velocities according to HI [5] and SN [12]
30
2.3
Pump sump design
While some sources give details
If the direction of the flow
in the direction specifically re-
of installations where submers-
(relative to the orientation of
quired. The result is a symmet-
ible pumps in discharge tube
the pump intake chamber) dis-
rical approach flow into the
design do not have their own
charged from the inlet channel
pump chambers. If such a wall
intake chambers, KSB, in con-
changes, this must be corrected
is not installed, the energy
trast, believes that each pump
by appropriate devices, so-called
contained in the flow may cause
should be provided with its
“flow straighteners”. While one
vortices; in addition, as shown
own, fully shaped intake
function of flow straighteners is
in Fig. 2.3-c, the flow to the
chamber (see sections “Open
to dissipate the kinetic energy
chambers is asymmetrical and
intake chamber” to “Covered
of the fluid entering the pump
therefore detrimental to
intake chamber”) in order to
station, their opening towards
trouble-free pump operation.
rule out any possibility of the
the floor ensures the flow moves
pumps influencing each other.
Actual inflow conditions are
difficult to predict, as vortices
may form even in the case of
1.3-1.4 x D z
Dz
low pump flow rates as a result
of various influences in the
intake structure or the pump
stations’s mode of operation,
0.1 x D z
0.45 ... 0.6 x D z
with the accompanying negative
effects on the pumps.
l min
e1
D
According to KSB, flow velocities of no higher than 1 m/s are
b
permitted for the intake chamber geometries specified in the
type series booklets. Therefore,
with a view to reducing the
intake building structure, it is
necessary that the conditions
>
_ 3.5 x D
around the pump are optimally
designed to avoid problems.
>
_5xD
Fig. 2.3-c: Example of a pump station with
cross flow and curtain wall
31
2.3
Pump sump design
If the difference in height between the inlet structure and
the pump sump is large it may
D
be necessary to eliminate the
risk of aeration by incorporat-
H min
ing a weir-type structure. A
150 mm
difference in height of more
than 0.3 m [7] already provides
sufficient reason to take
appropriate measures. The
adjacent illustration shows a
pump station with a considera-
D
ble difference in height between
Entrained
air bubbles
the inlet channel and the pump
sump and how this problem has
been solved by fitting appropriate structures in the sump.
Changes in flow direction can
also be expected if only a few
pumps are operating in a mul-
Fig. 2.3-e: Pump station with weir-type
structure
tiple-pump system. Here preliminary assessment of the
If a divergence angle of more than
situation could help to decide
15 degrees is planned in the build-
whether a covered intake cham-
ing to reduce inflow velocity vi ,
ber should be preferred to an
additional steps such as the in-
open one.
stallation of flow distributors
and/or baffles are necessary to
prevent vortices caused by flow
separation. The feasibility of
these measures depends on the
nature of the fluid pumped.
Flow distributors
20
On
Baffle columns
On
v
v
v
On
Off
v < 0.5
m /s
Fig. 2.3-d: Flow pattern developing
with variable pump operation
32
α > 15˚
Fig. 2.3-f: Flow optimisation
α > 15˚
2.3
Pump sump design
The intake situation from a
If the fluid is taken from stag-
channel is comparable with the
nant waters, then cross flow is
abstraction of water from a
irrelevant. If the fluid level
river. Depending on the flow
above the pumps is sufficient
velocity, areas of flow separa-
for the respective volume flow,
tion can be expected where the
i. e. a minimum water level t1
water flows into the intake
between the lowest water level
chamber area. If it is not pos-
in the water body and the in-
sible to provide a covered intake
take chamber floor can be
chamber, then it is important to
assured (see type series book-
markedly extend the chamber
lets), it is no problem to use
walls. As a reference value the
open intake chambers.
pump station designer can as-
Depending on the design of the
sume a factor 3 relative to the
pump station’s lateral walls, it
dimension L min given in the
may be possible to make them
technical literature.
slightly longer than the intake
chamber wall in order to reduce
the influence of flow deflection
on the outside intake chambers.
Fig. 2.3-g: Pump station with
open chamber for water abstraction from a river
Fig. 2.3-h: Pump station with
open chamber for water abstraction from stagnant waters
33
2.4
Solutions for special cases
2.4
Solutions for special
cases
To define these special cases
The extent to which such
more clearly, a few criteria, like
measures are to be verified by
for instance the maximum vel-
model tests or CFD (Compu-
ocity in the approach zone of
tational Fluid Dynamics)
If standard intake structures
v > 1m/s and the large cross
simulations should be indi-
cannot be realised or the con-
flows potentially associated
vidually determined.
ditions in the pump station do
with them must be mentioned.
not correspond with the above
In such cases precisely dimen-
mentioned layouts, KSB’s
sioned baffling and specially
expertise should be utilised to
dimensioned intake chambers
find specific design solutions.
could possibly help to optimise
The sooner advice is sought in
the approach flow to the pump.
such special cases, the better –
The nature of the fluid pumped
and the higher the chance of
is here again crucial, thus under-
identifying potential problems
scoring the need for an indi-
and of taking appropriate
vidually engineered solution.
measures to find a practical
KSB has numerous successful
solution.
designs in this field to its credit.
Fig. 2.4 -a: Specially dimensioned intake chamber
for cross flows of v = 1,8 m/s
34
2.5
The necessity of model testing
2.5
The necessity of
model testing
The object of these tests is to
The dimensionless numbers
REYNOLDS number
Re =
FROUDE number
Fr =
It helps identify precisely where
problematic conditions (vortex
station building deviates from
proven layouts as regards
simulate the flow of a planned
pump station in a scale model.
- The concept of the pump
applied here are as follows:
WEBER number
action, uneven velocity distri-
vd
ν
v
√g.d
ρ .v 2 . d
We =
σ
bution, etc.) might arise and
how to then influence these
positively, where necessary.
The high transparency of
acrylic glass makes this material an excellent choice for the
construction of suitable models.
chamber dimensions, piping
layout, wall spacing, considerable changes in flow direction between inflow into
the building and the approach
flow to the pump, etc.
- The volume flow rate per
where:
v = flow velocity in m/s
d = hydraulc diameter in m
ν = kinematc viscosity in m 2 /s
g = gravitational constant in m/s2
σ = surface tension in N/mm 2
pump is higher than 2.5 m3 /s
or 6.3 m3 /s for the entire
pump station
- The inflow is asymmetrical
and/or not uniform
In order to be able to tranfer
As these characteristics are to a
- Alternating pump operation
the flow conditions to the full-
degree interdependent, it is im-
in multiple-pump stations
size structure, dimensionless
possible to apply them at the
involves significant changes in
numbers are applied in the
same time in a scaled model.
flow direction
design of the model. These
It is therefore important to find
characteristic coefficients de-
a compromise which helps
scribe the forces acting in the
achieve the optimum for a given
flow; they should be as identical
application.
- An existing pump station has
already created problems.
as possible for both the model
and the full-size structure. The
Model testing is absolutely ne-
most relevant forces are gravity,
cessary when one or more of
as well as those resulting from
the criteria listed below apply to
dynamic viscosity, surface
the intake structure or pump
tension and the inertia of the
sump:
fluid in motion.
35
2.5
The necessity of model testing
Test set-up
Instead of an impeller a vorto-
The surface vortices are classi-
The geometry of the model
meter is employed whose rota-
fied according to Hecker in six
must correspond with the
tional speed provides information
categories (1 = low, 6 = very high)
original structure, taking into
on the development of vortices
and the submerged vortices in
account the selected scale and
in the intake.
three or four categories according
the characteristic coefficients
to Tillack [16].
mentioned previously. This
The flow velocities are meas-
applies to the hydraulic part of
ured at reference points across
the building structure and the
the model pump’s entire suction
pumps. Both the structure of
cross section via Pitot tube or
the building and the pumps are
laser. To judge vortex develop-
constructed from transparent
ment the fluid surface as well as
material. A model of the
the wall and floor areas are
impeller is not required as the
observed. Vortex intensity in a
test aims to simulate only the
given flow cross section is
flow approaching the impeller.
visualised by means of dyes
while their size is measured by
the swirl angle of the
vortometer. The following
equation is applicable:
Θ = tan -1
Fig. 2.5-a: Acrylic model of an
Amacan P pump station
Type 1
Type 2
Type 3
Slight surface swirl
Surface swirl with
dimple
Intense surface
dimple whose core
can be seen (dye)
Type 4
Type 5
Type 6
Vortex dimple
entraining contaminants below the
water surface
Vortex pulling air
bubbles to the pump
intake
Full air core
reaching to pump
bellmouth
Fig. 2.5-c: Classification of
surface vortices according to
Hecker (Types 1 to 6 )
(π°du n )
m
where:
d m = pipe diameter
Type 1: Slight swirl at floor or wall
Type 2: Vortex at floor or wall
Type 3: Air-entraining vortex
at floor or wall
Type 4: Vortex at floor or wall
with vapour core
(here the pump´s suction pipe)
n = rotations of vortometer
u = axial flow velocity
Fig. 2.5-b: Vortometer
36
Fig. 2.5-d: Classification of
submerged vortices according to
Tillack (Types 1 to 4 )
2.5
The necessity of model testing
If one were only to look at the
Evaluation of results
In general the following applies:
diagrams, these vortex
Before the design is finalised
Occurrences that have a minor
formations appear relatively
the measurement results should
effect in the model may be con-
harmless. Vortex formation
be confirmed by all parties
siderably more significant in
observed in model tests give an
involved: pump station designer,
the full-scale structure!
idea of what could happen in a
end user, pump manufacturer
real structure. Unlike laboratory
and the institution which con-
The tests must be concluded
situations a real pump station
ducted the tests.
with a detailed report on the
operating conditions investi-
rarely deals with clear water
and it is difficult to identify
Main criteria:
and operating conditions ob-
vortex action as the source of
problem, especially when submerged vortices are involved.
1. The mean flow velocity at
served (for the tested water
the defined measurement
levels in the building structure)
points of the suction cross
have to be documented on
section should not deviate
video tape and made available
from the mean value by
to the party commissioning the
more than 10 %.
tests.
2. The swirl angle should not
Fig. 2.5-e: Laboratory photo of a
surface vortex type 6
gated. The vortex formations
KSB will support and co-ord-
be higher than 5 degrees.
inate project related model tests
A swirl angle of 7 degrees
upon request.
can be tolerated if it has occurred during less than 10 %
of the period of observation
or if the pump manufacturer
has defined other limits.
3. Surface vortices may only be
accepted up to type 2 and
submerged vortices up to
Fig. 2.5-f: Laboratory photo of a
surface vortex type 3
type 1 if they do not have
an unacceptable influence
on the measured velocity
The criteria which apply to this
profile.
method of investigation may
vary slightly depending on the
type of pump or size of station.
37
2.6
The significance of CFD simulations
2.6
The significance of
CFD simulation
Methodology
The mathematical description
of fluid flows is based on the
NAVIER-STOKES equations.
Numerical flow simulation
They describe the processes at
(Computational Fluid
each point of a flow by means
Dynamics = CFD) is becoming
of partial differential equations
increasingly important. The
for the mass, energy and mo-
software specially developed for
mentum.
this purpose is an effective
instrument allowing relatively
precise predictions of the flow
1 ∂p
∂u
∂u
∂u
∂u
+u
+v
+w
+v
= fx _
ρ ∂x
∂t
∂x
∂y
∂z
[ ∂∂xu + ∂∂yu + ∂∂zu ]
1 ∂p
∂v
∂v
∂v
∂v
+u
+v
+w
+v
= fy _
ρ ∂y
∂t
∂x
∂y
∂z
[ ∂∂xv + ∂∂yv + ∂∂zv ]
conditions. The time and cost
of flow modelling depends on
the
- size of the flow area to be
modelled
2
2
2
2
2
[
- computer performance
The calculation of each spatial
- form of presentation of
point in a flow is not feasible as
results (report) and scope of
this would result in an infinite
results.
number of calculations. A grid
is generated instead and its nodes
are calculated. The grid model
is then processed further to
provide information on the pressure and velocity distribution,
which can then be subjected to
numerical and/or graphical
analysis. In modelling, the distances between individual nodes
38
2
2
2
2
2
2
1 ∂p
∂w
∂w
∂w
∂w
∂ 2w ∂ 2w ∂ 2w
+u
+v
+w
+v
+
+
= fz _
ρ
∂z
∂t
∂x
∂y
∂z
∂ x2 ∂ y2 ∂z2
- desired geometric resolution
Fig. 2.6 -a: Flow patterns in
Amacan intake chambers
2
may partly differ; they depend
on the flow velocity gradients.
]
2.6
The significance of CFD simulation
The calculated nodes lie closer
Problems are more often caused
together near walls and corners,
by the fact that surface and
which are considered as discon-
submerged vortices and asym-
tinuities from a fluid dynamics
metrical inflows do not always
point of view. In areas with low
exhibit steady behaviour and
velocity gradients it is not a
are therefore difficult to predict
problem to increase the dis-
exactly.
tances. In addition, assumptions
on the distribution of turbulence are made at the nodes.
The task of a CFD specialist is
to choose the “correct” turbulence model. It takes a lot of
experience to be able to create
an adequate model and to be
able to accurately interpret the
Fig. 2.6-c: Simulation of pump
station with several pumps
results obtained.
At KSB CFD simulation is a
well-established engineering
tool that has been used for
years. The fact that CFD
calculations have been proven
to conform well with model
testing in past investigations
Fig. 2.6 -b: Simulation of approach
flow to discharge tube
allows more accurate predictions to be made today on
potential flow situations and
CFD simulation is perfectly
enables pump stations to be
suited to evaluating flows in
more systematically optimised.
intake structures and pump
In complicated cases, however,
sumps, especially as it can also
physical model testing is to be
be used to make a very exact
preferred to CFD calculations
analysis of the influence single
for building structure
pumps have on the flow pattern
investigations.
in multiple-pump systems.
In the future the use of both
CFD simulations and model
testing will significantly reduce
the overall costs of pump
station investigations.
39
2.7
Screening equipment
2.7
Screening equipment
Under conditions of long-term
account that a screen filled with
operation, however, failure to
trapped material creates flow
fit the appropriate screening
resistance resulting in different
The installation of screening
equipment upstream of a pump
water levels up- and downstream
equipment is required for
station will lead to sand accu-
of the screen. This means that
trouble-free pump operation:
mulation and considerable sedi-
the water level downstream of
Depending on the type and
mentation in stagnation zones
the screen must not fall below the
origin of the fluid handled it is
at and within the building, as
permissible minimum water level
desirable to install coarse
well as in increased wear to
t1 for the pump’s operating point.
screens (the distance between
centrifugal pumps. Also, mechan-
bars should be between 5 and
ical damage to the impeller and
30 cm) and/or fine screens (the
other pump parts cannot be
distance between bars should
ruled out.
be between 5 and 20 mm) as
well as shingle traps, mounted
Where the screens are to be
upstream of the screens, if
accommodated in the pump
needed. The screens and traps
station concept is the designer’s
should be cleaned automatically
decision. The screening equip-
during pump operation using
ment is either mounted upstream
appropiate mechanical equip-
of the pump station or sump to
ment. In applications where
prevent coarse material from
surface water from rivers, lakes
entering the building, or single
and channels is pumped or in
screens are directly integrated
storm water pumping stations
into the intake chamber design.
the installation of screening
Selecting the latter option may
equipment is an absolute must.
necessitate longer chambers due
Fig. 2.7-b: Screens with automatic
cleaning devices
to the slightly reduced flow cross
section which results from integrating the screen. Downstream
of the screening equipment the
velocity distribution developing
across the flow cross section
Fig. 2.7-a: Coarse screens upstream of an Amacan pump station
(water abstraction from a river)
Fig. 2.7-c: Shingle trap upstream
of pump station
should be even and therefore
Half of the impeller free passage
favourable for pump operation,
should be used as a reference
provided the screen is largely
value to determine the permis-
free from any trapped material
sible maximum distance between
(see Fig. 2.7-b).
the screen bars. This value can
be taken from the appropriate
The fact that river water in particular contains shingle and
When establishing the minimum
pump curve (see the type series
sediment is often overlooked.
water level t1 in the pump sump,
booklet or selection software).
it is also necessary to take into
40
2.7
Screening equipment
horizontal position, the correc-
The following values can be
tion factor for the cleaning
applied for the following dif-
method csc and the coefficient
ferent bar shapes:
ζsc. For a clean screen this correction factor is 1, with mechanical cleaning it ranges between
Shape
1
2
3
4
5
6
7
ß sc
1
0.76
0.76
0.43
0.37
0.3
0.74
1.1 and 1.3 and with manual
Fig. 2.7-d: Wood inside the diffuser casing of an Amacan pump
cleaning between 1.5 and 2. The
coefficient ζsc includes the shape
of the screen bars and the area
To evaluate the screen’s influence on the water level directly
upstream of the pumps it is ad-
ratios between the free flow
area a– and the distance between
–
the bar centrelines b.
visable to use Hager’s simplified
calculation [10], if a detailed
.
screen selection procedure is
.
not being undertaken.
–a
.
vo
–
b
.
.
ΔH
δ sc
Fig. 2.7-e: Flow through screen,
without lowered floor
Fig. 2.7-f: Screen layout drawing
Therefore,
ξ sc = β sc x ζ sc x c sc x δ sc
Applying this calculation will
1
result in the lowering of the
2
4
3
screen as expressed in the
–
L
–
0,6 L
water level downstream of the
6
5
7
–
0,3 L
vo
equation:
–
d
v2
ΔH = ξ sc x 0
2g
Here v0 is the flow velocity up-
Fig. 2.7-g: Different shapes of screen bars
stream of the screen. The total
loss coefficient β sc is a function
of the angle of inclination of the
screen δ sc in relation to the
41
2.7
Screening equipment
–
L is the length of the sreen bar
–
profile and a the width. If the
– –
ratio of L / a is 5 and the
condition
b
a
> 0.5 is satisfied,
For detailed screen selection, the
take chamber area would then
method according to Idelchik
achieve a better defined and
[11, p. 504 ff] is recommended:
even approach flow condition
This method is most appropriate
for the pump and screen.
the formula for ξ sc can be
simplified and expressed as
when the influence of oblique
flow to the screen is also to be
Cleaning of the screen should
follows:
taken into account or if the
preferably take place automat-
screen bars are markedly differ-
ically. To activate the cleaning
ent from what was illustrated in
process it is possible to make
Fig. 2.7-g.
use of the difference in water
ξ sc =
7
β x
3 sc
3
–
4
[ ab −1]x c
sc
x sin δ sc
levels up- and downstream of
In order to compensate for the
the screen. This ensures that the
losses ΔH occurring as the flow
cleaning process is activated as
passes the screen, the floor of
required. Manual cleaning is
the intake structure or channel
unfavourable for pump systems
is often lowered by the value Δz
in continuous operation, as the
downstream of the screen.
water level has to be regularly
checked and the screen cleaned
ΔH = Δz
Fig. 2.7-i: Pump station with
automatic screens
The values usually applied for
Screens are often integrated in
between approx. 5 cm for
the direct vicinity of the intake
mechanical cleaning to approx.
chambers. This means every
10 cm for manual cleaning.
pump is dedicated with its own
screen. The distance between
the screening equipment and
the pump’s discharge tube
should be at least 4xD (D being
vo
the discharge tube diameter).
Δz
If it is assumed that the flow
might approach the screen from
Fig. 2.7-h: Flow through screen
with lowered floor
the side and the influence on
the water level downstream of
the screen might be difficult to
predict, preventive measures are
then advisable. Extending the
intake chamber wall and
positioning the screen in the in-
42
controlled cleaning is also not
sufficiently reliable.
losses through screens range
ΔH sc
by the operating staff. Timer
3.1
Discharge tube designs
3.
Discharge tube
designs
The design configuration of
Amacan pumps allows a wide
3.1
Design variants
For this variant it is necessary
that at the upper building level
variety of installation variants
the discharge tube is appropri-
to be chosen with practically
ately sealed against the fluid
no boundaries set on a designer’s
pumped and supported to
creativity. Discharge tubes are
withstand the mechanical forces.
not only made from metal ma-
The upper discharge tube edge
terials - they can also be con-
has to be designed in accord-
structed with concrete elements.
ance with the run-off conditions
No matter which installation
of the discharged fluid and the
variant is chosen, it is impor-
H min
tant that the pump’s support
maximum flow velocities within
the tube itself.
area in the tube, shaped as a
45-degree slope, is executed
accurately.
Fig. 3.1-a: Installation type A
The support ring is set in concrete in the intake chamber
H min
area, then the concrete tube
elements are used to construct
the discharge tube. Such a
design variant may be suitable
for use in simple drainage and
Fig. 3.1-c: Installation type BU
irrigation pump stations.
This discharge tube variant can,
of course, also be employed in
conjunction with open intake
chambers. The final decision on
the intake chamber design is
H min
taken on the basis of the required
minimum water level relative to
the volume flow rate of the pump
and the approach flow direction
(see diagram t1 = f(Q) in the
Fig. 3.1-b: Installation type BG
type series booklet or selection
software).
This illustration shows a covered
intake chamber.
Here the discharge tube is, however, made from metal.
43
3.1
Discharge tube designs
mounted, the installation area is
closed with a cover suitable for
vehicles. The electrical cables
3.2
Details on discharge
tube design
are routed under the floor to the
H min
power supply.
The manufacturing quality of
the discharge tube is important
for the proper functioning of
the pump or pump station. As
the pump is centered and pos-
Fig. 3.1-d: Installation type CG
itioned in the discharge tube on
The next type of installation
a 45-degree bevel, resting on a
presented here is the underfloor
rubber ring provided at the
installation. The horizontal
H min
pump casing (the pump is seat-
discharge pipe outlet is situated
ed by its own weight plus the
below the upper building level.
axial thrust developed during
An additional, above-floor
pumping), particular attention
building structure, which is
necessary in conventional pump
Fig. 3.1-f: Installation type DU
must be given to this area
during manufacturing. Poor
stations, is not required here,
If some systems require the
concentricity and surface finish
resulting in a cost advantage.
discharge flange to be connected
may cause the pump to rest on
above the floor, the installation
some points but not all of the
type illustrated in Fig. 3.1-f can
inclined support area, resulting
be chosen. A plate is mounted
in inadequate sealing with some
on the upper building level to
flow passing back to the suction
accommodate the discharge tube
side. As a consequence, the
forces. When deciding on the
pump does not achieve the
size of this plate it is important
volume flow rate required for
to consider the maximum forces
the connected system.
H min
developing during pump operation (pump weight, piping
forces, torques resulting from
Fig. 3.1-e: Installation type CS
pump operation, etc.).
If the area above the pump
station is intended for vehicular
traffic, the discharge tube can, if
necessary, be fitted with support
feet resting on the floor underneath the inlet. After the discharge tube has been set up and
44
Fig. 3.2-a: Support area of pump
in discharge tube for Amacan K
3.2
Discharge tube designs
For all discharge tubes closed
low wall thicknesses the natural
with a cover it is vital to provide
frequency of the tubes may
an adequate venting device. If
quickly reach excitation fre-
this is not provided, a cushion
quency levels (owing to the
of compressed air will develop
working principle of the centri-
in the upper discharge tube
fugal pump). The result is res-
section. This has an effect
onance accompanied by extreme
similar to that of a spring and
vibration effects.
prevents the pump from running
steadily. In extreme cases,
Foundation bolts at site
affect the entire discharge tube.
If the tube is a welded metal
of the tube down to the sump,
sheet construction, it is import-
or the discharge tube cover is
ant to ensure that the welded
fitted with a venting and aer-
seams in the 45-degree support
ation device. If a vent pipe is to
area are level and true. The
be fitted, the additional space
entire discharge tube should
required must be taken into
additionally be checked for
account when planning the ac-
concentricity. As thin metal
cess openings.
.
Fig. 3.2-b: Discharge tube in
sheet metal construction for
Amacan P / S
.
vibrations may be caused which
pipe is laid from the upper end
.
.
.
.
As a remedial measure, a vent
Adapt to site conditions
( ≈ 400)
Fig. 3.2-d: Discharge tube bracing
with turnbuckles
sheets tend to be deformed by
the welding process the metal
sheet thickness should not be
less than 8 mm.
Alternatively, it is also possible
to make this support area as a
turned part and to weld it to
the discharge tube at the top
Fig. 3.2-c: Discharge tube fitted
with valve for venting and aeration
and bottom. Making long discharge tubes from individual
If the installation depth of the
segments bolted together at
discharge tube is more than
their respective flanges is rec-
4 metres the tube should be
ommended to improve concen-
centered and/or braced. This is
tricity. These tubes are easy to
particularly important in the
install at site and the flanges
case of stainless steel tubes
provide additional mechanical
which are used for their rela-
stability in the radial direction.
tively thin walls. Due to these
45
3.3
Cable connections
3.3
Cable connections
This sealing principle is used
the form of the discharge tube
for both power and control
and the system pressure. If the
cables. When the pump is in-
tube variant is one closed with
The pumps of the Amacan series
stalled in the discharge tube, it
a cover, the cables must be
are all equipped with an abso-
is necessary to mechanically
supported by a separate holder
lutely watertight cable entry
support the cables’ own weight
underneath the cover to support
system. This KSB patented
and at the same time protect
the cables’ own weight and pro-
system protects against the
them against flow turbulence.
tect them against flow turbu-
pumped fluid penetrating the
For this purpose KSB has de-
lence in the discharge tube, as
motor space or terminal box of
veloped a patented cable holder.
described above.
the pump if the cable insulation
The cables (power and control
has been damaged during
cables) are attached to a stain-
assembly or operation. The
less steel carrier rope using
insulation of the individual
rubber profiles and a clip. The
cable cores is stripped and the
rope is then screwed to the dis-
wire ends are tinned. This sec-
charge tube cover or to a cross
tion is fixed in the cable gland
bar in the case of an open dis-
system with spacers and then
charge tube. This guarantees
embedded in synthetic resin. A
that the cables have a long ser-
rubber gland provides additional
vice life and the cable entry into
sealing.
the motor housing is absolutely
tight.
Fig. 3.3-c: Cable suspension and
cable entry into discharge tube
If the discharge tube is open, the
1
cables are routed vertically out
2
of the tube and are then attached
to a cross bar. If Amacan pumps
3
4
1 Long rubber gland
2 Outer cable insulation
3 Individual cores are additionally cast
in resin
4 Individual core insulation stripped, wire
ends tinned and embedded in cast resin
Fig. 3.3-a: Sectional drawing of an
absolutely watertight cable entry
system on a pump
46
Fig. 3.3-b: Example of a rope with
cable holder for an installation
depth of 50 m
are installed at greater installation
depths, then additional supports
should be fitted to hold the cable
carrier rope in position. The
To ensure the cables are smoothly
object of these supports is to re-
routed through the discharge
duce the influence of the turbu-
tube cover either welded-in
lent flow on the rope. These
sleeves or shaped rubber gromets
supports rest against the dis-
are used. The choice of cable
charge tube wall.
passage depends in the main on
3.3
Cable connections
If the components described
above are not ordered along
with the pump, other solutions
may have a very negative influence on the pump’s functioning. Power and control
cables are, for instance, very
Fig. 3.3-d: Supports for cable
guidance in the discharge tube
often attached to the rope with
simple cable straps; this, however, will lead to the destruction
When ordering the pump it is
of the cable insulation and/or
necessary to specify the exact
core breakage inside the cable
installation depth so that the
during pump operation.
precise length of the cables and
ropes as well as the number of
supports can be determined. If
the specifications of both planning and execution stages differ,
the following two situations
may arise: If the rope is too
short, the pump will not be
firmly seated in the discharge
tube and the reaction moment
Fig. 3.3-e: Cable attachment using
simple cable straps
of the pump may damage the
cables during start-up. If the
For installation depths greater
cables are too long or not tight
than 5 m the cable holder and
enough, the flow may cause the
carrier rope design becomes
lifting rings of the cable assembly
increasingly important for
to hit against the discharge tube
trouble-free pump operation.
thereby damaging discharge
tube, rope and cables.
In order to determine the correct number of lifting rings on
the rope, it is also important to
know the lifting height of the
davit, lifting frame or crane.
47
4
List of references and photographs
4.
References
[1]
Dr.-Ing. K. Holtzenberger, KSB AG, Centrifugal Pump Design, 5th edition 2005,
ISBN 3-00-004734-4
[2]
KSB AG, Amacan P type series booklet, 1580.5/5
[3]
KSB AG, Amacan S type series booklet, 1589.5/5
[4]
KSB AG, Amacan K type series booklet, 1579.5/3
[5]
Hydraulic Institute, American National Standard for Pump Intake Design, ANSI / HI 9.8-1998
[6]
M. J. Prosser, The Hydraulic Design of Pump Sumps and Intakes, BHRA, July 1997
[7]
Henry T. Falvey, Air-Water Flow in Hydraulic Structures,
Engineering and Research Center Denver, Colorado 80225, December 1980
[8]
Jost Knauss, Swirling Flow Problems at Intakes, IAHR+AIRH, ISBN 90 6191 643 7, Rotterdam 1987
[9]
Christian Frey, Peer Springer, Dr. Sven Baumgarten, Bernd Kothe, Optimization of Waste Water
Pumping Station Architecture Using CFD Analysis, Validated by Model Testing,
Pump Users International Forum 2004, Section 5: Pumps for Waste Water, Karlsruhe, Germany
[10]
W.H. Hager, Abwasserhydraulik: Theorie und Praxis, Springer Verlag, ISBN 3-540-55347-9, 1994
[11]
I.E. Idelchik, Handbook of Hydraulic Resistance, 3rd Edition, Research Institute for Gas Purification,
Moscow 1994, ISBN 0-8493-9908-4
[12]
Schweizer Norm SN CR 13930: Rotodynamic Pumps – Design of Pump Intakes –
Recommendations for the Installation of Pumps, VSM 2000
[13]
Charles E. Sweeney, Rex A. Elder, Duncan Hay, Pump Sump Design Experience: Summary, March 1982
[14]
US Army Corps of Engineers, Pumping Station Inflow – Discharge Hydraulics, Generalized Pump Sump
Research Study, Technical Report HL-88-2
[15]
Robert Sanks, Pumping Station Design, 2nd Edition, Butterworth Heinemann, Boston · Oxford ·
Johannesburg · Melbourne · New Delhi · Singapore
[16]
P. Tillack, D.-H. Hellmann, A. Rüth, Description of surface vortices with regard to common design
criteria of intake chambers, 2nd International Conference on Pumps and Fans, Beijing, China 1995
Photographs
Pg. 15 Fig. 2.1-a : KaiserslauternTechnical University, Institute for Fluid Machinery
Pg. 23 Fig. 2.2.4-i : Hydrotec Consultants Ltd., Leeds, UK
Pg. 37 Fig. 2.5-e and 2.5-f : KaiserslauternTechnical University, Institute for Fluid Machinery
Author
Dipl.-Ing. Bernd Kothe, born in 1955, studied at the Otto von Guericke Technical University in Magdeburg.
After completing his studies, he became a development engineer for power station pumps at the Pumpenwerke
Halle (Saale) company. From 1993 to 1998 he was responsible for transient flow analysis and complex waste
water calculations in the engineering department of KSB AG. Since 2002, he has held the position of Sales
Support Manager of the Competence Center Waste Water in Halle (Saale), Germany.
48