[New Products & New Techniques]
Model CB Double Suction Pump for the Global Market
Takayuki MIYAMOTO*, and Soichiro OGAWA*
Abstract
As key products for the global market, Ebara has released model CB double suction pumps. This model can be used in a wide
variety of industries, such as public water supply, general water supply and conveyance, cold/hot water circulation, building
facilities, general industries, power plants, petroleum plants, and gas plants. Thanks to the new, high-efficiency flow passage,
which Ebara developed through DOE (design of experiments) and sensitivity analyses, the pumps meet an energy efficiency
value of η3 in China’s GB standards. In addition, the optimal design of their casing and rotor parts has reduced their pump
weights.
Keywords: Double suction, Centrifugal pump, High efficiency, Weight saving, GB standards, Energy saving, Stress analysis,
Contact analysis, Through bore, Shortening bearing span
1. Introduction
using a correction coefficient, the required efficiency is
Regulations concerning energy conservation have been
determined for each classified pump. There are three
expanding in global markets. Especially in China where
levels of required efficiency: η1, minimum allowable value
markets continue to grow, the efficiency regulation of
of energy; η2, target minimum allowable value of energy;
pumps is stipulated in China’s GB standards (hereafter
and η3, evaluating value of energy conservation. η1
GB standards) . GB standards are divided into
represented the required efficiency until the end of
mandatory standards (GB), which are enforceable by
June 2011. η2 has represented it since the beginning of
law, and recommended standards (GB/T). In terms of
July 2011.
1)
land centrifugal pumps, GB standards not only request
η3 presents the highest efficiency. If a product meets
that manufacturers produce products with a specified
η3, it can obtain certification as an energy conservation
level of efficiency, but also encourage them to develop
product in China. Thus, users can select highly efficient
products that satisfy stricter energy conservation
products more easily.
standards according to“the minimum allowable values
Unfortunately, conventional model CNC pumps that are
of energy efficiency and evaluating values of energy
sold in China have not yet metη3. It is very challenging
conservation of centrifugal pump for fresh water”
for these products to improve their efficiency enough to
(GB19762-2007).
attain η3.
For land pumps, fluid is limited to fresh water. Three
Ebara Corporation and Ebara Machinery (China) Co.,
types of centrifugal pumps (end suction single stage,
Ltd. (hereafter EMC) have jointly developed model CB
double suction single stage, and multi-stage) are
pumps by fully remodeling conventional models
classified according to flow rate and specific speed. By
(Figure 1). Thanks to the new, high-efficiency flow
passage2), all model CB pumps meet η3. In addition, the
optimal design of their casing and rotor parts has
* Fluid Machinery & Systems Company
reduced their pump weights.
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Ebara Engineering Review No. 256 (2018-10)
Model CB Double Suction Pump for the Global Market
Volute loss
High
flow
Low
Cross-section A
(a) Conventional model
Fig. 1
Model CB double suction pump
flow
This paper will provide an overview and introduce
features of model CB double suction pump for the
Cross-section B
Global Market.
(b) Optimized shape model
Fig. 2
2. Features
Examples of flow analysis
Figure 1 shows the model CB double suction pump.
In this chapter, we compare features of conventional
model CNC with those of new model CB.
streamlines was reduced. Also, since the secondary
flow was smaller than that at cross section A of the
conventional model, the loss was smaller.
2.1 High efficiency
In order to meet η3, an evaluating value of energy
2.2 Weight saving
conservation, the new, high-efficiency flow passage has
In order to reduce costs, the weight of the casing was
been employed. The impeller, discharge volute, and
reduced and the rotor parts were optimized, compared
suction flow passage, which make up the flow passage,
with those of the conventional model. Details are shown
were designed with optimal design parameters
below.
obtained through design of experiments and sensitivity
2.2.1 Casing weight reduction
Since the casing accounts for about 50 % of the mass of
analysis, to achieve high pump efficiency.
Figure 2 shows results of steady flow analysis of
a pump, we focused on optimizing the wall thickness.
discharge volutes. The contours in Figure 2 shows the
A pressure test with water is usually carried out
all pressure loss distribution of the discharged volutes,
before a performance test. The casing must maintain
where increases in red indicate greater pressure loss,
pressure as a pressure vessel without leakage and
while increases in blue indicate smaller pressure loss.
plastic deformation.
When the conventional model and the optimized shape
Figure 3 shows the result of stress analysis at a
model were compared, it was found that the pressure
pressure of 2.4 MPa (1.5 times the maximum operating
loss was reduced in the volute of the optimized shape
pressure of 1.6 MPa). An optimal wall thickness was
model because the volute had more blue areas than
determined so that the maximum principal stress of
that of the conventional model.
the casing was smaller than the yield stress.
The three-dimensional streamlines (the solid lines in
Figure 4 shows the results of surface contact
Figure 2) were drawn from where the pressure loss at
analysis. The red parts represent contact surfaces, and
the cross section indicated by an arrow was large. In
the green parts indicate the gap between the upper
the optimized shape model, the deviation of the
and lower casings. We learned that there was no
─ 2 ─
Ebara Engineering Review No. 256 (2018-10)
Model CB Double Suction Pump for the Global Market
Maximum principal
stress
High
Clamped
Shaft
Low
Key insertion section
Fig. 5
Fig. 3
Torque
Example of stress analysis of shaft
Example of stress analysis of model CB casing
Clamped
Gap
0
Max
Fig. 4
Torque
Example of surface contact analysis of model CB casing
leakage because the gap did not reach any bolt hole.
Plastic deformation and leakage did not occur, even
Fig. 6
in a pressure test with an actual machine. Accordingly,
concerns about insufficient strength and leakage in a
3. Product Overview
pr es s ur e t es t were d ispelled . Compa red w it h
conventional pumps, the weight of the new pump has
Shaft inching test
The product overview is shown below.
been reduced by about 4 %.
3.1 Specifications
The table below shows the main specifications of a
2.2.2 Optimal design of the rotor parts
In order to reduce the sizes of the bearings, mechanical
model CB pump. Its flange meets JIS, GB, and ASME
seals, and impeller nut at the same time, the shaft
standards. Mechanical seals are used as shaft seals.
diameter has been optimized.
Figure 7 shows the comparison of the pump efficiency
As shown in Figure 5, stress analysis was carried
withη3 (evaluating value of energy conservation) between
out, simulating a state in which torque is applied to the
the representative model CNC and CB pumps. The
shaft. It was found that high stress was generated at
pump efficiency of model CB pumps has been increased
the key insertion section where the shaft diameter is
by 4 % on average, compared with model CNC pumps,
small.
and all 40 models meet η3.
For this reason, strength evaluation by an inching
3.2 Performance ranges
test shown in Figure 6 was conducted, and it was
Figures 8 and Figures 9 show performance ranges of
confirmed that there was no problem in strength.
model CB pumps.
Based on the above test results, by optimizing the
Suction diameter: 125 to 400 mm
sizes of the shaft, bearings, mechanical seals, and
Flow rate: 0.75 to 45 m3/min (50 Hz)
impeller nut, the pump weight was reduced by 3 %,
0.85 to 48 m3/min (60 Hz)
compared with conventional pumps.
They met the performance ranges of the conventional
models.
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Ebara Engineering Review No. 256 (2018-10)
Model CB Double Suction Pump for the Global Market
Specifications
90
Specification
Fluid
Fresh water, industrial water
%
88
Item
Pump efficiency
η3 (GB standard) min.
Flange rating
JIS, GB, ASME
Max. operating pressure
16 Bar
Temperature
0 to 80 ℃
Pump efficiency
Table
Frequency
50, 60 Hz
No. of poles
4P
Flow rate
48 m /min max.
Total pump head
160 m max.
Casing material
FC250, FCD450 (JIS standard)
Shaft seal
Mechanical seal
Bearing
Grease lubrication
86
84
82
80
78
76
74
72
CNC
CB
η3
3
125X80CBK
75
78.9
75.6
125X80CBJ
75
78.7
76.9
200X125CBJ
77
83
79.6
150X125CBH
77
83.6
80
300X200CBH
80
89.5
85
Comparison of pump efficiency
Fig. 7
200
400X300CBJX
100
90
80
70
60
300X150CBK 280 350X250CBJ
250
160
m
50
Total pump head
200
280
250315
400X300CBH
250 280
300X200CBJY
110 132
280 315
160
200X100CBK
90 90
350X250CBH
300X200CBJX
55
7575
315
90
250
132 160200 200
150X100CBK
280400X300CBG
300X250CBH
30
45
200 250
250X150CBJ
110
37 37 45
90
75
132
110
45
55
125X100CBK
350X250CBG
55
250
300X200CBH 110
30
160
18.522
37 200X150CBJ
22
132
55
75
200400X400CBF
125X80CBK15
30
200X125CBJ
300X250CBG
132
250X200CBH
15
90
11
18.5 22 30 30 37
45
400X350CBF
1518.5
300X200CBG
160
15
7.5
250X150CBH37
75
110
55
150X125CBJ
7.5 150X100CBJ
18.5
22
350X300CBF
18.5
11
250X200CBGY
15200X150CBH
90
5.5
30
55
250X200CBGX 300X250CBFY
11
45
5.5
37
18.5
200X125CBH
15
11
125X80CBJ 5.5
300X250CBFX
7.5
11 200X150CBG
15
22
150X125CBH150X150CBG
3.7
250X200CBF18.5
250X150CBK160
40
30
20
3.7
10
9
8
7
6
11
5.5
200X200CBF
7.5
5
4
3
0.6
1
2
3
4
5
10
Discharge rate
20
30
40
50
m3/min
Performance ranges (50 Hz)
Fig. 8
300
Total pump head
m
200
100
90
80
70
60
90
75
55
50
75
150X100CBK
250X150CBJ
90
300X250CBH
315
280
220
160
185 200185
132
90
250 350X250CBG
300X200CBH
200X150CBJ
132
200 185 220
75
90 110110
55
300X250CBG250
45 55
250X200CBH
45
22
30
220
160
18.5
132
110
200X125CBJ 55 7575
200
22
110
125X80CBK
30
15
37
55
300X200CBG
400X350CBF
45
132
30
90
150X125CBJ
185
250X150CBH 75 75
22
110
15
18.5
55
160
30 3737
18.5
11 150X100CBJ
250X200CBGY
15
200X150CBH
75
90 350X300CBF
45
37
300X250CBFY
90
15 18.5
11
7.5
18.5 22
45
250X200CBGX
200X125CBH
22
37
30
18.5
125X80CBJ
11
55
11
200X150CBG 30 300X250CBFX
5.5
150X125CBH
250X200CBF
11
7.5
22
150X150CBG 15 15
30
18.5
200X200CBF
7.5
30
40
30
20
10
9
8
7
6
5
300X150CBK
280
315
185 200 220 250
280
300X200CBJY
250
160 250X150CBK
200 220
280
250 315
132
160
250 300X200CBJX
280
350X250CBH
110
132
200 220
110200X100CBK
280
315
315
160
250
160
400X300CBG
37
45
55
45
37
125X100CBK
11
0.6
1
2
3
4
5
Discharge rate
Fig. 9
10
20
30
40
50
60
m3/min
Performance ranges (60 Hz)
─ 4 ─
Ebara Engineering Review No. 256 (2018-10)
Model CB Double Suction Pump for the Global Market
Impeller
Casing wearing ring
Casing wearing ring
Side cover
Upper casing
Side cover
Impeller nut
Unit type bearing
Shaft
Unit type bearing
Mechanical seal
Mechanical seal
Lower casing
Fig. 10
Structural drawing
3.3 Structure
4. Conclusion
Figure 10 shows the structural drawing. A model CB
pump mainly consists of upper and lower split casings,
We have provided an overview and introduced the
side covers, a double suction impeller, a shaft, unit type
features of model CB double suction pump for the
bearings, and mechanical seals.
global market.
Thanks to a casing with a through-bore structure
By employing the optimal design parameters of the
(machined from the motor side to the opposite side
impeller, discharge volute, and suction flow passage,
with the same inner diameter), bearings can be
which were obtained through DOE (design of
inserted inside the casing, resulting in a shorter
experiments) and sensitivity analyses, we have
bearing span. Furthermore, the unit type bearing that
developed pumps that meet η3, an evaluating value of
combines a bearing and a bearing cover is easy to
energy conservation in GB standards.
install and handle. Since the bearing cover has high
In the future, Ebara will improve model CB pumps by
rigidity and high strength, no abnormal load can apply
increasing the number of motor poles from two to six,
to the bearing, resulting in a longer bearing life. Also,
achieving the compatibility with high suction pressure,
since the bearing outer surface and the bearing
and so on, to promote the pumps globally from Asia,
housing inner surface make spherical contact with each
centering on the Chinese market where the production
other, the misalignment of the rotor parts is
base of the pumps is located. Energy conservation is
automatically corrected.
necessary worldwide, and we will strive to contribute to
The impeller is easy to install because it is directly
fit to the shaft and is fastened with an impeller nut.
building a sustainable society, which is a challenge
facing not only China, but also the whole world.
Since the bearing span of the shaft is shortened, the
Lastly, we would like to express our deep appreciation
shaft deflection and the clearance between the impeller
to all the people who have provided their cooperation in
and the casing wearing ring can be minimized so that
this development.
leakage loss is prevented and pump efficiency is
improved.
References
Compared to conventional model CN pumps3) for the
1)
Japanese market, the model CB pumps are compact,
2)
thanks to the through bore structure and unit type
bearings.
3)
─ 5 ─
Tatsuya MIYAMOTO: Trends in Energy Saving for Pumps
and Motors, Ebara Engineering Review, No. 236, p. 3-9 (2012-7).
Yumiko SEKINO and Hiroyoshi WATANABE: Design
Optimization of Double-Suction Pumps Based on CFD and
Experimental Validation, Turbomachinery, 44-10, p. 581-588
(2016-10).
Kiyohiko HASEYAMA: New Series of Horizontal Double
Suction Volute Pumps, Ebara Engineering Review, No. 113,
p. 39-42 (1980-7).
Ebara Engineering Review No. 256 (2018-10)