FACULTY OF CIVIL AND ENVIRONMENTAL
ENGINEERING
DEPARTMENT OF WATER & ENVIROMENTAL ENGINEERING
WATER ENGINEERING LABORATORY
LAB REPORT Subject Code BFC 21201
Code & Experiment Title MKA – 04 ; SERIES AND PARALLEL PUMP TEST
Course Code 2 BFF/1
Date 5 DECEMBER 2011
Section / Group 5/2
Name MUHAMMAD IKHWAN BIN ZAINUDDIN (DF100018)
Members of Group 1. AFANDI BIN ABD WAHID (DF100122)
2.MOHD HASIF BIN AZMAN (DF100079)
3.MUHAMMAD HUZAIR BIN ZULKIFLI (DF100040)
Lecturer/Instructor/Tutor CIK AMNANI BIN ABU BAKAR
EN JAMILULLAIL BIN AHMAD TAIB
Received Date 12 DECEMBER 2011
Comment by examiner
Received
STUDENTS’ ETHICAL CODE
(SEC)
DEPARTMENT OF WATER & ENVIRONMENTAL
ENGINEERING
FACULTY OF CIVIL & ENVIRONMENTAL
ENGINEERING
UNIVERSITI TUN HUSSEIN ONN MALAYSIA
BATU PAHAT, JOHOR
“I declare that I have prepared this report with my own efforts. I also
declare not receive or give any assistance in preparing this report and
make this affirmation in the belief that nothing is in, it is true”
……………………………………….
(STUDENT SIGNATURE)
NAME : MUHAMMAD IKHWAN BIN ZAINUDDIN
MATRIC NO. : DF100018
DATE : 11 DECEMBER 2011
STUDENTS’ ETHICAL CODE
(SEC)
DEPARTMENT OF WATER & ENVIRONMENTAL
ENGINEERING
FACULTY OF CIVIL & ENVIRONMENTAL
ENGINEERING
UNIVERSITI TUN HUSSEIN ONN MALAYSIA
BATU PAHAT, JOHOR
“I declare that I have prepared this report with my own efforts. I also
declare not receive or give any assistance in preparing this report and
make this affirmation in the belief that nothing is in, it is true”
……………………………………….
(STUDENT SIGNATURE)
NAME : AFANDI BIN ABD WAHID
MATRIC NO. : DF100122
DATE : 11 DECEMBER 2011
STUDENTS’ ETHICAL CODE
(SEC)
DEPARTMENT OF WATER & ENVIRONMENTAL
ENGINEERING
FACULTY OF CIVIL & ENVIRONMENTAL
ENGINEERING
UNIVERSITI TUN HUSSEIN ONN MALAYSIA
BATU PAHAT, JOHOR
“I declare that I have prepared this report with my own efforts. I also
declare not receive or give any assistance in preparing this report and
make this affirmation in the belief that nothing is in, it is true”
……………………………………….
(STUDENT SIGNATURE)
NAME : MOHD HASIF BIN AZMAN
MATRIC NO. : DF100079
DATE : 11 DECEMBER 2011
STUDENTS’ ETHICAL CODE
(SEC)
DEPARTMENT OF WATER & ENVIRONMENTAL
ENGINEERING
FACULTY OF CIVIL & ENVIRONMENTAL
ENGINEERING
UNIVERSITI TUN HUSSEIN ONN MALAYSIA
BATU PAHAT, JOHOR
“I declare that I have prepared this report with my own efforts. I also
declare not receive or give any assistance in preparing this report and
make this affirmation in the belief that nothing is in, it is true”
……………………………………….
(STUDENT SIGNATURE)
NAME : MUHAMMAD HUZAIR BIN ZULKIFLI
MATRIC NO. : DF100040
DATE : 11 DECEMBER 2011
1.0 INTRODUCTION
Pumps can be arranged in serial or parallel to provide additional
head or flow rate capacity.
i) Pumps in Serial - Heads Added
When two (or more) pumps are arranged in serial, their resulting pump
performance curve is obtained by adding their heads at same flow rate as indicated
in the figure below.
Figure 1 - Pumps in Serial - Heads Added
Centrifugal pump in series are used to overcome larger system head loss
than one pump can handle alone. For two identical pumps in series the head will
be twice the head of a single pump at the same flow rate. With constant flowrates
the combined head moves from 1 to 2. In practice the combined head and flow
rated moved along the system curve to 3. If one of the pumps stops, the operation
point moves along the system resistance curve from point 1 to point 2 - head and
flow rate are decreased. Series operation of single stage pumps is seldom
encountered - more often multistage centrifugal pumps are used.
ii) Pumps in Parallel - Flow Rate Added
When two or more pumps are arranged in parallel their resulting
performance curve is obtained by adding their flowrates at the same head as
indicated in the figure below.
Figure 2 - Pumps in Parallel - Flow Rate Added
Centrifugal pumps in parallel are used to overcome larger volume flows
than one pump can handle alone. For two identical pumps in parallel the flowrate
will double (moving from 1 to 2) compared to a single pump if head is kept
constant. In practice the combined head and volume flow moves along the system
curve as indicated from 1 to 3. If one of the pumps in parallel or series stops, the
operation point moves along the system resistance curve from point 3 to point 1 -
the head and flow rate are decreased.
2.0 OBJECTIVE
To evaluate the pump characteristics and performance of single two pumps in series and
two pumps in parallel at a fixed speed.
3.0 LEARNING OUTCOMES
At the end of the course, students should be able to apply the knowledge and skills they
have learned to:
a. Understand the concept of pump operations
b. Understand the pump performances
c. Understand the factors which influence the performance of the pump
4.0 THEORY
1. Atmospheric pressure or barometer pressure can be indicated by the absolute pressure
minus gauge pressure, Pb = 1013 – 0.1055EL where EL is the elevation above mean
seas level at the point to be measured.
2. Pressure head, Hp = P/ (m) where P is the pressure (N/m2) and is the specific
weight (kg/m3).
3. Velocity Head, Hv = V2/2g (m) where V is liquid velocity.
4. Static Head, Hs. Height of liquid column above pump centerline on the discharge side
of the pump is called Static Discharge Head. Head of liquid column above pump
centerline on the pump suction side is called Static Suction Head. If the liquid level on
the pump suction side is lower than pump centerline, then height is called Static
Suction Lift. Total Static Head is the algebraic difference between Static Discharge
Head and Static Suction Head.
5. Friction Head, (Hf) is the small head loss due to friction between liquid and passage
wall (from the suction side of the pump to the discharge side). The value of loses
depend on the flow. The higher the flow rate, the higher is the friction loss.
6. Total Head of Fluid (HT) is the total head at any point of the liquid is the sum of all
heads at that particular point, HT = Hp + Hv + HS or HT = P/ + V2/2g + z.
7. Power is the amount of work done per unit time. Power output of pump, Wo = 1.635QP
(watts) where Q is flow rate (lt/min) and P is pressure (kg/cm2). Power input to the
pump, Wi =1.0277Frn (watts) where F is the dynamometer turning force (watt), r is
the dynamometer arm length (m) and n is the prime mover speed (RPM); or Wi =
0.10476Tn (watt) where torque, T = Fr (Nm).
8. Pump efficiency, p = W0/W1 where Wo is the power that pump delivers to liquid and
W1 is the input power.
4.1 Centrifugal Pump
The principle theory of the centrifugal pump is as follows:
1. Flow rate is directly proportional to the impeller speed and to the third
power of the impeller diameter.
2. Total head is directly proportional to the square power of the impeller
diameter.
3. Power is directly proportional to the third power of the impeller speed and
to the fifth power of the impeller diameter.
4. All the interaction occurs within the pump volute housing creating the
Total Dynnamic Head (HTDH). The direction of pump discharge flow is at
90 degree angle to the pump suction flow.
5. 2
1
Q
Q=
3
22
3
11
Dn
Dn;
2
1
H
H=
2
2
2
1
2
1
2
1
Dn
Dn;
2
1
p
p=
5
2
3
2
5
1
2
1
Dn
Dn where D is impeller diameter, Q
is flow rate, p is shaft brake horsepower, n is impeller speed, H is total
dynamic head, 1 is pump no. 1 and 2 is pump no.2.
6. Typical performance characteristic of centrifugal pump are shown.
4.2 Operational Of Pumps Connected In Series And Parallel
Each individual pump has different operating performances characteristics
1. Series Operation
In case of two pumps connected for a series operation, the flow rates of
pump no. 1 and pump no. 2 will be equal; and the combined Total Head of
2 pump will be equal to the sum of the Total Heads of pump no.1 and no.
2: QT = Q1 + Q2 , Htotal = HT1 + HT2. However in actual practice, the
combination Total Head will be slightly lower that HT1 + HT2 due to the
additional loss of power in the system as shown in figure (a).
2. Parallel Operation
In case of two pumps connected of parallel operation, the pump suction and
discharge pressure head will be equal and the combined Total Flow Rate of
the system will be the sum of the Flow Rate of Pump no. 1 and pump no. 2,
Htotal = HT1 + HT2 and QT = Q1 + Q2 as shown in figure (b).
Figure 3 – Series Operation (a) and Parallel Operation (b)
5.0 EQUIPMENTS
This is a self contained bench top unit consisting of two independent sets of centrifugal
pump. By manipulating flow control valves, each pump can be operated individually or
both pumps connected in series or parallel for measurement of flow rate, head at three
different speeds.
Figure 4 – Series and Parallel Pump Equipment
Figure 5 – Stopwatch
Main Power
Pump
Water
Meter
Suction Gauge
Discharge
Gauge
Valve
6.0 PROCEDURES
1. Hydraulics Bench storage tank fill water up to a nearly full level
(5-10cm from the top).
2. Make sure that all pressure gauges both in the suction and discharge sides should read
“0”. If not, disconnect pressure tube (white plastic tube) at either side to release the
pressure and then reconnect it.
3. The schematic piping system of the test set show on a figure below.
4. Turn off both pumps and close the main power of the control board respectively after
completion of the test.
5. Record the values of series and parallel.
Figure 6 – Schematic Piping System
6.1 Performance Test of Pump No. 1
1. Close valves V2, V3, and open valves V1, V4 and V5
2. Turn on pump no. 1 and set the speed at high speed
3. Record the following data:
i. Suction Pressure =………………kg/cm2
ii. Discharge Pressure =……………kg/cm2
iii. Flow Volume =…………………...liter
iv. Time Period =…………………….sec.
4. Slightly close the discharge valve (V5) to further increase the outlet pressure
at an increment of 0.1kg/cm2 and repeat 3
5. Repeat 4 until discharge valved is closed
6. Repeat 2 to 5 for medium and low speed levels.
6.2 Performance Test of Pump No. 2
1. Close valves V1, V3, V4, and open valves V2 and V5
2. Turn on pump no. 2 and set the speed at high speed level
3. Record the same data as in 5.1(3)
4. Slightly close the discharge valve (V5) to further increase the outlet pressure
at an increment of 0.1kg/cm2 and repeat 3
5. Repeat 4 until discharge valved is closed
6. Repeat 2 to 5 for medium and low speed levels.
6.3 Performance of Pump No. 1 and Pump No. 2 in Series Connection
1. Close valves V2, V4 and open valves V1, V3 and V5
2. Turn on both pumps and set the speed at high speed level
3. Record the following data:
i. Suction Pressure, P1 =……...……..kg/cm2
ii. Discharge Pressure, P3 =……….....kg/cm2
iii. Flow Volume =……………………... liter
iv. Time Period =………………………..sec.
4. Slightly close the discharge valve (V5) to further increase the outlet pressure
at an increment of 0.1kg/cm2 and repeat 3
5. Repeat 4 until discharge valved is closed
6. Repeat 2 to 5 for medium and low speed levels.
6.4 Performance of Pump No. 1 and Pump No. 2 In Parallel Connection
1. Close valves V3 and open valves V1, V2, V4 and V5
2. Turn on both pumps and set the speed at high speed level
3. Record the following data:
i. Suction Pressure, P1 and P2 =…….....kg/cm2
ii. Discharge Pressure, P3 =………...…...kg/cm2
iii. Flow Volume =…………………...……..liter
iv. Time Period =……………………...…….sec.
4. Slightly close the discharge valve (V5) to further increase the outlet pressure
at an increment of 0.1kg/cm2 and repeat 3
5. Repeat 4 until discharge valved is closed
6. Repeat 2 to 5 for medium and low speed levels.
7.0 RESULT
a) Pump No.1
SPEED 2 SPEED 3
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
0.15 0.08 21.28” 84.568 0.007 0.069 0.08 0.30 24.36” 73.89 0.022 0.216
0.25 0.08 25.31” 71.118 0.017 0.167 0.16 0.30 29.44” 61.14 0.006 0.137
0.35 0.08 32.91” 54.695 0.027 0.265 0.26 0.28 39.28” 45.28 0.002 0.020
0.45 0.08 49.31” 36.504 0.037 0.363 0.34 0.28 86.06” 20.92 0.006 0.059
0.54 0.08 70.13” 25.667 0.046 0.451 0.42 0.28 141.04” 12.76 0.014 0.137
b) Pump No.2
SPEED 2 SPEED 3
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
0.26 0.22 64.19” 28.042 0.004 0.039 0.12 0.34 28.44” 63.29 0.022 0.216
0.27 0.22 64.19” 28.042 0.005 0.049 0.16 0.34 30.37” 59.27 0.018 0.177
0.28 0.22 99.71” 18.052 0.006 0.059 0.22 0.32 33.78” 53.29 0.010 0.098
0.29 0.22 99.71” 18.052 0.007 0.069 0.26 0.32 37.22” 48.36 0.006 0.059
0.30 0.22 179.29” 10.040 0.008 0.078 0.30 0.32 40.00” 45.00 0.002 0.020
c) Pump No. 1 and No.2 in Series Operation
SPEED 2 SPEED 3
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
0.04 0.32 24.44” 73.65 0.028 0.275 0.10 0.42 16.90” 106.51 0.032 0.314
0.31 0.26 31.31” 57.49 0.005 0.049 0.34 0.38 22.09” 81.48 0.004 0.034
0.57 0.26 40.60” 44.33 0.031 0.304 0.58 0.38 29.34” 61.35 0.020 0.196
0.84 0.26 55.78” 32.27 0.058 0.569 0.82 0.34 43.66” 41.23 0.048 0.471
1.10 0.26 66.09” 27.24 0.084 0.824 1.06 0.34 124.68” 14.44 0.072 0.706
d) Pump No. 1 and No.2 in Parallel Operation
SPEED 2 SPEED 3
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
PDIS
(kg/cm2)
PSUC
(kg/cm2)
Time
(s/30ltr)
Flowrate,
Q (ltr/min)
PTOTAL
(kg/m2)
PHEAD
(kg/m2)
0.04 0.49 22.78” 79.02 0.045 0.441 0.04 0.53 18.87” 95.39 0.049 0.481
0.19 0.49 36.32” 49.56 0.030 0.294 0.16 0.52 23.65” 76.11 0.036 0.353
0.33 0.49 57.94” 31.07 0.016 0.157 0.30 0.52 26.50” 67.92 0.022 0.216
0.48 0.49 88.78” 20.27 0.001 0.010 0.42 0.51 35.03” 51.38 0.009 0.088
0.62 0.49 190.41” 9.45 0.013 0.128 0.54 0.50 56.22” 32.12 0.004 0.039
8.0 ANALYSIS DATA
Calculation for Flowrate,Q (Ltr/min), PTOTAL (kg/m2) and PHEAD (kg/m
2)
a) Calculation for Speed 3, Pump No.1
PDIS Flowrate,Q (ltr/min) = 30 lt x 60s
time,s 1 min
PTOTAL (kg/m2) = (PDIS – PSUC) x 1000
1002
PHEAD (kg/m2) = (PTOTAL x 9.81)
0.08 = 30 lt x 60s
24.36s 1 min
= 73.89 lt/min
= (0.08 – 0.30) x 1000
1002
= 0.022 kg/m2
= 0.022 x 9.81
= 0.216 kg/m2
0.16 = 30 lt x 60s
29.44s 1 min
= 61.14 lt/min
= (0.16 – 0.30) x 1000
1002
= 0.014 kg/m2
= 0.014 x 9.81
= 0.137 kg/m2
0.26 = 30 lt x 60s
39.28s 1 min
= 45.28 lt/min
= (0.26 – 0.28) x 1000
1002
= 0.002 kg/m2
= 0.002 x 9.81
= 0.020 kg/m2
0.34 = 30 lt x 60s
86.06s 1 min
= 20.92 lt/min
= (0.34 – 0.28) x 1000
1002
= 0.006 kg/m2
= 0.006 x 9.81
= 0.059 kg/m2
0.42 = 30 lt x 60s
141.04s 1 min
= 12.76 lt/min
= (0.42 – 0.28) x 1000
1002
= 0.014 kg/m2
= 0.014 x 9.81
= 0.137 kg/m2
b) Calculation for Speed 3, Pump No.2
PDIS Flowrate,Q (ltr/min) = 30 lt x 60s
time,s 1 min
PTOTAL (kg/m2) = (PDIS – PSUC) x 1000
1002
PHEAD (kg/m2) = (PTOTAL x 9.81)
0.08 = 30 lt x 60s
28.44s 1 min
= 63.29 lt/min
= (0.12 – 0.34) x 1000
1002
= 0.022 kg/m2
= 0.022 x 9.81
= 0.216 kg/m2
0.16 = 30 lt x 60s
30.37s 1 min
= 59.27 lt/min
= (0.16 – 0.34) x 1000
1002
= 0.018 kg/m2
= 0.018 x 9.81
= 0.177 kg/m2
0.26 = 30 lt x 60s
33.78s 1 min
= 53.29 lt/min
= (0.22 – 0.32) x 1000
1002
= 0.010 kg/m2
= 0.010 x 9.81
= 0.098 kg/m2
0.34 = 30 lt x 60s
37.22s 1 min
= 48.36 lt/min
= (0.26 – 0.32) x 1000
1002
= 0.006 kg/m2
= 0.006 x 9.81
= 0.059 kg/m2
0.42 = 30 lt x 60s
40.00s 1 min
= 45.00 lt/min
= (0.30 – 0.32) x 1000
1002
= 0.002 kg/m2
= 0.002 x 9.81
= 0.020 kg/m2
c) Calculation for Series Operation, Pump No.1 and No.2
PDIS Flowrate,Q (ltr/min) = 30 lt x 60s
time,s 1 min
PTOTAL (kg/m2) = (PDIS – PSUC) x 1000
1002
PHEAD (kg/m2) = (PTOTAL x 9.81)
0.08 = 30 lt x 60s
16.90s 1 min
= 106.51 lt/min
= (0.10 – 0.42) x 1000
1002
= 0.032 kg/m2
= -0.032 x 9.81
= 0.314 kg/m2
0.16 = 30 lt x 60s
22.09s 1 min
= 81.48 lt/min
= (0.34 – 0.38) x 1000
1002
= 0.004 kg/m2
= 0.004 x 9.81
= 0.039 kg/m2
0.26 = 30 lt x 60s
29.34s 1 min
= 61.35 lt/min
= (0.58 – 0.38) x 1000
1002
= 0.020 kg/m2
= 0.020 x 9.81
= 0.196 kg/m2
0.34 = 30 lt x 60s
43.66s 1 min
= 41.23 lt/min
= (0.82 – 0.34) x 1000
1002
= 0.048 kg/m2
= 0.048 x 9.81
= 0.471 kg/m2
0.42 = 30 lt x 60s
124.68s 1 min
= 14.44 lt/min
= (1.06 – 0.34) x 1000
1002
= 0.072 kg/m2
= 0.072 x 9.81
= 0.706 kg/m2
d) Calculation for Parallel Operation, Pump No.1 and No.2
PDIS Flowrate,Q (ltr/min) = 30 lt x 60s
time,s 1 min
PTOTAL (kg/m2) = (PDIS – PSUC) x 1000
1002
PHEAD (kg/m2) = (PTOTAL x 9.81)
0.08 = 30 lt x 60s
18.87s 1 min
= 95.39 lt/min
= (0.04 – 0.53) x 1000
1002
= 0.049 kg/m2
= 0.049 x 9.81
= 0.481 kg/m2
0.16 = 30 lt x 60s
23.65s 1 min
= 76.11 lt/min
= (0.16 – 0.52) x 1000
1002
= 0.036 kg/m2
= 0.036 x 9.81
= 0.353 kg/m2
0.26 = 30 lt x 60s
26.50s 1 min
= 67.92 lt/min
= (0.30 – 0.52) x 1000
1002
= 0.022 kg/m2
= 0.022 x 9.81
= 0.216 kg/m2
0.34 = 30 lt x 60s
35.03s 1 min
= 51.38 lt/min
= (0.42 – 0.51) x 1000
1002
= 0.009 kg/m2
= 0.009 x 9.81
= 0.088 kg/m2
0.42 = 30 lt x 60s
56.22s 1 min
= 32.12 lt/min
= (0.54 – 0.50) x 1000
1002
= 0.004 kg/m2
= 0.004 x 9.81
= 0.039 kg/m2
9.0 QUESTIONS
1. For pump no.1 and no.2 :
Plot curve showing flowrate on the Y-axis versus pressure (occasionally expressed in
metres of head) on the X-axis for a constant pump speed by drawing smooth curve
through points obtained from the calculations.
Graph flowrate versus pressure (speed 2)
Based on the graph, we show that the pressures are decrease when the flowrate are
increase. Compare between pump no. 1 and pump no. 2, the curve of pump 1 are
higher than pump 2.
Graph flowrate versus pressure (speed 3)
Based on the graph, the speed 3 is faster than speed 2, so, it has more flowrate with
less value of pressure head. Compare between pump no. 1 and pump no. 2, the curve
of pump 1 are higher than pump 2.
2. For both two pumps in series and parallel operation :
In this case of series and parallel operation, please compare the additional pressure and
flowrate according to the theory.
Graph flowrate versus pressure-series and parallel (speed 2)
From the graph, we show that have different curve between series and parallel
operation. The curve of parallel operation is higher than the curve of series
operation. The value flowrate of parallel are more than flowrate of series
operation.
Graph flowrate versus pressure-series and parallel (speed 3)
From the graph, there is also difference in curve between series and parallel
operation. The curve of parallel operation is lower than the curve of series
operation. The value flowrate of parallel are less than flowrate of series operation.
10.0 DISCUSSION
A pump is a device used to move liquids, or slurries. A pump moves liquids from
lower pressure to higher pressure, and overcomes this difference in pressure by adding
energy to the system (such as a water system). A gas pump is generally called a
compressor, except in very low pressure-rise applications, such as in heating, ventilating,
and air-conditioning, the equipment is known as fans or blowers.
Based on the result from the table, the increment of flow rate was influence to the
decreasing of pressure head of suction that give a negative sign. These two data was
influence to the pressure in discharge section which is controlled. So,
i. Manipulated variable shows by the pressure in discharge and speed of pump.
ii. Dependent variable shows by the pressure in suction and flow rate.
iii. Constant variable shows by the volume of water in the tank.
Discharge Cavitations
Discharge Cavitations occurs when the pump discharge is extremely high. It
normally occurs in a pump that is running at less than 10% of its best efficiency point.
The high discharge pressure causes the majority of the fluid to circulate inside the pump
instead of being allowed to flow out the discharge. As the liquid flows around the impeller
it must pass through the small clearance between the impeller and the pump cutwater at
extremely high velocity. This velocity causes a vacuum to develop at the cutwater similar
to what occurs in a venture and turns the liquid into a vapor. A pump that has been
operating under these conditions shows premature wear of the impeller vane tips and the
pump cutwater.
Suction Cavitations
Suction Cavitations occurs when the pump suction is under a low pressure/high
vacuum condition where the liquid turns into a vapor at the eye of the pump impeller.
This vapor is carried over to the discharge side of the pump where it no longer sees
vacuum and is compressed back into a liquid by the discharge pressure. This imploding
action occurs violently and attacks the face of the impeller. An impeller that has been
operating under a suction cavitations condition has large chunks of material removed from
its face causing premature failure of the pump.
Figure 7 – High Discharge Pressure Figure 8 – Low Pressure
From the table and graph, overall we can say that flow rate increase when the
pressure head in suction decrease to negative value. This sign shows that there are
vacuum conditions at the point after we placed the pump that allowing water to suck in
that point to make the water move in the pipe. This sign also tell that the point is in low
pressure than other point in the tank and before we placed the pump. So, the higher
pressure will be suck to the lower pressure because it is a concept of pressure.
This experiment didn’t give an exact value cause by some errors in the system and
other factors, such as:
Parallax error.
It happens while taking a reading using gauge meter and stop watch where the
reader didn’t use a proper way to get a right reading.
To prevent this problem, the reader should learn and practise by understand the
procedure to get reading otherwise get some help. Other than that, the reader
should have sharp eye because meter gauge don’t give a small scale to use. He or
she must estimate the value correctly or nearly for right value that can be used.
Systematic error.
This error cause by apparatus that are not perfect and have some problem such as
leaking or a big losses energy cause by friction in the pipe.
To prevent this error, the apparatus should be test before the experiment begins.
Random error.
There are many data that was taken and sometimes the data didn’t give a good
results cause by randomly results.
To reduce this, reader should take more than one reading and take the average.
Additionally, a person who takes the reading should not be changed.
11.0 CONCLUSION
According to the experiments, can evaluate the pump characteristics and
performances of single two pumps in series and two pumps in parallel at a fixed speed.
Pumps are used to convert mechanical energy into fluid energy and allow liquids to be
moved from one place to another. From this experiment, can understand fully the types of
pumps available and their different characteristics. Measurements of head, flow, speed
and torque allow the performance of each pump to be determined and compared.
Therefore, the experiments assumed success.
12.0 REFERENCES
Roberson, J.A, Cassidy, J.J & Chaudry, M.H. (1998) ‘Hydraulic Engineering’, Wiley.
Ab Aziz Abdul Latiff, Hidraulik, Jabatan Kejuruteraan Awam Dan Alam Sekitar,
Penerbit UTHM.
White Frank M.(1979). Fluid Mechanics. Mc Graw, Hill.University of Rhode Island.
United States of America, pg 636 - 642.
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