Surge Analysis
Short Description
Water Hammer report...
Description
PACKAGE 1 – UPGRADING UPGRADING OF BUKIT KEPIS AND BUKIT TAISHO TAISHO TREA TRE ATED WATER PUMPIN PUMPING G SYSTEMS
CONTENTS 1.
INTRODUCTION INTRODUCTION........................... ........................................ ........................... ............................ ............................ ........................... .......................... ......................... .................... ........1
2.
COMPUTER SIMULATION OF PUMP SYSTEMS .................. ............................... ............................ ............................ ......................... ............1
3.
ASSUMPTIONS.......................... ........................................ ........................... .......................... ........................... ............................ ............................ ......................... ....................... ............3
3.1. 3.2. 3.3.
PIPES: ............ .......................... ............................ ............................ ............................ ........................... ........................... ............................ ............................ ............................. ................. ..3 FLUID: .............. ............................ ........................... ........................... ............................ ............................ ............................ ............................ ............................ ........................... ............... 3 VESSEL: ............. ........................... ............................ ............................ ............................ ............................ ........................... .......................... ........................... ........................... .............3
4.
THEORY .......................... ........................................ ............................ ............................ ............................ ........................... ........................... ............................ ............................ ................... .....4
5.
WATER HAMMER EFFECT ON THE BUKIT TAISHO PUMPING SYSTEM ........................ 6
5.1. 5.2. 6.
WATER HAMMER EFFECT ON THE BIKIT KEPIS KEP IS PUMPING PUMPIN G SYSTEM ...................... .......... ................. ..... 10
6.1. 6.2. 7.
STEADY STATE ............ .......................... ............................. ............................ ........................... ............................ ............................ ............................. ............................. ................ 6 TRANSIENT STATE .............. ............................ ............................ ............................ ............................ ............................ ............................ ............................. ....................... ........7 STEADY STATE ............ .......................... ............................. ............................ ........................... ............................ ............................ ............................. ............................ .............10 TRANSIENT STATE .............. ............................ ............................ ........................... ........................... ............................ ............................ ............................ ...................... ........11
CONCLUSION ........................... ......................................... ........................... .......................... .......................... ........................... ........................... .......................... ....................... ..........14
List of Graphs
Appendix A - Transient Response of Bukit Taisho Pumping System Pressure envelope -with minimum initial air
A-i
Pressure envelope -with maximum initial air
A-ii
Pressure at pump end
A-iii
Flow at pump end
A-iv
Water level of the surge vessel
A-v
Air volume inside the surge vessel
A-vi
Flow through inter-connecting pipe works
A-vii
Pressure in the surge vessel
A-viii
Appendix B - Transient Response of Bukit Bu kit Kepis Pumping System Pressure envelope -with minimum initial air
B-i
Pressure envelope -with maximum initial air
B-ii
Pressure at pump end
B-iii
Flow at pump end
B-iv
Water level of the surge vessel
B-v
1. Introduction
There are two (2) pumping systems under the upgrading of Kuala Jelai water supply project, where the water hammer effect shall be studied and suitable protection systems will be proposed to control the surge pressures. The two (2) pumping systems are Bukit Kepis and Bukit Taisho pumping systems, transferring treated water to respective reservoir from a clear water tank at Kuala Jelai treatment works. After sudden shut down of the pump, flows decay rapidly at the pump discharge end. This phenomenal has caused a water column separation at the pump discharge end, which causes the pressures in the pipe to drop and creating the down surge pressures. This pressure reduction is transmitted along the pipeline at the wave velocity, and when this pressure wave is reflected, an up surge pressure is generated. The magnitude of surge pressures is related to the rate of change of flows in the pipe. The faster the change in flow rate, increasing or decreasing, the higher will be the surge pressures. Therefore it is a common practice during pumpstopping procedure, the discharge valve is first closed slowly, and then the power supply
ble, provided the limited sub-atmospheric pressure does not has any adverse effect to the systems. Nevertheless, the effects of negative pressure as listed below need to be considered seriously. a) Severe sub-atmospheric pressure will cause the pipe to collapse. b) If the sub-atmospheric pressure is minus 10m, this is the vapor pressure of water. This will cause liquid water to vaporize; the transient response of the vaporized water is difficult to predict. c) When the sub-atmospheric pressure is lower than about minus 7m, any dissolved air in water will evolve from solution. This air will not necessarily be reabsorbed into the water when pumping pressure is re-applied. The transient response of the air/water mixture is difficult to predictable accurately. d) Sub-atmospheric pressure lower than around minus 5m may cause damage to the concrete lining of the pipe if they are repeated frequently.
3. Assumptions 3.1. Pipes:
Modulus of elasticity of steel = 200 Gpa. Poisson’s ratio = .27 Conduit condition: thin wall elastic conduit. Friction factor: C= 90 (old pipes) and 120 (new pipes). 3.2. Fluid:
Fluid: Water Bulk Modulus: 2.19 Gpa Density: 1000 Kg/m 3 Operating temperature: Ambient. 3.3. Vessel:
4. Theory
Rapidly varying pressure and flow conditions in pipe systems are characterized by variation, which are both position ( x) and time (t ) dependent. These conditions are described by the dynamic equation L1
Q t
gA
H x
f
2 DA
Q | Q | 0 1
And the continuity equation
L2 a
Where
2
Q
x
gA
H t
0 2
1 a
Eq. 3 can be written as
dQ dt
gA dH
if
dx dt
and
a
a dt
f
2 DA
Q | Q | 0 4
5. Water Hammer effect on the Bukit Taisho Pumping System 5.1.
Steady State
The pumping line consists of existing 600 mm in diameter mild steel pipe, in parallel with new 800 mm in diameter mild steel pipe, 8000m long. The pipeline profile is generally flat and rise gently toward the reservoir. The surge suppression criteria will be to prevent the maximum upsurge pressures exceeding the pressure rating of the pumping system at 16 bars. Besides, the down surge pressures shall not fall below atmospheric pressure. Graph 1: System Characteristic Curve
Surge Pumping System Characteristic Curve 150.00
pressures
are
caused by the change of momentum in the pipe-
125.00
line, and momentum is 100.00
during normal flow. And the combine of new and existing surge vessels to control the surge pressures caused during maximum flow. 5.2.
Transient State
To achieve acceptable surge pressures when the pumping system is running at normal flow of 830 l/s (72mld), a 10cum surge vessel is proposed. The proposed surge vessel is proposed to be connected to the pumping main with 400mm diameter NRV. To control up surge pressures, a 200mm diameter bypass with 125 bore orifice plate is provided. A simulation of sudden shut down of the pump with the proposed vessel has show that down surge pressures of 2.7m have occurred at the pumping station. This pressure reduction is transmitted along the pipeline at the wave velocity, and when this pressure wave is reflected, an up surge pressure of 145m is experienced, also at the pumping station. The surge pressure distant plot with respect to the longitudinal profile of the pipeline is shown in Graph 2. Both the maximum up surge pressure and minimum down surge pressure are acceptable, hence the proposed 10cum surge vessel is able to control the surge pressures
low for the reduction of air inside the surge vessel due to the air that will be dissolved into the water with time, the surge vessels with maximum initial air of 5.9 cum is simulated in the computer. The maximum up surge pressure at down stream of the pump reduced to 120m, and the minimum down surge pressure has increased to 23m, with the air inside the surge vessels expanded to 16.8 m 3. To avoid the surge vessels being empty when the expanded air volume reaches 16.8 m 3, a proposed combined volume of new and existing surge vessels of 20 m 3 will be adequate. During operating condition with the pumps are running at steady speed, the water level inside the surge vessel must be set between 0.2m (HH) to 0.5m (LL) from the top of the surge vessel. If the initial water levels are not within the (HH) and (LL) limits, both the up surge and down surge pressures may drifted out side the allowable limits. Summaries of the results of the transient response of the pumping system, together with the tabulated results of the surge pressures are presented in Figure 1.
Surge Vessel Volume = 10 (Exsiting) + 10 (New) m Initial Air
Vessels
Volume m3
3
Expanded Air Maximum Surge Minimum Surge Design flow, l/s (mld) Volume m3 Pres sure m Pres sure m
Minimum Air
0.80
5.10
145.0
2.70
830 (72)
Maximum Air
2.90
9.30
136.0
17.00
830 (72)
Existing + Minimum Air Maximum Air New
1.60
9.50
150.0
4.40
1040 (90)
5.90
16.80
120.0
23.00
1040 (90)
New only
Compressor Vessel design pressure Air flow rate Pressure m 180
cum/hr
m
8.6
120
111.8
10.0
EXISTING 10m3
Pressure relief valve Blow off pressure m 180
TWL = 152.4
NEW 10m3
60 200 bypass With 125 bore orifice
600mm
Existing ,
6. Water Hammer effect on the Bikit Kepis Pumping System 6.1.
Steady State
The pumping line consists of existing 400 mm in diameter mild steel pipe, in parallel with new 500 mm in diameter mild steel pipe, 18000m long. The pipeline profile is generally flat and rise gently toward the reservoir. The surge suppression criteria will be to prevent the maximum upsurge pressures exceeding the pressure rating of the pumping system at 25 bars. Besides, the down surge pressures shall not fall below atmospheric pressure. Graph 3: System Characteristic Curve
Surge Pumping System Characteristic Curve
pressures
are
caused by the change of
250.00 225.00 200.00 175.00
momentum in the pipeline, and momentum is
caused during normal flow. And the combine of new and existing surge vessels to control the surge pressures caused during maximum flow. 6.2.
Transient State
To achieve acceptable surge pressures when the pumping system is running at normal flow of 211 l/s (18.3mld), a 2.5cum surge vessel is proposed. The proposed surge vessel is proposed to be connected to the pumping main with 200mm diameter NRV. To control up surge pressures, a 150mm diameter bypass with 100 bore orifice plate is provided. A simulation of sudden shut down of the pump with the proposed vessel has show that down surge pressures of 1.8m have occurred at chainage 17000m. This pressure reduction is transmitted along the pipeline at the wave velocity, and when this pressure wave is reflected, an up surge pressure of 200m is experienced at the pumping station. The surge pressure distant plot with respect to the longitudinal profile of the pipeline is shown in Graph 4. Both the maximum up surge pressure and minimum down surge pressure are acceptable, hence the proposed 2.5cum surge vessel is able to control the surge pressures
allow for the reduction of air inside the surge vessel due to the air that will be dissolved into the water with time, the surge vessels with maximum initial air of 3.7 cum is simulated in the computer. The maximum up surge pressure at down stream of the pump has reduced to 194m, and the minimum down surge pressure has increased to 24m, with the air inside the surge vessel expanded to 6.9 m 3. To avoid the surge vessel being empty when the expanded air volume reaches 6.9 m 3, the proposed combined volume of new and existing surge vessels of 9 m 3 will be adequate. During operating condition with the pumps are running at steady speed, the water level inside the surge vessel must be set between 0.3m (HH) to 0.65m (LL) from the top of the surge vessel. If the initial water levels are not within the (HH) and (LL) limits, both the up surge and down surge pressures may drifted out side the allowable limits. Summaries of the results of the transient response of the pumping system, together with the tabulated results of the surge pressure are presented in Figure 2.
Surge Vessel Volume = 6.5 (Exsiting) + 2.5 (New) m Initial Air
Vessels
Volume m
3
3
Expanded Air Maximum Surge Minimum Surge Design flow, l/s (mld) Volume m3 Pres sure m Pres sure m
Minimum Air
0.35
0.68
200.0
1.80
211 (18)
Maximum Air
1.03
1.92
197.0
14.00
211 (18)
Existing + Minimum Air Maximum Air New
1.30
2.70
213.0
14.50
253 (21.8)
3.70
6.90
194.0
24.00
253 (21.8)
New only
Compressor Vessel design Pressure relief valve pressure Blow off pressure Air flow rate Pressure m 260
cum/hr
m
2.4
180
45.6
10.0
EXISTING 6.5m3
m 260
TWL = 199.4
NEW 2.5m3
60 150 bypass With 100 bore orifice
200 non‐return valve
400mm Existing , + 500mm (New) 18,000m long
7. Conclusion
The proposed additional surge vessels are able to control the surge pressures occurred at the pumping systems. However, air compressors are to be provided to maintain the water levels inside the surge vessel within the upper and lower limits. When the water level in the surge vessel rises above the H level, the electrically actuated compressed air supply valve shall automatically open to supply compressed air to the surge vessel. When the water level drops below the ‘Normal’ water level the electrically actuated compressed air supply valve shall automatically close. When the water level drops below the L level, a suitable sized control valve with electric actuator shall gradually open to release the air within the vessel to allow the water level to rise. When the level rises above the ‘Normal’ water level, the control valve shall automatically close. The control of cut-in and cut-out of the compressor will be by level electrodes installed in the surge vessel. The air com pressor is sized to top up the air between the H level and N level within 30 minutes. When water levels inside the surge vessel reach either HH or LL levels, alarm should sounded and no pumps should be running, until the levels are brought back to between H
APPENDIX A
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau Kuala Jeli Water Supply Pumping to Bukit Taisho (existing vessel)
250
A -i
) m u t a D e v o b A ( . n i e r u s s e r P
200 150 100 50 0 0
1000
2000
3000
4000
5000
6000
7000
8000
Chainage in m. Files Used:
Pipeline Profile n. urge ressure Max. Surge Pressures
Max. Surge Pressure (No Protection) o ro ec on
y rau c
ra e
ne
Min. Surge Pressures
9000
P r e s s u r e e n v e l o p -w i t h m i n i u m i n i t i a l a i r
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau Kuala Jeli Water Supply Pumping to Bukit Taisho (existing vessel)
250
A -i i
) m u t a D e v o b A ( . n i e r u s s e r P
200 150 100 50 0 0
1000
2000
3000
4000
5000
6000
7000
8000
Chainage in m. Files Used:
Pipeline Profile n. urge
ressure
Max. Surge Pressures
Max. Surge Pressure (No Protection) o
ro ec on
y rau c
ra e
ne
Min. Surge Pressures
9000
P r e s s u e e n v e l o p e -w i t h m a x i u m i n i t i a l a i r
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau
P r e s s r e a t p u m p e n d
Kuala Jeli Water Supply Pumping to Bukit Taisho (existing vessel)
250
A -i i i
m , d n 200 e p m u P 150 t a d a e 100 H n o i t 50 a e l E
0
Files Used:
0
50
100
150
200 ,
.
MINIMUM AIR MAXIMUM AIR
250
300
350
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau F l o w
Kuala Jeli Water Su l Pumping to Bukit Taisho (existing vessel)
t p u m p e n
1.2
A -i v
s / m u c , d n e m u p t a w o l F
1 0.8 0.6 0.4 0.2 0 -0.2 0
50
100
150
200
- . -0.6
Files Used:
Time, Sec.
MINIMUM AIR MAXIMUM AIR
250
300
350
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau
W a t e r l e v e l o f t h e u r g e v e s s e l
Kuala Jeli Water Supply Pumping to Bukit Taisho (existing vessel)
61.6 61.4 A v
, l e61.2 v e l r e 61 t a w s 60.8 ' l e s s 60.6 e V
60.4 60.2 0 Files Used:
50
100
150
200 Time, Sec. MINIMUM AIR MAXIMUM AIR
250
300
350
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau
A i r v o l m e i n s i d e t e s u r g e v e s e l
Kuala Jeli Water Supply Pumping to Bukit Taisho (existing vessel)
18 16
A v i
m14 u c 12 , r i A10 f o m u l o V
6 4 2 0 0
Files Used:
50
100
150
200 Time, Sec. MINIMUM AIR MAXIMUM AIR
250
300
350
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau Kuala Jeli Water Supply Pumping to Bukit Taisho (existing vessel)
0.6 s
A v i i
m u c , e c i f i r o h g u o r h t w o l
0.4 0.2 0 - .
0
50
100
150
200
-0.4 -0.6 -0.8 -1
Files Used:
Time, Sec. MINIMUM AIR MAXIMUM AIR
250
300
350
F l o w t r o u g h i n t e r c o n n e c t i n g p i p e w o r k s
C:\Jobs\Munseh\Re ort\Taisho\ Results-Vessel-Taisho.xls . Sheet2
Program by A.L. Lau
P r e s s u r e i n s i d e s u r g e v e s s e l
Kuala Jeli Water Supply Pumping to Buk it Taisho (exist ing vessel) 160
A v i i i
m ,140 l e s s e V n 100 i e r u 80 s s e P e g 40 u a G20
0 Files Used:
50
100
150
200 Time, Sec.
MINIMUM AIR MAXIMUM AIR
250
300
350
APPENDIX B
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2
Program by A.L. Lau Kuala Jelai Water Suppl y .
300
B i
) m t a D e v o b A ( . n i e r u s s e r P
250 200 150 100 50 0 0
2000
4000
6000
8000
10000
12000
14000
16000
18000
Chainage in m . Files Used:
Pipeline Profile
Max. Surge Pressure (No Protection)
Min. Surge Pressure (No Protection)
Hydraulic Grade Line
Max. Surge Pressures
Min. Surge Pressures
20000
P r e s u r e e n v e l o p e -w i t h m i n i u m i n i t i a l a i r
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2 .
Program by A.L. Lau
P r e s s u r e n v e l o p e i t h m a x i m u
Kuala Jelai Water Supply Pumping t o Kepis Reservoir (Max. Flow)
300 ) m u t a
B i i
e v o b A ( . m n i e r u s s e r P
250
150 100
0 0
2000
4000
6000
8000
10000
12000
14000
16000
18000
Chainage in m. Files Used:
Pipeline Profile
Max. Surge Pressure (No Protection)
Min. Surge Pressure (No Protection)
Hydraulic Grade Line
Max. Surge Pressures
Min. Surge Pressures
20000
i n i t i a l a i r
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2 .
Program by A.L. Lau
P r e s s u r e a t p u m p e d
Kuala Jelai Water Su l Pumping t o Kepis Reservoir (Max. Flow)
300 m , d 250 n
B i i i
p m200 u P t a 150 d a H 100 n o i t a 50 v e l E
Files Used:
0
100
200
300 Time, Sec. MINIMUM AIR MAXIMUM AIR
400
500
600
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2 .
Program by A.L. Lau
Kuala Jelai Water Suppl y ump ng o ep s eservo r ax.
F l o w a p u m p e n d
ow
0.3
B i v
s 0.25 / m 0.2 u c , 0.15 d n e 0.1 p m 0.05 u p t a -0.05 w o -0.1 l F
0
100
200
300
-0.15 - .
Files Used:
Time, Sec.
MINIMUM AIR MAXIMUM AIR
400
500
600
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2 .
Program by A.L. Lau
W a t e r l v e l o f t h e s u r g e v e s s e l
Kuala Jelai Water Suppl y Pumping t o Kepis Reservoir (Max. Flow)
61.3 61.2
B v
m61.1 , l e v 61 e l r 60.9 e t a w60.8 s ' l 60.7 s s 60.6 e V
60.5 60.4 60.3
0 Files Used:
100
200
300 Time, Sec. MINIMUM AIR
400
500
600
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2 .
Program by A.L. Lau
A i r v o l u
Kuala Jelai Water Suppl y Pumping to Kepis Reservoir (Max. Flow)
e i n s i d e t h e s u r g e v e s s e l
8 7
B v i
m u c , r i A f o e m u l o V
5 4 3 2 1 0 0
Files Used:
100
200
300 Time, Sec. MINIMUM AIR MAXIMUM AIR
400
500
600
C:\Jobs\Munseh\Report\Kepis\[Results-Vessel-Kepis.xls]Sheet2 .
Program by A.L. Lau Kuala Jelai Water Supply Pumping t o Kepis Reservoir (Max. Flow)
0.2 0.15
B v i i
s / m . u c , e 0.05 c i f i r 0 o h g -0.05 o r h t
0
100
200
300
-0.1
w o -0.15 l F
-0.2 -0.25 Files Used:
Time, Sec. MINIMUM AIR
400
500
600
F l o w t h o u g h i n t e r c n n e c t i n g p i e w o r k s
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