Case Study-Al Bab-Tadef PS Perfromance Feasibilty

7/27/2019 Case Study-Al Bab-Tadef PS Perfromance Feasibilty

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AL BAB TADEF IRRIGATION PROJECT Technical evaluation and Feasibility studyof Pumping stations performance

AL BAB TADEF IRRIGATION PROJECT

Technical evaluation and Feasibility study of

Pumping stations performance

Study prepared by

Ghassan Al Salem

28/5/2011


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Page 2 of 24 CASE STUDY-AL BAB-TADEF PS PERFROMANCE FEASIBILTY.DOCX

INDEX

1. General 3

2. Description of the pumping plant 3

2.1. Design Data 3

3. Plant Operation evolution 4

3.1. Historical sequence of problems 4

3.2. Operation parameters 4

3.3. Causes of Problems: 5

4. Technical measures taken by the administration and its suitability 7

4.1. Operating the plant in manual regime 7

4.2. Casting pump foundation with concrete: 7

4.3. Erecting a concrete slab extending over the suction openings (Beginning of 2009) 7

4.4. Installation of air release valves at pump casing crown 7

4.5. Repair of impellers 7

4.6. Installation of weed screen at PS1 Inlet 8

4.7. Installation of control system 8

5. Extra implementation Costs in plants at actual operation regime 8

5.1. Losses due to reduced efficiency after repair 8

5.2. Losses caused by Partial valve closure 10

6. Other technical remarks 12

6.1. Discharge valves 12

6.2. non return valve 13

6.3. Pump packing 13

7. technical Recommendations and proposals for improving performance 13

7.1. immediate maintenace measures 13

7.2. Measures during maintenance period 14

7.3. Measures required for reducing energy loss 14

8. Conclusions 23


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TECHNICAL AND ECONOMICAL EVALUATION

For the performance of the Pumping stations

At Al Bab-Tadef Irrigation development project

1. GENERALThe purpose of this report is the evaluation of the technical performance, feasibility of pumping

process, determining the causes of problems occurred during start up and recommending

optimum operation method

Project Owner: Ministry of Irrigation, General Establishment for Land Development Function of the pumping plant: elevating water from Maskaneh west irrigation

Channel to a number of elevated and ground tanks to provide for the irrigation of

6700 ha in Al Bab Tadef area

This study is based on the measurements made at the first and second pumpingstation and the results are generalized to the third PS

2. DESCRIPTION OF THE PUMPING PLANTAccording to adopted design, the water is pumped using 3 pumping stations on different levels

according to levels of irrigated areas using main pumps for providing the main flowrate and

secondary pumps to supply partial demand required at each pumping level and according to

served area.

The pumps used are of the double suction type2.1. DESIGN DATADescription Unit PS1 PS2 PS3

Group 1 Group 2Area served by the plant Ha 6700 5945 3061Design flow m3/s 5.17 3.8 0.71 2.31Total Static head< mWC 61.83 62.76 45.6 45.43Number of main pumps (Op-Std.by) No 4(3+1) 3(2+1) 3(2+1) 4(3+1)Number of secondary pumps No 2 2 I 2Main pump design flow m3/s 1.25-1.4 1.23-1.35 0.22-0.30 0.5-0.65Secondary pump design flow m3/s 0.62-0.7 0.61-0.7 I 0.25-0.32NPSHR at pump design flow mWC 8 8 8 8Min. Suction level mASL 366.19 419.24 419.24 471.57Max suction level mASL 367.17 421.24 421.24 473.57Min Discharge level mASL 425.6 479.7 Direct 515.00Max Discharge level mASL 428.02 482.00 Direct 517.00Pressure line length m 3509 3258 Direct 512.00Pressure line size mm 1x1400 1x1200 1x800 1x1000Table 1


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3. PLANT OPERATION EVOLUTION3.1. HISTORICAL SEQUENCE OF PROBLEMSThe plant started operation by the local staff on 18/03/2007; the start up was accompanied by agroup of problems summarized as follows:

Vortices in PS1 suction basins entrained Air in pumped water Vibration in Pumps One of pumps packing does not pass cooling water One of the non-return valves has a defected piston Cavitation and wear in pumps impellers (Figure 1- Cavitation in pump impeller)

Figure 1- Cavitation in pump impeller

Those phenomena have a very bad effect on pump performance as they cause wear in moving

and fixed parts of the pump and reduce the plant efficiency in general due to the reduction in

pumped water quantity against same consumed power

Those problems or part thereof continued during the years 2008-2009 when the administration

has applied some solutions to the problems, this shall be discussed in the following clause 5 in

detail

3.2. OPERATION PARAMETERSThe following operation parameters were collected during the site visit on 8/04/2011, in

addition to some measurement which were carried out by the administration during thepreparation of this study; According to this data we indicate the following

3.2.1. OPERATION POINTS AT SITE VISIT DATEDepth

cm W.LMASL CurrentA PowerkW Flowm3/hr PressurebarPS1, 3 Pumps operating

Pump1 293 366.25 117 1170 4200 8.2Pump2 293 366.25 117 1170 4200 8.2Pump3 293 366.25 117 1170 4200 8.2PS2, 2 main Pumps +1 sec.Main pump 250 419.48 122 1220 4350 8.4Secondary Pump 250 419.48 68 684 2300 8.4Table 2


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3.2.2. OPERATION POINTS BEFORE AND AFTER REPAIRSPumps operated at the points shown in the following table before and after the repairs

W. Depth Current Power Flow PressurePS2 cm A kW m3/hr barMain Pump before repair 250 N.A 1240 4300 8.4Main Pump after repair 250 N.A. 1200 4400 8.4Table 3

3.2.3. PRESSURE UP AND DOWNSTREAM THE PUMPSThe Administration has provided us, thankfully, the pressure readings upstream and

downstream the control valves according to number of operating pumps, this is shown in the

following tableNo of operating pumps 1 2 3 4PS1 Pressure Upstream valve (bars) 8.17

Pressure downstream valve (bars) 5.9 6.18 6.7 7.29PS2 Pressure Upstream valve (bars) 8.4

Pressure downstream valve (bars) 6.0 6.8 8.0Table 4

3.2.4. IRRIGATION PROGRAMMonth Mar Apr May June July Aug Sep Oct

Pumped volume 1000m3 1,906 7,652.3 6,469.1 4,755.6 8,176 8,483 6,464 2,520Table 5

3.3. CAUSES OF PROBLEMS:3.3.1. VORTICES AND ENTRAINED AIRThe design did not take into consideration the critical submersion depth (hc)


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This value is not available according to suction conditions in the station, and which is calculated

as shown in the following Table 8

Description Symb Unit PS1 Reference

Data InputNo of Operating Pumps n 1

Flow rate Q m3/hr 4,200 Measured

Water temp T C 20 Estimated

Water specific weight at working Temp S.G kg/m3 998.000 Physical

Gravity Acceleration g m/s2

9.806 Physical

Discharge pressure Pd Bar 8.20 Measured

Gauge correction gc m 0.50 Measured

Suction Pipe size Ds mm 1000 Drawings

Discharge Pipe size Dd mm 800 Drawings

Suction Pipe Length Ls m 20 Drawings

Vapor pressure @ 20C Hvp m 0.24 Physical

Atmospheric pressure @350 mASL Pa m 9.89 Physical

Zero Reference level LVL0

mASL 367.52 Drawings

water depth from Tank bottom H1 m 2.93 Measured

Suction pipe centerline depth H2 m 3.50 Drawings

Suction opening radius Rs m 0.70 Drawings

Discharge pipe depth from Ref. 0.00 H3 m 2.70 Drawings

Impeller Eye depth below ref 0.00 H4 m 2.09 Drawings

Friction Factor f 0.0104

Suction local losses factor Ks 0.99 Chimbar

Discharge local losses factor up to Gauge Kd 0.90 Bohl Pg 137-bild 4.71

Efficiency to test curve @ head tpc % 88.49% Curve

Net positive suction Head Required NPSHR mWC 5.28 Curve

Measured Motor Power Pm kW 1,170 Measured

Shaft Power to test curve Pact kW 1106.42 Curve

Motor efficiency m % 94.1% Data

Pressure @ collector Pd1 Bar 5.90 Measured

Voltage U V 6000 Measured

Current I A 117 Measured

Cos phi Cos() 0.962 Measured

Calculated power kW Pc kW 1170 Measured

Table 6

General calculations

Tank Bottom level LVL1 mASL 363.32 LVL0-(H2+Rs)

Water level in Basin LVL2 mASL 366.25 LVL1+H1

Pump Discharge pipe Centerline level LVL3 mASL 364.82 LVL0-H3

Impeller eye level LVL4 mASL 365.43 LVL0-H4

Suction pipe Area As m2 0.79 Ds2./4

Discharge pipe Area Ad m2 0.50 Dd2./4

Table 7

NPSHA Calculations

Velocity in suction pipe Vs m/s 1.49 Q/As

Suction Velocity head Hv mWC 0.113 Vs2/2g

Available positive head Hz mWC 0.82 LVL2-LVL4

Friction losses in pipe Hfs mWC 0.023 f x Ls / Ds x Hv

Suction Local losses HLs mWC 0.111 Ks x Hv

Suction total losses Hs mWC 0.135 Hfs + HLs

Net positive suction Head Available NPSHA mWC 10.45 =Ha+Hz-Hs+Hv-Hvp

NPSH difference mWC 5.18 NPSHA-NPSHR

Table 8


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It is known that the condition to operate the pump safely is to have an

NPSHA>NPSHR+(0.51.5)m; the operation of the pump at the rate of 5900 m3/hr is a result of

the hydraulic considerations in the design of the pumping station, this point will be discussed

further in the following clause 7

4. TECHNICAL MEASURES TAKEN BY THE ADMINISTRATION AND ITS SUITABILITY4.1. OPERATING THE PLANT IN MANUAL REGIMEBased on recommendations proposed to the administration, the pumps were operated by

applying a manual control regime in the year 2008; this was achieved by sliding the operation

point from the rightmost end of the curve which was causing cavitation, to another operation

point by partially closing the discharge side valve thus creating an extra local loss in the valve and

force the pump to operate at a point where there is no cavitation

This measures is considered to be good solution to save the pumps, but this came at the account

of the pumping economy as an unjustified extra cost of energy should be paid to overcome an

artificial loss created to solve a mechanical problem resulting from design considerations.

Clause 5 demonstrates the extra cost resulting from applying such a solution.

In addition, the use of butterfly valve for flow control is an impractical application due to high

potential of cavitation in the valve components as explained in clause 6-1 hereinafter.

4.2. CASTING PUMP FOUNDATION WITH CONCRETE:The fixing of pump foundation by casting concrete is an excellent technical solution, this has

resulted in increasing the structure inertia and stabilized the operation, especially that other

reasons such as entrained air and cavitation were eliminated.

Also this solution has resulted in maintaining the pump alignment during operation which will

save the rotating parts of the pump (Sleeves, bearings, wear rings, etc)

4.3. ERECTING A CONCRETE SLAB EXTENDING OVER THE SUCTION OPENINGS (BEGINNING OF 2009)This solution has reduced the flow velocity of the incoming water which resulted in increasing

the pressure within its bulk and eliminating the vortices and entrained air

4.4. INSTALLATION OF AIR RELEASE VALVES AT PUMP CASING CROWNAlso, this measures is a good solution to evacuate accumulated air which is produced naturally

due to local circulation in suction pipes during pump operation, even after solving the Vortices

problem in suction basin

4.5. REPAIR OF IMPELLERSThe administration has repaired the impellers by coating with Belzona (Figure 2-Impeller after

repair) in order to be able to operate the pumps and operate the plants


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Figure 2-Impeller after repair

There are few reservations on repairing the impellers of such size and importance resumed in

the following This material is used to repair the roughened surfaces subject to cavitation and

erosion for the purpose of increasing the smoothness of the surface.

This material has good resistance in locations with slow flow velocity, but it was used

to repair holes extending through the whole thickness of the impellers without any

metallic material to hold it in place, this is an unconventional use of this material and

there is a high potential for the collapse of such repair in the holes areas

As shown in the repaired impeller picture, the vanes ends are not neat and have notbeen properly machined; this results in local vortices at entrance area especially that

it is a high velocity area, and as Belzona has bad resistance to high velocities, this

area is subject to accelerated wearing.

It is not possible to restore the impeller to its initial dimensions and surface curvaturewhich will lead to a change in the pump performance.

The change in pump efficiency after repair according to available data is shown inTable 1, the lost power calculations due to repairs are shown in the following Table 9,

clause


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Flowrate of 4200 m3/hr Pressure at pressure gauge installed downstream the discharge taper equals 8.2 bars Consumed motor power of 1170 kW Motor efficiency of 94.1% according to contractor guaranteed values

The calculated efficiency and head of the pump at current operation setup are 86.14% and 83.06

m respectively.

Compared to curve values there is a loss of efficiency equal to 2.35% and in head equal to 2.78m

according to the following Table 9


Generated head calculations

Discharge measured Head Hdm mWC 83.61 Hd+GC

Discharge Corrected Head Hdc mWC 84.11 Hdm O 10.196

Velocity in Discharge pipe Vd m/s 2.32 Q/Ad

Discharge Velocity head Hvd mWC 0.275 Vd2/2g

Losses In discharge up to gauge location Hd mWC 0.247 KdxHvd

difference between Pipe C/L and water Hps mWC -1.43 LVL3-LVL2

Generated head Hp mWC 83.059 Hdc+Hps+Hs+Hd

Power losses Due to repair

Motor net output Pm_net kW 1101.0 P x Etm

Pump Hydraulic power Phyd kW 948.3 Q x Hp x SGx g/3.6x106

Power required (test curve efficiency) Ptc kW 1071.6 Phyd/Etpc

Pump Calculated efficiency P 86.14% Phyd/Pmnet

Pump head @ Q acc. To test curve Hpc mWC 85.75 From Curve

Lost Head due to Impeller repair HL mWC 2.70 Hpc-Hp

Lost Power /103m

3@ Motor eff. 94.1% PL1000 kw/10

3m

39.0396 HL x SGx g/3.6x106/Etp/m

Total Demand Volume V 103m

3/yr 46,426 Data

Total Irrigated area A Ar

Ha 6,656 Data

Irrigated Area by PS1 A1 Ha 755 Data

Pumped volume from PS1/year V1 103m

3/yr 46,426 Calculated

Irrigated Area by PS2 A2 Ha 2,840 Data



Irrigated Area by PS3 A3 Ha 3,061 Data



Total lost Power/season in PS1 P1 k.W.h 419,673 PLxV1

Table 9

According to above calculations, the total lost energy in PS1 due to reduced efficiency after

repairs is equal to

419,673 M.W.hr in PS1

The ratio of consumed energy in each plant to the total energy is estimated based on the

following table:

Description Unit PS1 PS2 PS3Total irrigated area by station Ha 6700 5945 3061Required head in station M 80.7 83.59 50.6Rate of consumed energy to total energy % 45.32 41.62 13.07Table 10


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Considering that the changes in the three plants are similar, the total lost energy in the three

plants due to reduced efficiency is equal to:

926,081 K.W.hr in three plants during the irrigation season

according to following table


Total lost Power/season in PS2 P2 k.W.h 375,590 PLxV2xH(PS2)/H(PS1)

Total lost Power/season in PS3 P3 k.W.h 196,557 PLxV3xH(PS3)/H(PS1)

Total Losses PL_Total k.W.h 991,821 P1+P2+P3

Table 11

Losses in PS1 are calculated based on current operation set point applied by administration; it

may vary towards increase-decrease depending on the change in operation parameters

5.2. LOSSES CAUSED BY PARTIAL VALVE CLOSUREPump operation points were selected based on the engineer and contractor calculations, the

pumps were also supplied based on this basis, it was found out, according to current

measurements, that the actual losses in the system are less than the calculated losses, the

required pressure in the collector is 5.9 to 7.29 bars to pass a flowrate of 4200 to 16800 m3/hr in

the main pressure pipe respectively. These measurements confirm the measurements made at

the startup phase, which showed that the pump operated at 6.22 bars at startup which resulted

in operating the pump at the end of the curve (even outside the curve) when one pump was

operating; This caused NPSHR to exceed NPSHA by approximately 1.75m as mentioned in clause


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L BAB TADEF IRRIGATION PROJECT Technical evaluation and Feasibility studyof Pumping stations performance

age 11 of 24 CASE STUDY-AL BAB-TADEF PS P ERFROMANCE FEASIBILTY.DOCX

Figure 3 - Pump operation curves

30

40

50

60

70

80

90

100

110

120

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

105

110

115

120

1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000

Efficiency%

NPSHRx10mWC

HmWC

Q m3/hr

Pump Operation Curves

Suggested Operation Point

Q=5363 m3/hr

H=71.15mNPSHR=8.44m

Operation Point at startupQ=6070 m3/hr

H=59.5 m

NPSHR=12m

Actual Operation Point

Q=4200 m3/hr

H=83.06 m

NPSHR=5.28m

NPSHR=8.44m

H=71.15m

Saved Head 11.91m

Flowrate = 5363 m3/hr

Efficiency 87.49

=88.49%

Q=5363m

3/hr


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6. OTHER TECHNICAL REMARKS6.1. DISCHARGE VALVESThe use of a butterfly valve as a control valve is not recommended as the partial closure shallforce the flow to pass through a small cross section, thus increasing the flow velocity; this in

turn, shall result in a pressure drop on the downstream face of the disk causing:

Cavitation on the downstream face of the valve disk Excess torsion on the valve shaft causing wear of the gear box

Figure 4

For those reasons, it is not recommended to use this type of valve for control

The following Figure 5 shows the opening ratio (23%)at a flowrate of 4200 m3/hr under a

deferential pressure of 22.4 m

According to Figure 6 It is clear that the valve will be subject to wear due to cavitation

Fowra

tem3

r

Opening %

Opening degree @

4200 m3/hr flow

and P=22.4 m

Cavitation areas


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Figure 5

Figure 6

Remark: the area where the cavitation no. in the valve (Red curve) is greater than the audible,

visible and full cavitation lines is considered as cavitation area. At an opening degree of 23% all

cavitation lines are below the red line, which means audible, visible and full cavitation will occur.

6.2. NON RETURN VALVEHydraulic piston of one or more non-return valves required repair and calibration, it is very

important to calibrate the NRVs pistons to facilitate the self-opening of the valve. This should be

calibrated according to manufacturers recommendations by modifying the location of the

counterweight and the piston throttling valve.

6.3. PUMP PACKINGOne of the pump packing is not passing cooling water, this will cause overheating of bearing

areas.

This should be repaired to guarantee proper cooling of the bearing area

7. TECHNICAL RECOMMENDATIONS AND PROPOSALS FOR IMPROVING PERFORMANCE7.1. IMMEDIATE MAINTENACE MEASURES

Cavitation no.@ 23% opening

CavitationNumber

Opening %


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Calibrate NRVs on pump discharge pipe (Counter weight and hydraulic piston Repair of packing of pump in PS1

7.2. MEASURES DURING MAINTENANCE PERIOD Check the control valve for cavitation evidence on valve disk and body Check repaired pumps impellers and durability of Belzona Installation of the following instruments if not available Accurate pressure gauges in the following locations Directly at the centerline of the pump suction flange Directly at the centerline of the pump discharge flange at the centerline of the main pressure pipe Level measurement in suction and discharge basins

The purpose of those measurements is to evaluate the performance of the pumps and

calculating the actual losses in system accurately according to flowrate

7.3. MEASURES REQUIRED FOR REDUCING ENERGY LOSSBefore making future decisions to be applied to improve the plant performance, measurements

of different operation parameters should be carried out during at least one irrigation season,

readings should be made at every change, start and stop of all pumps including direct irrigation

pumps

The records should be made for the following parameters:

Tag of each operating pump Pressure at pump discharge flange Pressure at pump suction flange Pressure at the beginning of the main pressure pipeline Variation in water level at suction basin Variation in water level at discharge basin (the levels of PS2 suction basin should be

transmitted to PS1 and in PS3 to PS2)

Power withdrawn from the motor Enhanced Power factor Withdrawn current Actual voltage

7.3.1. IMPROVING EFFICIENCYIt is recommended to replace the impellers by new impellers of the same material, as the change

to a higher grade will not contribute to eliminating the cavitation and this phenomenon should

be eliminated by applying different approach.

Due to the great effect of the efficiency on pumping cost, especially in a plant of this size, it is

advised to replace the impellers by original impellers made by the manufacturer in order to

guarantee the efficiency and to warrant the performance of the pump unless there is another

supplier who can guarantee the test curve efficiency as minimum and guarantee the

performance of the pump.

7.3.2. REDUCING LOCAL LOSSES IN DISCHARGE VALVEA program was developed to calculate the consumed energy required during the irrigation

season, the following figure shows the user interface of the program


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L BAB TADEF IRRIGATION PROJECT Technical evaluation and Feasibility studyof Pumping stations performance

age 15 of 24 CASE STUDY-AL BAB-TADEF PS P ERFROMANCE FEASIBILTY.DOCX

Motor Power kW m3/hr

Total Consumed Power kW

2 Lost Power/Pump kW m3/hr

5 Total Lost power kW m3/hr (24 hrs operation)

% lost power

31 Net kW/m3 Level mASL

Daily Op. hrs 744 Motor efficiency P mWC

D1/D or N1/N Pg m Gauge correction m

D Pg Bar P @ Collector mWC

Gauge correction m P @ Collector Bar H

Level Min. Hs Hst

NPSHA-NPSHR Level f

m3/hr

f mm 3

Ds NPSHA mWC m 4

L= [m] NPSHR mWC 5

= mm Vs m/s Hpump Curve mWC Dd mm 6

= m/s

2

Kfs pump curve Vd m/s m/s 7

Ks Kd mWC 8

Hs mWC QPump m3/hr Hd mWC mWC 9

Trim Ns 10

62.95

V pipe 1.940.21

1400

98.74%

0.8704

0.8754

0.8866

0.8932

0.8704

0.8704

0.8704

0.8704

2.96

421.24

19.46

Op. hrs

94.1%

May Qmin

7.85

603 0.231

54.99

8.44

800.00

Month All 274.96

Volume 6,469,100 11.1%

6.97 63.41

0.50 6.22 56.42

71.61 1.00

0.0111

27.89

L pipe 3509

K pipe 3.496

10725

5.99

0.220 5363

49.40

5363

1.75 Total Head

0.99 3.90 H pipe

D pipe

1000

Variable NRPM 988.00

2.00 364.82

2.00

QBEP

100.00%

88.49%

10.44

70.80

790.00

0.0104

4347.51

Kf pipe

Q pipe

4750.00

1,239.52 Recomm end ed flow 53 63

2,479.05 1,495,304

137.48

PS1 Operation System

366.25

4.60E-02

1.00E-06

1.90

20.00

No of Operating pumps

Start

Figure 7


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The total consumed energy required for PS1 during the irrigation season when pump operates at

current designated flow rate of 4200 m3/hr and at calculated efficiency is shown in the following

Table 12

Q Pump 4200 m3/hr - N=988 rpm (Reduced=781.73 mm)

1xPumps 2xPumps 3xPumps All pumps

Month

Mar 530,741 530,741 530,741

Apr 2,130,845

May 1,801,373

Jun 1,324,235 1,324,235

Jul 2,276,673

Aug 2,362,160

Sep 1,799,953

Oct 701,714 701,714 701,714

Total 12,927,696

Total losses under current operation conditions 991,821

Table 12

The above table is shown in graphical form in the following Chart

Chart 1

It is proposed to use one of the following methods to reduce losses in valves:

7.3.2.1. CHANGE OF PUMP OPERATION POINTThe purpose of the pumping process is to supply the maximum volume of water with minimum

required head, this implies that minimizing the required head and increasing the flowrate is the

right approach to reach an economical cost of pumping, at the same time, consideration should

be made not to operate the pump in under cavitation conditions

This can be achieved by shifting the operation point to the right side of the curve.

Two operation pints were investigated

531 7

02

531

1,324

702

531

2,131

1,801

1,324

2,277

2,362

1,800

702

12,927.70

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

-

500

1,000

1,500

2,000

2,500

3,000

Mar Apr May Jun Jul Aug Sep Oct Total

PumpingEnergyin1000kW

MonthlyPumpingEnergyK.W.hr

Month


991,821Energy Lost in 3 plants kW.hr


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a. Operating the pump at best efficiency pointOperation at BEP Q =4750 m3/s

1xPumps 2xPumps 3xPumps All Pumps

Month

Mar 491,181 491,181 491,181

Apr 1,972,015

May 1,667,102 1,667,102

Jun 1,225,529 1,225,529

Jul 2,106,974

Aug 2,186,088

Sep 1,665,788 1,665,788

Oct 649,410 649,410 649,410

Total 11,964,086

Saved energy in PS1 963,610

Total Annual Saved energy in 3 Plants kW.hr 2,277,316

Total Annual Savings in Syrian Pounds (3.00 SP / kW.hr) 6,831,948

Table 13

The total consumed energy required for PS1 during the irrigation season when pump operates atBest efficiency point is shown in the following Chart 2

Chart 2b. operating the pump at maximum possible flowrateThe other possibility is to operate the pump at the maximum possible flowrate by shifting the

operation point to the leftmost side of the curve without causing cavitation by opening the valve

to the maximum possible opening

it is advisable to operate the pump at a point where the NPSHA NPSHR 2m, this will

guarantee sufficient positive pressure without cavitation

According to Figure 3 - Pump operation curves, to achieve a suction pressure of +2 m, the pump

should operate at a flowrate of 5363 m3/hr, where NPSHR is 8.44m and NPSHA is 10.44 m, the

pump head in this case is 71.15 m

491 6

49

491

1,667

1,2

26

1,666

649

491

1,972

1,667

1,2

26

2,107

2,186

1,666

649

11,964.0

9

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

-

500

1,000

1,500

2,000

2,500

3,000


PumpingEnergy

in1000kW

MonthlyPum

pingEnergy

Month


2,277,316Energy Saving in 3 plants kW.hr


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This can be realized by changing the pressure set point at the discharge valve to a value of 6.84

bars

In all cases, the performance of the pump should be closely monitored during valve opening for

vibration and cavitation.

As a better Measures, and in order to guarantee the pressure in the suction pipe

above the 2 m set point, it is recommended to control the discharge valve using a

pressure sensor with a range from -5 to +5 m, installed at the suction side and the

valve shall continue to open until the suction pressure is in the range of 2 m., by this

we guarantee the maximum flowrate without cavitation

As mentioned above, it is always necessary to monitor the pump operation during the first

calibration

Calculation of energy saving when operating the pump at 5636 m3/hr

Q Pump 5363 m3/hr Impeller Dia=790@N=988 rpm


Month

Mar 440,563 440,563 440,563

Apr 1,768,795 1,768,795

May 1,495,304 1,495,304

Jun 1,099,236 1,099,236

Jul 1,889,846

Aug 1,960,808

Sep 1,494,125 1,494,125

Oct 582,487 582,487 582,487

Total 10,731,165

Saved energy in PS1 2,196,531



Table 14


5363 m3/hr is shown in the following Chart 3


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Chart 3

7.3.2.2. CHANGE OF IMPELLER DIAMETERIf sufficient measurements were made according to requirement of clause


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It is worthy to indicate that the pump operation curves with the new impeller size should be

obtained by the manufacturer to carry out an exact calculation of consumed energy

Also, the above table clearly indicate that operating less number of pumps for longer periods of

time is more feasible than operating many pumps for shorter time despite of the losses in valves

due to valve closure to avoid cavitation, so it is advisable to operate the minimum number ofpumps for longer periods

In all cases, the number of required pumps is related to many factors, such as water demand,

reservoir volumes power availability, water levels in suction and discharge tanks

The above table is shown in graphical form in the following

Chart 47.3.2.3. CHANGING PUMPING SPEEDOne of the proposed technical solutions to reduce losses in valves, is to reduce pump rotating

speed to cope with required head

The effect of changing pump speed is hydraulically similar to changing impeller diameter except

that it has the following advantages

Maintaining the impeller diameter to produce any extra required head if necessary(Better maneuverability)

Maintaining the efficiency at its optimal values as the change in diameter will reducethe efficiency due to local circulation caused by reduced diameter, and because the

losses inside the pump are inversely proportional to rotation speed

The pump speed can be change by changing the electrical frequency using Variable frequency

drives (VFD)

The minimum rotation speed, which gives the least cost of pumping, was estimated to be theequivalent to the minimum impeller trim on the pump commercial curve, i.e. by reducing the

speed by approximately 13%

367

486

389

1,322

972

1,321

515

418

1,677

1,418

1,042

1,792

1,85

9

1,417

552

9,795.06

0

2,000

4,000

6,000

8,000

10,000

12,000

-

500

1,000

1,500

2,000

2,500

3,000



PumpingEnergyK.W.hr

Month




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860 rpm speed is shown in the following Table 16

The decision to install VFDs should be made taking into consideration the following factors:

Pump operation characteristics at 860 rpm (Q, H, , NPSHR) which should be suppliedby the manufacturer

Ability of the existing motor to run at 860 rpm without considerable reduction inefficiency

The initial and O&M cost and Power loss of the VFD Saved energy during the lifetime of the plant

Impeller D=790, N=860 rpm


Mont

h

Mar 355,475 370,311 390,253

Apr 1,566,805

May 1,324,545

Jun 923,952 973,707Jul 1,674,032

Aug 1,736,891

Sep 1,323,501

Oct 469,987 489,603 515,969

Total 9,375,188

Saved energy in PS1 3,552,508



Table 16

Cost of lost energy was calculated based on energy unit price of 3.00 SYP/k.W.hr

The relatively high savings in energy is a result of two reasons1- Increasing the useful energy by increasing the flowrate and reducing the head, either by

reducing the impeller size or pump speed accompanied by shifting the operation point to

a higher efficiency point. Which is the main factor in increasing pumping economy

2- The increase of efficiency after replacing the impellers with original impellersTable 16 is shown in graphical form in the following Chart 5


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Chart 5

355 4

70

370

924

490

390

1,567

1,325

974

1,674

1,737

1,324

516

9,375.19

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

-

500

1,000

1,500

2,000

2,500

3,000



MonthlyPumpingEnergyK.W

.hr

Month




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8. CONCLUSIONSFrom discussion and calculations shown in this report, one can conclude the following

There are some design and execution blunders, which caused operational problemssome of those problems are corrected by the administration in a good way

There are still minor repair works which needs to be tackled There are major energy losses estimated at 8400 M.W.hr annually caused by 2

reasons

The method of impellers repairs which resulted in efficiency loss The difference between the actual operation conditions and the design

considerations, forced the administration to operate the pumps at non economical

operation points to avoid deterioration of pumps due to cavitation

A considerable amount of energy can be saved by applying one or more of the following

solutions

I. It is important to change the impellers by new impellers from the manufacturer with thesame material, but the decision of changing the impeller diameter should be made in

light of operation parameters

II. Modify the operation points as detailed in


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V. All measurements of operation parameters and required instruments mentioned inclause

Case Study-Al Bab-Tadef PS Perfromance Feasibilty

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