Energy saving opportunities for South Kamlapur (MODS ZONE-1) of DHAKA WASA Introduction DWASA is taking the initiative to optimize its pump operations, meaning maximizing the volume of water to be drawn from DTWs (Deep Tube Well) whilst optimizing energy consumption. The maximum volume of water that can be drawn from DTWs is defined by geo- hydrological conditions and DTW construction. This volume is determined by i) pump tests and ii) the maximum flow velocity in the gravel pack and amounts for new DTWs approximately 110 m 3 /h. This volume will however reduce in time, due to well clogging. The benchmark for the specific energy consumption by DWASA´s DTWs is 0.35 kWh/m 3 – 0.40 kWh/m 3 . At the moment the specific energy consumption of South Kamlapur is 0.396 kWh/m 3 – 0.421 kWh/m 3 . From the time of starting only single time stopped working of the pump due to: 1. Sucking air with water. 2. Hole creation in the column pipe. This report presents seven six options for South kamlapur that aim to 1) minimize energy consumption, 2) maximize the volume of water abstracted and 3) reduce the downtime of DTW. For each DTW these options need to be investigated before implementation. Combinations of the various options will –in most cases- result the best operations. The options are: 1. Improvement of pump selection; 2. Adjustment of Variable Frequency Drive (VFD) settings; 3. Prevention of pumping of air; 4. Stop the pump when water supply is sufficient; 5. Continuation of abstraction from abandoned DTWs; 6. Operational measures: reducing downtime. 1. Improvement of pump selection Pump data of existing pump-motor of running DTW- Brand of running pump: CRI Pump head at 0 lpm: 118 m Pump head at 97 m 3 /hr: 98 m The pump curve of the running pump given below at fig-1, which is operating out of operating range at Best Efficiency Point. [email protected]+88-01811410155 +88-01832864188 Facebook: WOPDWASAVEI Dhaka WASA Bhaban 98, Kazi Nazrul Islam Avenue 11th floor, Room #1202
Transcript
Energy saving opportunities for South Kamlapur (MODS ZONE-1) of DHAKA WASA
IntroductionDWASA is taking the initiative to optimize its pump operations, meaning maximizing the volume of water to be drawn from DTWs (Deep Tube Well) whilst optimizing energy consumption.
The maximum volume of water that can be drawn from DTWs is defined by geo-hydrological conditions and DTW construction. This volume is determined by i) pump tests and ii) the maximum flow velocity in the gravel pack and amounts for new DTWs approximately 110 m3/h. This volume will however reduce in time, due to well clogging.
The benchmark for the specific energy consumption by DWASA´s DTWs is 0.35 kWh/m3 – 0.40 kWh/m3. At the moment the specific energy consumption of South Kamlapur is 0.396 kWh/m3 – 0.421 kWh/m3.
From the time of starting only single time stopped working of the pump due to:1. Sucking air with water.2. Hole creation in the column pipe.
This report presents seven six options for South kamlapur that aim to 1) minimize energy consumption, 2) maximize the volume of water abstracted and 3) reduce the downtime of DTW. For each DTW these options need to be investigated before implementation. Combinations of the various options will –in most cases- result the best operations.
The options are:1. Improvement of pump selection;2. Adjustment of Variable Frequency Drive (VFD) settings; 3. Prevention of pumping of air;4. Stop the pump when water supply is sufficient;5. Continuation of abstraction from abandoned DTWs;6. Operational measures: reducing downtime.
1. Improvement of pump selectionPump data of existing pump-motor of running DTW- Brand of running pump: CRIPump head at 0 lpm: 118 mPump head at 97 m3/hr: 98 mThe pump curve of the running pump given below at fig-1, which is operating out of operating range at Best Efficiency Point.
DWASA is recommended to review the pump that is installed in its South Kamlapur DTW.Pumps installed should meet the following technical requirements:
The existing pump may replace to the new pump which capacity may be: 95 m3/h which are available in measurement by Clamp on flow meter at 50 Hz for best longevity of well.
The operating range of the new pump should be between 65% and 115% of the pump’s Best Efficiency Point (BEP) which shown below fig-2.
The operating point should be close to best efficiency point which shown below fig-2.DWASA is furthermore advised to monitor flow and water levels regularly and review/adjust the pumping settings accordingly via the Variable Frequency Drive for South Kamlapur.
The only way we can save energy with a Variable Frequency Drive is when there is a possibility to decrease the frequency of the motor. The brand of running VFD is ABB. The VFD is running at full speed. When the frequency of the motor decreases, indeed energy consumption will reduce, but production will also reduce, as will the total pump head, as illustrated in the three examples below:
For situation when needed to reduce the DTW capacity, authority is advised to determine the required capacity and adjust the VFD settings accordingly, in order to reduce the specific energy consumption.The use of VFD does consume 3% more energy than a star/delta starter.
Be careful: The Minimum frequency setting was 0 Hz. The frequency can only be set between 40 and 50 Hz. Lower frequencies will burn/damage the pumps, as the motor cannot be cooled enough by the water. Running VFD produced huge sound and heat. The driving temperature of VFD was 48.5 0C. So Running VFD to be changed by a soundless VFD and to be ensured air circulation. Round and inside of VFD box, huge dusts are available. So to be kept surrounding of VFD neat and clean. Accel/Deceler time setting was 15 sec but it is better to control starting current recommended Accel/Deceler time within 30 sec.
Parameter settings to be made:No Name Default Change in26 Motor control
9905 Motor nominal volt (V) 4009906 Motor nominal current (A) 909907 Motor nominal frequency (Hz) 509908 Motor nominal speed (rpm) 28009909 Motor nominal power (kW) 50
20 Limits2007 Minimum frequency (Hz) 0 402008 Maximum frequency (Hz) 50
30 Fault functions3005 Motor therm. protection 0 1
31 Automatic reset3101 Number of trials 0 23103 Delay time (s) 0 603104 AR over current 0 (Disable) 13105 AR over voltage 0 (Disable) 13106 AR under voltage 0 (Disable) 1
By using a Variable Frequency Drive at a centrifugal pump can save energy according to the affinity laws, for example:
Frequency Capacity m3/h Head (m) Power (kW)50 95.01 85 40
47.5 90.3 76.7 34.3Explanation 47.5/50=0.95
95.01 x 0.95 = 90.3 85 x 0.952= 76.7 40 x 0.953= 34.3
45 85.51 68.85 29.16Explanation 45/50=0.9 95.01 x 0.9 = 85.51 85 x 0.92= 68.85 40 x 0.93=29.16
From the above table, it is seen that the measured capacity is not same as the affinity law calculation.
In summary:Frequency (Hz) is going down -> capacity (m 3 /h) is going down –>head (m) is going down - >power consumption (kW) is reduced
3. Prevention of AirThe main cause of first time interruption of pump were sucking air and vortex problem. To avoided air suction, the following action can be taken:
Lower the pump deeper in the well. Housing pipe length of running well 360 ft and column pipe length 260 ft. So the pump should be installed deep inside the well (Keeping gap minimum single meter between the bottom of housing pipe and bottom of pump-motor) in order to accommodate for the declining water levels (2m/year) and to avoid early replacement.
Reduce frequency by adjust VFD settings;
Furthermore, DWASA is advised to monitor the flow by using the clamp-on flow meter, as mechanical meters do not indicate air suction.Running DTW:Date of commissioning: 5.5.2014SWL: 190 ft (5.5.2014)SWL: 165 ft (26.01.2016)Housing pipe length: 360 ftTotal fixture length: 912 ft
Sl no.
Date of work
Description of work PumpBrand
PumpCapacity
Head Column pipe
Production
01 5.5.14 New well CRI 1.5 cusec
75 m 240 ft 120 m3/h
02 4.7.15 Sucking air, leakage found in column pipe
CRI 1.5 cusec
75 m 260 ft 126 m3/h
Housing pipe length: 360 ft. Total column pipe installed 260 ft. FMD-1 could be extending more 80 ft column pipe. In summary:Lower the pump as much as possible -> Air suction is stopped -> longer pump life -> capacity will stay as high as possible.
The water consumption during nighttime differs from the water consumption during day time. DWASA is advised to turn of the pump 2 times per day by a period of 15 minutes, which is beneficial for the well performance over a longer period of time.
In summary:Capacity is going down –> power consumption is decreasing –> energy saving
5. Continuation of abstraction from abandoned DTWsOne DTW of South kamlapur have been abandoned. When it declared to abandoned, the capacity was 40 m3/h. By installation of a low capacity pump (e.g. 30 – 40 m3/h) and sufficient head. The discharge and head of the pump will be Q=35m3/h and 98 m respectively. At present the static water level of DTW is 78 m. The appropriate pump curve at the best efficiency point given below in fig-3. Those DTWs will be useful e.g.during night time when water demand is low (the new DTW with the bigger capacity may be stopped during night time to get its rest). In cases where pumps are operated in parallel, it is important to install check valves in both delivery lines and the head of both pumps must be equal.
Evidently, the operation of the abandoned DTW will increase energy consumption. This measure is recommended for that times when water supply is insufficient.
Abandoned DTW:Date of commissioning: 24.9.2008Total interruption occurs 08 times, among last 05 following:
Sl no.
Date of work
Description of work PumpBrand
PumpCapacity
Column pipe
Production
01 5.5.10 Sounding problem China 1.0 cusec 290 ft 1400 LPM02 27.1.12 Production low China 1.0 cusec 290 ft ……………03 12.5.12 Motor burning Spain 1.0 cusec 310 ft 800 LPM04 15.1.14 Pump felt down into well China 1.0 cusec 310 ft 1000 LPM05 1.5.14 Production low China 1.0 cusec 310 ft 670 LPM
In summary:Capacity increases –> power consumption increases
6. Operational measures: reducing downtime and parallel operation
FMD-1 observed the following downtime events for South Kamlapur:
Sl no.
Date of work
Description of work PumpBrand
PumpCapacity
Head
Column pipe
Production
01 5.5.14 New well CRI 1.5 cusec 75 m 240 ft 120 m3/h02 4.7.15 Sucking air, leakage
found in column pipeCRI 1.5 cusec 75 m 260 ft 126 m3/h
To reducing downtime of DTW South kamlapur pump stops can easily be solved by:- Installing the pump deeper in the well (hence, downtime due to adding extra column
pipes at a later moment is not necessary anymore). There has a scope to extend more 80 ft column pipe. Negligible friction loss 0.616m will occur for extend 80 ft column pipe.
Pipe friction loss formula is
- When it will be necessary to extend cable, carefully maintain to proper jointing. One of the best method of cable jointing is 3M Scotchcast Resin Cable Joint method
If these issues can be tackled, the number of downtime events could strongly reduce and therefore increasing the production of the total volume of water.
In summary:Capacity is going up (less pump stops) –>more water ->more power consumption.
