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Leakage 2005 - Conference Proceedings Page 1

A Case Study of Leakage Management in the City of Busan, Korea


E Shin*, H Park**, C Park***, I Hyun****

*Graduate, Department of Civil and Environmental Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejon, South Korea, [email protected]

** Professor, Department of Civil and Environmental Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejon, South Korea, [email protected]

*** 709-18, Yeonsa-5-dong, Yeonje-gu, Busan, South Korea,

**** Professor, Dankook University, Hannam-ro 147, Yongsan-gu, Seoul, South Korea, [email protected]

Keywords: Block system; Water losses, Leakage management

Introduction

Leakage reduction as a whole is complex and requires co-ordinated actions of various water network management options. One of them is operational pressure control which is to reduce risks of further leaks by smoothing pressure variations. It is also known a cost-effective means of reducing leakage. It however can not remove the original causes and is thus not suitable to serious leakages.

In some parts of Korea, water losses is almost 30% of which main causes include breaks of aged pipes. Korea is now in timely need of fixing this leakage problem, considering as options operational pressure control coupled together with creating block system. Block System was initially developed in Japan to build her water distribution networks more resistant to earthquake. The block system approach basically converts a large network into a group of small and simple sub-networks which can be more or less independent each other. It was moreover proved that such a block system can also cope with leakage management. Since it is easier to search causes of water losses and fix in small and simple networks than large and complicated networks, the block system approach has recently been adopted to manage leakage in many places of the world. As a test case to the entire city networks, the City selected a system in the Namhang-dong area and made it blocks for pressure and leakage management. This study is to introduce the results of the test case.

Methodology

Block system, which divides large networks into some sub-networks, is known an ideal water network system for leakage management. Its positive attributes include the followings:

• Water losses are efficiently controlled by checking flow quantity in small area.

• Physical losses are reduced, because water pressure fluctuation becomes less sharp.

For carrying out the block system approach, the activities shown in Table 2.1 have been conducted, which are classified into two groups: creating small blocks and leakage detection & repairing.



Table 2.1 Major tasks and activities of leakage management

Tasks Creating Small Blocks Leakage Detection and Repairing

1.Determine a main input line 1.Estimate the current situation

2.Develop blocks 2.Check metering devices

3.Check pressure distribution 3.Measure minimum-night-flow and conduct a series of tests

4.Establish facility plan for blocking andisolation (i.e. blocking plans) 4.Leakage detection along lines

5.Checking isolation of blocks 5.Implement leakage control measures

6. Install meters and measure flows 6.Estimate daily input, leakage and pressure distribution after leakage control

7.Check pressure distribution afterisolation

7.Estimate the effect of the leakage manage plan

Activities

8.Evaluate the feasibility of blockingplans 8.Report the plan

Creating Small Blocks

Creating small blocks is composed of checking present condition, developing a blocking (facility) plan, isolating and checking isolation of each block, and evaluating feasibility of the plan.

To understand the actual condition of a project area, initial water pressure, status of pipeline, the amount of average daily consumption investigated. By considering all these results, a main input line is decided.

Major factors to be considered for developing blocks in a project area are as follows: administrative manageability, possibility of block isolation, whether suitable input line exists or not, whether water pressure is within an appropriate range, and the possibility of interconnecting with nearby blocks in emergency using emergency valve and others. To check that a proposed plan can works, we install a water pressure measurement device to highest fire hydrant in each small block. After closing side connections of each small block, we check whether the water pressure is dropped to zero or not.

Comparing water pressures before and after block isolation is a reasonable method to examine the feasibility of the blocking plan. If the pressure drop is significant, we must repeat the whole process again to develop another blocking plan.

Leakage detection & repairing

System inputs are shown in Table 3.6. Water losses are made up of commercial losses and physical losses and commercial losses are classified with unauthorized consumption and metering inaccuracies & data handling errors, according to IWA recommendation. In



this research, we aim at reducing water losses in two ways. First is decreasing metering inaccuracies by checking metering devices. The other is minimizing physical losses by applying the block system approach.

First step of leakage detection & repairing is estimating the current situation. In this study, we ignore the billed unmetered consumption and unbilled unmetered consumption, because these values are known very small compared with other items. In this test project area, unbilled meter consumption is almost 2% of the total system input volume. We assume that the volume of commercial losses is equal to each those of metering inaccuracies and data dandling errors because unauthorized consumption has not been checked in this study.

Metering inaccuracies and data handling errors are calculated as shown in Table 2.2. Just to save time and effort, only 5% of the whole metering devices are inspected as a sample and the results have been extended to cover the whole devices.

Table2.2 Remedial method to metering device inaccuracies

Classification Remedial method

Damaged metering device - Replace the damaged metering device

Expired metering device - Replace the expired metering device

(below D=50mm: 8 year, above D=50mm: 6 year)

Sealing of metering device - Check the sealing existence

Non-standardized protection cover - Use a choice of brands

Metering device which measures below the minimum

- Observe the metering device if its measurement is below 10m3/month

Unproper metering device - Replace the unproper metering device

A series of tests have been conducted to reduce the physical losses. In the first place, acoustic emission test is preformed in order to find segments of pipelines with water leakage possibility by using the Pocus instrument. With each of the 60 devices installed, as shown in Fig 3.3, sound pressures have been analyzed. In the segments with leakage possibility, hearing and other direct detection methods are carried out to pinpoint out the portions being replaced or repaired.

Creating Small Blocks

Understanding the present condition

Fig 3.1 shows the project area. Average daily consumption for a period of for 14 months from January 2004 to February 2005 is calculated. To supply the average daily consumption (i.e. 2389m3/day), the pipeline as shown in Fig 3.1 is selected as a main input line.



Table 3.1 Average daily consumption of the 14 months (January 2004 to February 2005)

Year 2004 2005

Month 1~2 3~4 5~6 7~8 9~10 11~12 1~2

Total consumption

[m3] 147,442 137,053 143,674 149,719 144,927 144,628 152,686

2,457 2,247 2,355 2,415 2,376 2,371 2,503 Average daily consumption

[m3/day] 2,389

Developing 2nd blocks & checking isolation of each block

Evaluation results for selecting a block, called the 2nd block here, are appeared in Table 3.2. With these evaluation, we also divided it into three small blocks(2-1, 2-2, and 2-3). After isolating the 2nd Block by closing off the side boundaries, we set up a water pressure measurement device in a hydrant at the highest point in the block and measure pressure change before and after blocking. By confirming that the water pressure is dropped to zero, we conclude that the 2nd block is appropriately isolated.

Table 3.2 Factors and evaluation results for selecting the 2nd Block

Considering factors Results

Administration section to be managed Namhang-dong , Yungdo-gu, Busan, Korea

Possibility of block isolation Possible

Whether suitable input line exists or not

D = 400mm pipeline is possible

D = 200mm pipeline is possible

Whether water pressure is within appropriate range

Pressure head : 0.3m ~ 11.2m

water pressure at the exit : 6.7kgf/㎠

Feasibility of interconnecting with nearby blocks in

emergency Installation of emergency valve is possible.

Whether the construction of emergency storage tank is

possible or not Water in side pipeline can be used in emergency.



Figure 3.1 Project area with proposed 2nd block & small blocks

Evaluating the plan of small blocks

To evaluate feasibility of the proposed plan of small blocks shown in Fig. 3.1, the water pressures before and after isolation are measured in 8 locations as shown in Fig. 3.2. The results are summarized in Table 3.3, showing that after blocking, pressure drops are in a range of 0.1~0.8kg/cm2 through the project area and the daytime pressures in the blocked network are also maintained around 2.6 kg/cm2. We think these results confirm that our blocking scheme works out reasonably well.

Table 3.3 Water pressures before and behind isolation

Water pressure before isolation(㎏/㎠)

Water pressure behind isolation (㎏/㎠) difference

NO maximum

(time) minimum

(time) maximum

(time) minimum

(time) maximum minimum

1 7.04(02:00) 5.09(09:00) 6.42(03:00) 3.02(10:00) -0.62 -2.07 2 7.04(02:00) 5.09(09:00) 6.94(04:00) 3.77(10:00) -0.1 -1.32 3 7.48(02:00) 5.53(09:00) 6.70(03:00) 2.97(10:00) -0.78 -2.56 4 7.66(02:00) 5.63(09:00) 6.87(03:00) 3.05(10:00) -0.79 -2.58 5 6.87(03:00) 4.87(09:00) 6.61(04:00) 4.53(09:00) -0.26 -0.34 6 7.18(03:00) 5.38(09:00) 6.59(03:00) 2.73(10:00) -0.59 -2.65 7 6.61(03:00) 3.26(09:00) 6.40(04:00) 3.54(11:00) -0.21 0.28 8 7.23(03:00) 3.83(09:00) 6.87(04:00) 3.57(11:00) -0.36 -0.26

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Flow-Meter



Figure 3.2 8 pressure-measuring locations.

Leakage Detection and Repairing

Estimating an initial Water losses

After having the blocks, average daily system input volume is measured 3235m3/day for 11 days from December 30, 2004 to January 9, 2005 and average daily consumption (i.e. billed metered consumption) is 2180.4m3/day for the same 11 days. This results in that the amount of average daily unbilled metered consumption is 413m3/day. As mentioned before, we assume that billed unmetered consumption and unbilled unmetered consumption are zero. All these indicate that water losses in this area is 22.63% of the system input volume, as shown in Table 3.4.

Table 3.4 An initial water losses condition

Duration

Average daily system input volume

(㎥/day)

Average daily consumption

(㎥/day)

Average unbilled metered consumption

(㎥/day)

Water losses

(㎥/day)

2004.12.30~

2005~1.9 3,235 2,180.4 413 641.6

Commercial losses

We check the factors, shown in Table 2.2, with the 5% of the whole metering devices in the 2nd block to calculate the metering inaccuracies and data handling errors. We find that the average daily billed metered consumptions, before and after repairing and replaind, are 112m3/day, 118.3m3/day, respectively. This indicates that an error of 6.3 m3/day exists with the 5%. If we assume the same results with the rest 95% devices, the initial amount



of metering inaccuracies and data handling errors will amount to 122.7m3/day and this value will decrease to 116.4m3/day by repairing and replacing damaged metering devices.

A Series of tests for reducing physical losses

Initial physical losses can be calculated by subtracting initial commercial losses from initial water losses. The above figures indicate that the amount of initial physical losses is 518.9m3/day. To reduce this, we conduct a series of tests discussed previously. By analyzing the data of 60 instruments, we identified the 29 sections to have potential for reduction which are displayed with red color in Fig 3.5

Figure 3.3 29 locations with possible water leakage and potential for reduction

Electric leakage detector is used to find the leakage points, Then, we confirm the leakage spots by direct test. Nine leakage spots among 29 points are identified and then repaired or replaced as explained in Table 3.8. The 9 point are shown in Fig 3.6. By doing all these, physical losses are reduced up to 40.5%, as shown in Table 3.6.



Figure 3.4 9 leakage spots

Table 3.5 Repairing and replacing

Repairing and replacing No.

material Diameter Leakage point reason

1 DCIP 25mm Valve External load

2 DCIP 25mm Valve External load

3 EP 13mm Connection failure Old age

4 PFP 40mm Connection failure Old age

5 DCIP 13mm Connection failure Old age

6 PFP 40mm Connection failure Old age

7 EP 13mm Metering device Old age

8 EP 13mm Metering device Old age

9 PVC 16mm Connection failure External load



Table 3.6 Comparing the initial and 2nd water losses

Before

[m3/day]

After

[m3/day]

Increase

/decrease

[%]

Billed metered

consumption

2180.4 2397 + 9.9 Billed

authorized

consumption Billed unmetered

consumption

0 0 0

Unbilled metered

Consumption

413 413 0

Authorized

consumption

Unbilled

authorized

consumption Unbilled unmetered

consumption

0 0 0

Unauthorized

consumption

0 0 0 Commercial

losses

Metering inaccuracies

and data handling errors

122.7 116.4 - 5.2

System

input

volume

Water losses

Physical losses 518.9 308.6 - 40.5

Conclusion

The block system is considered in water networks as an effective approach for reducing water losses. Together, two strategies are applied: checking metering devices to reduce the commercial losses and a series of tests to reduce physical losses. In this study, we select an area to test this approach as a means for controlling and managing leakage in anticipation of extending it to the entire City of Busan. For this test, we ignore billed unmetered consumption and unbilled unmetered consumption because these values are very small comparing with others. Also, unauthorized ones are assumed zero

From the test results, it is found that the commercial losses reduces from 122.7m3/day to 116.4 and the physical losses considerably decreases up to 40.5%. Total reduction of water losses in the project area is 216.6m3/day (i.e. 33.8% of initial water losses) and the City is able to save about US $ 395,000 per year only in the 2nd block. Now the City encouraged by this result is positively considering of conducting the approach to the entire city networks for leakage management



References C.T.C. Arsene et al.(2002) Modelling and simulation of water systems based on loop equations. I.J. of

Simulation 5(1/2), 61-72 Gofman E. et al.(1982) Loop equations with unknown pipe characteristics, J. Hydraulics Div 109(9/12), 1047-

1060 B. Ulanicki et al.(2000) Open and closed loop pressure control for leakage reduction, Urban water (2/12) 105-

114 Germanopoulos et al.(1985) A technical note in the inclusion of pressure dependent demand and leakage

terms in water supply network models Civil Engineering System (2/12) 171-197 Lambert A. et al(1998) Managing water leakage economic and technical issues. London, UK: Finalcial Times

Energy May J.(1994) Pressure-depended leakage, World Water and Environmental Engineering Magazine, 17(5/12) Nielsen H. B. et al(1989) Methods for analysing pipe networks, J. Hydr. Engrg., 115(2/12) 115-157

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