RDA 401T Reticulation Design and Management

Tshwane University of Technology
Department of Civil Engineering
RDA 401T: Reticulation Design and Management

Assignment

Question

Fig. 1 shows the plan view of the water transmission pipeline and the distribution network supplying town X. The present population of the town is 24 850 persons with an average growth rate of 2.2% p.a.

RDA 401T Reticulation Design and Management Image 1

Additional information is given in Table 1.

Table 1

Treatment Plant / Pumping Station (TP/PS)

Reservoir

N

Suburbs

1

2

3

4

Horizontal distance from river (km)

0.4

10

12

13

15

16

12

Total head (msl)

1025

1560

Elevation (msl)

1350

1370

1320

1340

1350

The average daily per capita consumption is 100 1 with an hourly peak factor of 2.4. A firefighting demand of 1 rn3 /min is required and the minimum allowable pressure at any suburb is 10 mwc. For a design horizon of 25 years and using the flow nomogram attached,

  1. Design the pipelines from the treatment plant to the distribution reservoir ii. from the distribution reservoir to node N
  2. Determine the minimum acceptable pressure at node N
  3. What is the minimum required power of the pumps to be placed at TP/PS if the available pumps have an efficiency of 69%
  4. The details for loop 1-2-3-4-N are as shown in Table 2. All the pipes in the loop have a diameter of 150 mm. Use the Hardy-Cross method of balancing heads to determine the flows in the individual pipes of the loop. You should carry out a minimum of four iterations. Note that Q is the design discharge from the reservoir.

Table 2

Draw-offs

Pipe

Length (km)

Node 1 = 0 2Q

N 1

1.2

Node O.IQ

1 - 2

2.1

Node 3 = 0 4Q

2 - 3

3.2

Node 4 = O.3Q

3 - 4

4.1

1.1

Nomogram

RDA 401T Reticulation Design and Management Image 2