1.0INTRODUCTION
1.1Background
DZA Consult Sdn Bhd has been commissioned by Perbadanan Kemajuan Negeri Selangor (PKNS) to provide Civil & Structure Consulting Services for the proposed development.
The proposed tapping of water supply shall be tapped from SYABAS’s existing main pipe of the 525mm diameter with available residual head 68.83m ODL at Pesiaran Keruing (Persiaran Zurah 1). The main pipe location was shown in the layout plan to the pipe reticulation network system.
1.2Purpose of Report
This report is to describe in detail the design concepts and to seek the approval from Syarikat Bekalan Air Selangor Sdn. Bhd. (SYABAS).
2.0DESIGN CRITERIA
2.1 Design Flow
The following design criteria are used to check and design the water supplysystem . The reticulation shall be consider for two (2) conditions:
i)Peak daily demand = 2.5 x average daily demand (case 1)
iii)Average daily demand + fire flow (case2).
where peak flow = 2.5
2.2Fire Flow
The following flows discharging concurrently shall be assumed for fire flow analysis:
Four (4) hydrant discharging 1370 lpm (22.8 lps) each shall be assumed for fire flow analysis
2.3Pipe Losses
Head losses of pipes are computed using Hazen Williams formula :
H= 15 L (Q)1.85
D 4.87 (C)1.85
where, H = head losses in ft.
L = length of pipe in ft.
Q = flow in gpm
D = pipe diameter in inch
C = Hazen Williams pipe constant
Note: i) Value of C is taken as 100
ii) Minor losses neglected due to conservative value of C
Maximum head loss not to exceed 2m per km for daily peak flow
2.4 Residual head
A minimum residual head of 7.5m (25 ft.) shall be taken in the design
2.5 Pipe lines
i)Pipe Material
a)The water mains shall be Ductile Iron pipes.
b)All pipes and fittings shall comply with the current Malaysian Standards, or equivalent.
ii)Valves
a)Air valves shall be provided at peak points
b)Adequate in line valves shall be provided to isolate sections of the mains to facilitates maintenance.
c)Adequate scour points shall be provided.
d)Approved SYABAS, type precast valve chambers shall be used.
e)All valves shall comply with the current Malaysian Standards or equivalent.
iii)Pipe Cover
a) Minimum cover to pipes shall be 900mm generally and if this is not practical, steel pipes shall be used.
b)Minimum cover to pipes laid under paved areas shall be 1200mm.
iv) Anchor/Thrust Blocks
Anchor/Thrust Blocks shall be provided at all bends, tees and “stop ends” and designed to withstand full test pressure.
3.0TOTAL WATER DEMAND
3.1The total demand for the project is as follows:-
Type of Building / Water Demand (gal per day)Lot Perindustrian (1 unit) / 700
Therefore, Total Water Demand For 10 unit Lot Perindustrian (Kilang) / 700 x 10 unit
= 7,000
4.0INCOMING SYABAS MAIN PIPE FOR WATER SUPPLY TO WHOLE DEVELOPMENT
The proposed tapping of water supply shall be tapped from SYABAS’s existing main pipe of the 525mm diameter with available residual head 68.83m ODL at Pesiaran Keruing (Persiaran Zurah 1). Refer letter from SYABAS HULU SELANGOR: SYA/HS/TED/PDS/PJT3/RD1447/12(1) dated 05 Oktober 2012.
Total consumption for the development = 7,000 gpd
= 292 gph
Flowrate factor for incoming main = 2.5
Therefore, the design flow rate = 2.5 x 292 gph
= 730 gph
Minimum velocity = 3 ft. per second for pipe diameter for incoming main < 300 mm diamater (12’ dia).
To determine the diameter for incoming main pipe:
Q= VA
Q=730 gal x 1hr x 0.16 ft3 = 0.032 ft3/sec
1 hr 3600 sec 1 gal
A=Q=0.032 ft3/sec = 0.011 ft2
V 3 ft/sec
A = 0.011 ft2
A = D 2 = 0.011 ft2
4
D = 0.12 ft x 12 in x 25.4 mm
1 ft 1 in
= 37 mm
Therefore, adopt 150mm dia.DI Pipe
5.0Residual Pressure Head
Estimated length of incoming main pipe = 350 m
To incorporate effects of main losses, the pipe length is increased by 2%,
Length = 350 m + (2% x 350 m) = 357 m
Total head loss , HL = 357 x 2
1000
HL = 7.14 m
Proposed Highest Supply Level, HSL = 45.73m ODL
The minimum residual head required by SYABAS is 7.5m (25ft.)
Residual pressure head available = TH – H - HL
= (68.83 – 45.73 – 7.14)m
= 15.96 m > 7.5m (25ft.) … OK
Therefore, pump system are not needed.
6.0 RESULT OF NETWORK ANALYSIS
6.1 The result of the analyses are indicated in Appendix 2 for peak flow
and average and fire flow respectively and summarized below.
6.2 Peak flow : From Appendix 2, the lowest residual head is 23.77m at node 4, 5 & 6.The residual head at all nodes are sufficient to provide the minimum required head of 7.5m (25 ft.).
6.3 Average flow and fire flow : From the Appendix 2, all residual head at the node are above the minimum requirement of 7.5m (25 ft.). The lowest residual head is at node 5 with 25.01m.
7.0CONCLUSION
From the analysis, the proposed pipe distribution network system satisfied both the requirements for peak domestic draw off and fire flows. Hence, the proposed pipe distribution network system is adopted.