INTRODUCTION AND NOTES ON USE
This model derives the total net present cost of 5 pipeline and pump scenarios. Included in the analysis are capital and running costs.
Inputs include : Flow, pipeline length, static head, pump duty and efficiency, power costs, project life and discount rate, water temperature pipe DN and pipe bore roughness.
Abbreviations: The following abbreviations have been used
1) Pipe type
| 1. TYTONXCEL |
...XL |
| 2. TYTONXTREME |
...XT |
| 3. TYTONXTEND |
...XN |
| 4. Classic K9 |
...K9 |
| 5. Classic K12 |
...K12 |
2) Lining type
| 1. Ordinary Portland cement mortar (OPC) |
...C |
| 2. OPC plus seal coat |
...CSC |
| 3. Calcium aluminate cement mortar |
...CA |
| 4. Unlined |
...U |
Outputs include: assessment of pressure class required, maximum velocity, total installed cost, net present value of operating cost and total net present value for each option. The optimum DN can then be chosen as the minimum NPV.
NOTES ON DERIVATION
Energy Costs for NPV analysis
Pumping power
P = Power in Joules per second, or Watts
Q = Flow in cumecs or m3/s
r = Density of water normally taken as 1000 kg/m3
h = Total pumping head including friction and static head both in metres
h = Pump efficiency normally taken as 70% ie 0.7
Pumping costs
A = Annual pumping costs in $
h = Pumping hours per day
P = Pumping power in kilowatts
c = Power cost per kWh
Pump station capital cost assumptions
Power, kW
100
100 < P< 500
>=500
Pumping power requirements
P = pumping power in kW
Q = flow in l/s
H = total pumping head in metres
E = pump and motor efficiency in %
Annual power cost
A = annual power cost in $
d = pumping duty days per annum
h = pumping hours per day
P = pumping power in kW
c = power cost per kWh in cents
DCF factor or net present value of an annuity
DCF = ( 1 - ( 1 + r ) -n ) / r
DCF = discounted cash flow factor
r = discount rate %
n = term of operation in years
Hydraulic flow calculation by the Swamee-Jain formula
s = 0.203 Q 2 / ( g D5 ) / ( log ( k / ( 3.7 D ) + 5.74 / ( R 0.9 ) )2 )
s = hydraulic gradient in m/m
Q = flow in m³/s
g = gravitational acceleration in m/s/s
D = internal pipe diameter in m
k = equivalent sand grain roughness in m
R = Reynolds number = v D / n
Default installation costs
The following table represents a rough estimation of the ratio of installation cost to pipe purchase price, as a function of diameter. Installation cost = M x pipe purchase price
DN
100
150
200
225
250
300
375
450
500
600
750
M Factor
3.0
2.5
2.5
2.5
2.0
2.0
1.5
1.3
1.0
0.8
0.6
Maximum allowable operating pressure (MAOP)
AOP = Allowable operating pressure =
PN/10 MPa
AOP = 2Rma/(Y-a)
Rm = design hoop stress = 420/3 = 140MPa
a = minimum wall thickness in mm
Y = mean outside diameter in mm
