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Trang 1THE FOLLOWING CAN BE USED AS A GUIDE TO ESTIMATE PIPE FRICTION LOSSES AND MAXIMUM PRESSURES FOR PRESSURE FLOW IN PLASTIC PIPE
FRICTION LOSS AND PRESSURE CALCULATOR
Notes
5 L/s
50 mm refer to Table 2 for metric pipe and Table 3 for rural pipe sizes for typical diameters ranges and pressure ratings
10 m straight length not including fittings
Equivalent length of fittings 2.00 m use calculator attached to Table 1 below to estimate an equivalent straight pipe length for fittings.
Elevation head 3 m difference in level between source water and discharge point
1.44 m to decrease losses use a larger diameter pipe
2.55 m/s recommended maximum pipe velocity is 1.5 m/s, try a larger diameter pipe Maximum pressure head 4.44 m represents the maximum pumping requirements (if applicable) and the maximum pipe pressure Refer to Tables 4 to 6 for maximum allowable heads for different class pipes.
Some general notes to consider:
1 For a given flowrate, a LARGER diameter pipe will have a lower velocity and lower pipe friction loss.
2 For a given flowrate, a SMALLER diameter pipe will have a higher velocity and higher pipe friction loss.
3 Higher velocity in a larger diameter pipe produces less pipe friction loss when compared to the same velocity in a smaller pipe.
4 Higher pipe friction losses require larger pumps or can reduce flows at outlets They can also result in higher power costs to run pumps.
5 Pipe velocities should not exceed 5 m/s, and preferably be less than 1.5 m/s
6 Refer to Tables 4 to 6 below for allowable pressures for different pipe categories, as well as pressure deratings at higher temperatures.
TABLE 1 Approximate Equivalent Lengths for Plastic Pipe Fittings
No of fittings Eq Length
Total Eq Length 11.65 m TABLE 2 METRIC PIPE INFORMATION
Nominal Size
source:
DWLBC, 2006
TABLE 3 RURAL PIPE INFORMATION
Nominal Size
DN
source:
DWLBC, 2006
DERATING FOR RURAL PIPE
Temperature Allowable
Head
o
minimum of 9 years expected for water up to 60oC minimum of 50 years expected for water up to 70oC minimum of 1 year expected for water up to 70oC minimum of 25 years expected for water up to 80oC
minimum of 10 years expected for water up to 90o
C
PN20
Equivalent Length
30D
Wall Thickness
Fitting
350D
20D
CALCULATOR
180D 18D
PN16
15D 100D
Flow velocity
50D
Mean ID
Input
Output
Flow
Internal Pipe dia
Pipe length
Estimated friction loss