Appendix 7: Choosing Pipe in a Closed Diversion System
Once you have determined the water source inlet and measured the static head (vertical change in elevation) from the water source inlet to the turbine, measure the lineal distance for the path that the pipe for the diversion system will follow. You now want to select the optimal pipe diameter for your diversion system. The larger the pipe diameter, the less the friction loss will be. However, larger diameter pipes also cost more. You need to meet the hydro turbines dynamic pressure and flow volume requirements. Beyond that, the optimal pipe diameter is the one that gives you the best cost-benefit ratio the least cost per PSI of dynamic pressure. In the graph below we have provided a simple means of determining which pipe diameter to use, based on static head and flow information. This graph is based on the assumption that your pipeline will have no turns or fittings with a radius greater than 22 degrees, and that its overall length is under 500ft. If you do have additional friction losses from these elements, you will need to size your pipeline larger than what we have recommended here. In this case, we strongly recommend you contact our engineering staff to help you in designing and planning your system. Keep in mind that your flow must be adequate to keep the pipeline full even at low water levels to maintain a closed system and prevent cavitation and turbulence caused by air drawn into the system intake.
1in pipe
225
2in pipe
3in pipe
4in pipe
We recommend 5in diameter pipe We recommend 6in diameter pipe
200
175
Head (feet)
150 125
90 80 70 60 50 40 30 20 15 10 5
We recommend 8in diameter pipe
10in pipe use a diversion channel
1000 1200 1300 1400 1500 100 150 700 750 550 600 650 800 850 900 950 50 300 350 500 200 250
Flow (Gallons/minute)
400
450
1100
Appendix 8: Other Pipeline Friction Losses
Another major cause of head loss is in any fittings you might use. Avoid sharp corners in planning your pipeline, because sharp corners will cause turbulence and hence increase friction. The table below lists friction losses associated with various common plumbing fittings. It shows how many feet of pipeline length the fitting is equivalent to, in terms of friction loss. For example: A T in a 4-inch pipeline represents 22ft of head lost OUCH! Your goal in planning your pipeline is to keep it as straight as possible. Bends and curves should be less than 22 degrees. This is best accomplished with smooth, flexible hose sections making gradual curves where necessary, or by carefully heating and bending straight pipe sections to your needs.
Pipe Diameter 1 1 1 2 2 3 3 4
Tee-Run 1.0 feet 1.4 feet 1.7 feet 2.3 feet 2.7 feet 4.3 feet 5.1 feet 6.3 feet 7.3 feet 8.3 feet
Tee-Branch 4.0 feet 5.0 feet 6.0 feet 7.0 feet 8.0 feet 12.0 feet 15.0 feet 16.0 feet 19.0 feet 22.0 feet
90 Ell 1.5 feet 2.0 feet 2.3 feet 4.0 feet 4.0 feet 6.0 feet 8.0 feet 8.0 feet 10.0 feet 12.0 feet
45 Ell 0.8 feet 1.0 feet 1.4 feet 1.8 feet 2.0 feet 2.5 feet 3.0 feet 4.0 feet 4.5 feet 5.0 feet
Some other sources of potential head loss to be aware of: Trash-rack/screen clogged or poorly designed Pipe inlet clogged inlet or inlet not properly submerged Valves use gate, butterfly, or ball valves only in hydro systems as they allow unobstructed flow when open Size transitions in pipeline diameter, both increase or decrease Poorly sealed joints which allow air to be sucked into the pipeline
