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Sully03 (Civil/Environme)
17 Sep 07 9:56
I trying to locate documents (or opinions), which suggest a maxium velocity for PVC pipe (sanitary sewer) before scouring becomes an issue.
Cory
bimr (Civil/Environme)
17 Sep 07 10:08
Do you mean minimum velocity?
Sully03 (Civil/Environme)
17 Sep 07 10:26
No i mean maximum.
Cory
gerhardl (Mechanical)
17 Sep 07 11:29
I am probably not the right person to give you the answer you are searching. I believe, however, there are some natural limits, and that the pipe supplier would be the right source of information to advice you for waste-water of different mix in different pipelines. 字串6
If pumps are used, pump suppliers would have to be consulted. The pumps probably more sensitive than pipelines (?)
You will however have to give some description and limitations to normal content, flow and load over time. What 'normal' stands for can probably be discussed, but you should try to give an upper and lower limit of all parameters to discuss with the pipe supplier. Some 'lifetime test results' ought to be available, technical data given.
If you are discussing 'parameters above normal', that is something else. Both concrete and chrushed stone are after all transported in pipelines, and the abrasive effect (scouring) and reduced standtime of pipelines with necessity of special pipeline materials are obvious. ..But then you will also need other experts.
jgailla (Geotechnical)
17 Sep 07 12:57
Ten States Recommended Standards for Wastewater Facilities (33.45) says under sanitary sewers: 字串8
"Where velocities are greater than 15 fps, special provisions shall be made to protect against displacement by erosion and impact."
Although we're ususally designing for minimum velocities in sanitary sewers and force mains, I would try to keep maximum design velocity under 8 ft/s if possible.
bimr (Civil/Environme)
17 Sep 07 15:12
"The erosive action of the material suspended in the wastewater depends not only on the velocity at which it is carried along the invert of a sewer but also on its nature. Because this erosive action is the most important factor in determining the safe maximum velocities of wastwater, the character of the suspended material must be considered. In general, maximum mean velocities 2.5 to 3.0 m/s (8 to 10 feet/sec) at the design depth of flow will not damage the sewer."
Wastewater Engineering: Collection and Pumping of Wastewater, Metcalf & Eddy. 字串1
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