| harry k 2005-09-20, 11:21 pm |
|
metalmorphosis@caverock.net.nz wrote:
> harry k wrote:
>
> For gas free water the limit is aprox 34 ft, yes
>
> However water from a spring will have disolved gas and at noticably
> less than 34 ft the gas will come out, and if the flowrate in the pipe
> is too low a gas pocket will accumulate at the high point of the siphon
> and eventually stop it working.
>
> As far as the dip bit goes, I presume the situation could be likened to
> a pipe starting at say 100 ft altitude, climbing to 120 ft, then going
> into a vally with a base at 1 ft then back up the other side to 90 ft.
> This system would flow ( as long as a gas pocket did not form ). There
> is no limit on how low the low point is beyond the point that the head
> would burst the pipe.
>
> If you put a boost pump at the start of the line, the poster will
> increase the max hight of the line to 34 ft + ( head capacity of pump
> )ft, ie a pump that ill pump that has a 30 ft head would anable you to
> get the line over a 64 ft ridge and back down the other side
I am sure that I have seen articles on aqueduct systems containing both
dips and siphons well over the (less than) 34 ft theoretical. A mind
experiment picturing a pipe up 100 ft and down 150 ft would ISTM make a
siphon. But then would outgassing break the siphon?
I agree with you on the 'dip' bit. It should only depend on elevation
differential between the in and out sides at the top. As long as the
out is less than the in it should run all day no matter how deep the
dip. I did find one source (lost it) in google of an aqueduct passing
under a railroad with max dip of 40 ft. Stated that it lost about 2psi
across it. Picture appeared to be about same elevation both ends.
Harry K
|