One important thing to consider is that every time the pump starts with this scenario it will be pumping into an emptied line. The pump will run down its curve and may trip on overload if the motor is not sized for all points on the curve. This will send a slug of water to the end of the line causing even greatyer transient surges. A hydraulic control valve at the end of the line could be used to keep a minimum pressure in the line to keep it full. The pressure would be equal to the static head of the system.
If air valves are to be used those with multiple orifices such as Ventomat ofr
Glenfield should be the first choice.
--- Gang Cvg <cvg_gang@yahoo.com> wrote:
<HR>
<html><body>
<tt>
Dear David,<BR>
As you have been warned about the possible vacuum<BR>
formation, which seems to be quite genuine, I think<BR>
you have to look for some solution of istalling an (or<BR>
more in number with stand-by philosophy) automatic<BR>
vacuum breaking valve similar to the ones used on tank<BR>
tops.<BR>
In the event of building up of such a vacuum, it will<BR>
open up and let in the atmospheric air to fill the<BR>
space emptied by the receding water. During its normal<BR>
intended duty it wil close the port to prevent any<BR>
loss of water to the atmosphere. Keep the stand-by one<BR>
always well tuned. Please give a thought to it. You<BR>
might get still better solutions. Good luck!!<BR>
C. V. Gangadharan.<BR>
--- Wilkonet <wilkonet@yahoo.com> wrote:<BR>
> Hi Everyone,<BR>
> <BR>
> I've recently started my first main job as a trainee<BR>
> mechanical <BR>
> engineer. One of the first problems ive came across<BR>
> is to modify a <BR>
> piping system for supply water to a power plant. The<BR>
> material is <BR>
> hdpe, 450mm dia, 7400m long. The is currently<BR>
> insufficient flow so a <BR>
> modification is needed. My modification means that<BR>
> the change in <BR>
> elevation from pump to dam is now -8m instead of<BR>
> previously 8m. (the <BR>
> pipe would be re ruited)This in theory would give<BR>
> suffiecent flow. <BR>
> However I have been warned that if the pump is<BR>
> turned off this could <BR>
> cause a vaccuum to be formed and the pipeline to be<BR>
> crushed.<BR>
> <BR>
> I have been searching through the net to try and<BR>
> find some <BR>
> information on designing pipe systems but have<BR>
> failed to find <BR>
> anything to give me information on a system which<BR>
> pumps 'down hill'.<BR>
> <BR>
> It would be great if anybody could give me some<BR>
> advice or any <BR>
> information which would halp me in my problem.<BR>
> <BR>
> Regards,<BR>
> <BR>
> David Wilkinson<BR>
> <BR>
> <BR>
<BR>
<BR>
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ask is for referrals for designs they help with.<BR>
877-610-8924.<BR>
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