Looped Hydraulic Network System Curve

Engineering software applications assume a basic knowledge which you lack. These programs are meant to speed up repetitive calculations to reduce math errors and so on.

The basics include: Bernoulli equation, Darcy-Weisbach, Moody diagrams. Get a textbook and read it.

Thanks, but no thanks for no help at all.

Anybody else?

I checked your post history and I see that a similar recommendation (to obtain NFPA 14 Standards Handbook) was suggested two years ago in response to a very basic question that you had asked here at that time.

I seems that you have not taken this very sound advice.

There are no shortcuts. A the very minimim, pick up a handbook or go on-line and find some pump curves and study these.

You're still not helping.

The solution is the point of intersection of the pump curve with the system curve.

When you change the pump characteristics, this intersection point will also change, assuming the system remained constant.

ok, but my question was not about the pumps duty point, it was about the construction of the system curve. Normally, in branched networks you combine the branches in parallel to obtain the overall system curve. It is not quite clear to me how to do this in the looped network, as there are pipes in parallel and in series and that makes it confusing. I am actually asking if there is any algorithm to do this easy or I'll need to combine like 100s of serial and parallel pipes to get it?

Hardy-Cross is used to solve pipe networks.

The computer programs are based on Hardy-Cross.

Which brings us to the beginning of this thread i.e. how to utilize results of the analysis in order to construct the system curve?

There will be many system curves in the network, one at each node.

Usually there will be a source or reservoir followed by transmission line from the source to the distribution area. In the dstribution area there will be many pipes in parallel running around the service area. There may also be booster pumps, pressure reducing valves, distribution storage tanks, fire hydrants, water meters, and individual building connections.

Along the transmission line there will be one hydraulic grade line at each point. But after you enter the distribution network, you need to identify which of the many hundreds of "nodes" that you are interested in drawing water out of the network from.

You cannot have one system curve in a distribution network. Pick a node or nodes of interest and after having solved the network by balancing the flows, you may then ask, what pressure drop will I have at node "A" should I require 2k gpm flow while maintaining 20 psi pressure for 15 minutes to fight a fire (for example)?

Obviously more pressure and energy will be available in the lower portions of the grid according to Bernoulli's equation. At the top of the hill there may be no pressure or even a negative pressure during the fire. The city will then burn down.

OK thanks a lot.