Water flows & pressures in a distribution system 1

[waternewbie]

I just started work as a design engineer for a local water distribution company. What I need is a better understanding of how flows and pressures work within the system and the effect that fittings have on them. Its all pretty new to me and I'm struggling to find any decent literature on the subject. If anyone can be of help I would be eternally grateful!

 

[dicksewerrat]

You should review your textson 'hydraulics. then go tothe piping fitting manuals and handbooks. They have the head losses for all the fittings as a length of pipe. The most important thing to remeber isthat the water is not compressable. You can take out only the same volume you are putting in.

 

[IFletcher]

A good book for fitting losses in large pipe is the Hydraulic's institute Engineering Data book. Another good source with formulas for real world applications is the Crane Flow of Fluids technical paper 410.

 

[KRSServices]

As dicksewer pointed out, I suggest reviewing your hyraulic texts. Next, I would get a water model program (WaterWorks, Watercad), preferably Heastad Watercad, with an existing network say 250 pipes or so with at least two reservoirs/pumps. Next load it up and start to change configurations, add nodes and pipes, play with demands and pipe sizes and simulate flow tests etc. Next if you can, get involved with the local operators and do some flow tests from hydrants, closing faster or slower and observe the flow stream and note upstream/downstream pressures as opposed to the water model. With headloss, compare field results with the model, noting the number of bends, tees, valves, etc., relative to published headloss values. Observe flows and pressures (flow tests) in old cast iron pipe versus newer PVC. Remembering the C value, try to find some old cast or ductile iron pipe and see the scaling on the pipe walls. As an authority, the must be a yard full of the old excavated pipe. Most of all, learn your system relative to a model. KRS Services

http://www.krs-services.com

 

[noahfit]

you can learn the basic from this webpage

http://www.mcnallyinstitute.com/CDweb/cdpage.htm

 

[waterexpert]

Alternatively, go to

http://www.lmnoeng.com/

this has both the theory, as well as free calculation tools you can use to check your answers.

 

[stanier]

Download the freeware Epanet. This will enable you to buildmodels of networks using different pumps and valves etc. You will get a handle on the way things behave. Also get yoru hands on technical Paper 410 by Crane. this is the bible for most things in fluid transport.

Some good stuff on

http://www.pipingdesign.com

Sharing knowledge is a way to immortality

 

[RWF7437]

Another good reference is Roland Jeppson's, Analysis of Flow in Pipe Networks, Ann Arbor Science Library.

Valves and fittings are usually ignored in many analyses and networks are "skeletonized" by leaving out very small pipes to rduce the calculation time with only a small loss in accuracy.

Russ Faust
Salem, OR USA

 

[BobPE]

fittings do not have much affect on healoss overall in the distribution system. Thats why we classify them as minor losses.

BobPE

 

[waterexpert]

Remember that the previous two posts only hold true for the distribution system. At the higher line velocities you are likely to encounter within a treatment works, fittings losses can be far more significant than straight run losses.
Fittings headlosses go up with the square of line velocity.