Re: Pipe friction

From: <Pankaj>
Date: Thu Aug 04 2005 - 09:10:00 EDT

Robin,

I have seen these pipes and truely speaking these ripples are too smooth to increase friction co-efficient. Best conservative approximation would be to redo the calculation with a reduced pipe inside diameter (Pipe OD - 2* wall thickness at the ripples) for the entire pipelength keeping the same friction factor and compare the results.

If you really wish to calculate the exact friction factor, you have to consult a research laboratory which might not be necessary in your case.

Regards,
Pankaj Mandal.

Robin Badcock <rbadcock@vision.net.au> wrote: Dear group,

We have had new 250 PN 6 UPVC RRJ pipes delivered to site; these pipes have a very ripply finish inside the entire pipe barrel. This is for all pipes (1350m)

Ordinarily, a pipe of this size and construction would attract a Hazen-Williams coefficient of; C-151.(Australian Pump Manufactures Pipe Friction Handbook).

The question has been asked as to what influence the ripply bore may have as to increasing energy losses.The ripples are perhaps more like elongated smooth scales that are overlapping somewhat so as to have a layering effect. They are smooth to touch and are approximately 13mm in length, 10mm in width, and are oval in appearance. The protrusion into the water flow (above what would be considered the normal pipe barrel base line) is in the order of 0 .75-1mm. Hence, from the crest of one scale to the valley of the next adjacent scale is approximately 1mm.

Question: I seek suggestions as to what the new coefficient may be estimated at;

                and I seek suggestions as to where information may be gleaned to

reinforce this information/suggestions.

I have been scouring my hydraulics manuals with some success, although there seems to be more information on all the other Friction Loss Equations that have ever been cooked-up. I guess I could work through some of the other formulas and extrapolate the information across so as to get a rough indication as to the new C value, but hey you Dudes are far smarter than I and I am curious as to what may arrive in my mail box.

Cheers for now and thanks.

Robin

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[Non-text portions of this message have been removed] Received on Thu Aug 04 09:10:00 2005