Re: Pipe friction

From: <Christopher>
Date: Thu Aug 04 2005 - 11:48:00 EDT

On Aug 4, 2005, at 8:10 AM, Pankaj Mandal wrote:

> 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.

Or adjust the hydraulic diameter (=4(cross-sectional area)/(wetted perimeter)) to include the actual geometry. Unless the fabrication is really squirrelly it won't make any practical difference. The data used to generate friction coefficients scatters all over the place, and your correction will probably fall inside the scatter band anyway.

If the 'ripples' are big enough to affect the hydraulics, they're probably big enough to affect the structural response. Make sure that the pipe dimensions comply with the requirements of your specific piping code and the applicable ASTM spec. You may not have a problem with everything new and uncorroded, but pipe never improves with time or repairs itself or gets accustomed to overload. Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=SBKolHRwRlqINupT4ouEUNk36hW1f0xchu_0ELdiWv8mOqcLer6YktsT8Z7FND21Nxs4tfc0obvs5fI">chrisw@skypoint.com</a> | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a> Received on Thu Aug 04 11:48:00 2005