pvc pipe 2

[cvg]

I'm looking for a good reference for the use of a "n" value of 0.010 or 0.011 for PVC. Client standard is minimum of 0.014.

 

[tincan]

Try the "Handbook of PVC Pipe". You should be able to obtain a copy from your pipe supplier. If not,
Uni-Bell PVC Pipe Association
2655 Villa Creek Drive, Suite 115
Dallas, Texas 75234
I don't have the dot address, might try "PVC Pipe"
Best Tincan

 

[bank]

The "n" value for water/storm service is typically around 0.011; 0.010 is very ambitious and is probably good for brand new pipe only. You need to specify the usage of the pipe also. The City of Houston requires an "n" value of 0.013 for pvc pipes carrying sanitary sewage, which is in the ball park of the 0.014 your client specified.

 

[SlideRuleEra]

While working on a pipeline design years ago came across what sounds like a "real" reason for the various friction factors:
Laboratory testing of an individual length of pipe could very well produce an "n" value of maybe 0.010 or 0.011. However pipelines are not made of one continuous length of pipe, the pipelines have joints. Turbulance at the joints may cause the overall "n" value of an installed pipeline to be about 0.014.

 

[Focht3]

I've looked at quite a few videos of in-place sewer pipe. My money's on [blue]SlideRuleEra[/blue]'s explanation. Misalignment, excess glue, what have you - lots to affect the "real 'n'."

In a (more than slightly) off-topic question, [blue]SlideRuleEra[/blue]: have you ever seen a pocket size cylindrical slide rule? I have an English one - by Otis King (Patent N[sup]o[/sup] 183723.) It has, "B2127 - Made in England" stamped into the bottom. It was a gift - friend went to Great Britain in the early 1980's and brought it back, since I have a small collection of slide rules. Quite unusual -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[SlideRuleEra]

Focht3 - I've seen pictures of cylindrical slide rules, but never the real thing. Sounds like you have quite a collector's item.
Best Wishes

 

[frankism]

Hi, i'm a qaqc inspector with minimal background on mechanical. I would like to ask what is best insulation material for a PVC pipe use in PCW, fiberglass insulation or rubber insulation? How about the polyethylene tape, do we have a specified type for PCW?

 

[91markus]

IIRC, Sverdrup did a study with one of the CIPP contractors a few years ago measuring Manning's "n" values in existing VCT/RCP/PVC pipe before and after lining and two of the predominant factors in affecting Manning's "n" was found to be joints and slime growth.

I believe that PVC that had been in service for a number of years was measured to have values in the 0.014-0.016 range.

Hope this helps.

Regards,
MB

 

[cvg]

was that study for sanitary sewer lines?

My application is for a storm drain line in arid climate. I see very little chance for slime to accumulate in my application. It will be strictly clear water with possibly some suspended fine sediment on an occasional basis.

 

[91markus]

Although I cannot be certain, I do believe the Sverdrup study was in fact done on a sanitary sewer basin (I think it was in Nashville - ealry to mid '90's).

However, as was eluded to in earlier posts, the jointing does in fact cause significant reduction in the "true" Manning's "n" when looking at it from a MH to MH basis.

During my days as a basin drainage modeler (we were using 386's and 486's in those days), most of the models that we set-up and calibrated found that both storm and sanitary were virtually identical in the Manning's "n" values, and 0.014 to 0.016 for older PVC pipe were fairly typical.

Hope this helps.

MB