Roughness of cement lined ductile iron pipe 1

[DPAJR]

Does anyone have a reference for the roughness of cement lined ductile iron pipe? My hydraulics book shows roughness for various types of pipe including ductile iron but it does not specifically say cement lined. An engineer at a water district said he thought it was about the same as PVC but that just sounds way too smooth.

Thanks,
DPAJR

 

[RWF7437]

Try Googling DIPRA

 

[BigInch]

I've not used cement lined pipe, so I don't know. If you have some around, you could you measure it.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[katmar]

The value I use is 0.1 mm for a spun cement lining. Unfortunately I did not make a note of where I got that info - it is just a note in my file that I made at some stage.

It sounds reasonable to me. Other "cement" related info I have is "smoothed concrete" at 0.5 mm and "asbestos cement" at 0.05 mm.

For rigid PVC piping I would use a value of 0.005 mm, so I would agree with you that your colleague is being a bit optimistic.

regards
Harvey

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[cvg]

I typically use a value of C=120 for design of DIP for water supply. New pipe may be closer to 130 but 120 is a conservative number.

 

[blueoak]

My American Ductile Iron Pipe manual suggests a Hazen Williams c of 140 to 150 or higher for high speed cement lining or large pipe sizes. I would use 120 for older existing pipes as cvg suggests for long term or sensitivity analysis. Same as PVC depending on your connections.

Does anyone know of problems with the cement lining in situations where you have 15 fps? The situation has no possible surge (partial pipe flow with no valves) and there are no pumping costs.

 

[stanier]

Roughness when new is .010mm. However deepending on service this can increase to as much as 3mm. Also slimes build up will decrease the diameter and this will have a more drammatic effect on the fluid flow. Unless the fluid is particulalry agressive then a roughness of 0.30mm could be used for a fifty year life.

Use of Hazen Williams is considered to be less accurate than Darcy Weisbach especially in larger sizes.

Was this is in the water distribution forum I take it that the fluid is water and not sewage or a slurry. The velocity of 15fps is only a problem if you have a long line . The head loss will result in high energy costs. Gravity lines often flow at velocities much higher than this figure.



Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[rconner]

It is probable your colleague is essentially right -- I think most contemporary ductile pipe cement mortar linings are from a hydraulic perspective rather smooth, as the centrifugation of the applied lining can make the flow path reasonably consistent in all directions and the lining in addition maintains flow properties in even some quite aggressive water services for a very long time (by not fostering significant growth of tuberculation as was encountered in unlined pipes in aggressive exposure). Also, it should perhaps be emphasized that actual hydraulic performance of pipelines is probably dependent on more than hype/perception or manufacturer’s claims, or even smoothness to the touch of a localized area of e.g. plastic piping material. e.g. the actual flow areas of the same nominal size of different material types of AWWA pipes is commonly not the same. The internal diameter of most common (minimum in small sized pipes) Pressure Class 350 ductile iron pipe is larger than the internal diameter of most commonly specified pvc and hdpe pipes, per the respective, comparative AWWA standards. Actual pipe flow area has of course much influence on hydraulic performance per virtually all formulae approaches. While most solid wall plastic pipes are rather smooth on the outside, some experts have apparently also noticed that at least some plastic pipes have “waves” or undulations on the inside and of course are more subject to long-term ring deflections that apparently can arguably at least to some extent affect hydraulic performance (see e.g.comparative data in the “C.Tables” from e.g. Haestad/Bentley’s “Advanced Water Distribution Modeling and Management”, at

http://www.haestad.com/library/books/awdm/online/wwhelp/wwhimpl/java/html/wwhelp.htm).

I believe additionally some P.E.'s with DIPRA (dipra.org) have worked with some interested actual utilities to run sort of comparative side-by-side flow testing/comparisons of actual working ductile iron vs plastic pipelines in their systems, and they may have some reports available of these tests.

 

[stanier]

rconner is correct. Diameter is more significant than roughness in hydraulic calculations. Although he is part of the ductile pipe industry, he does provide technical correct information.

The tolerance on cement linings is as great as the wall thickness tolerance in plastic pipe wall thicknesses. The difference is the cost of the material. The plastic material costs far more than the cement lining. Hence plastic manufacturers use every device available to manufacture to the tightest tolerance, ie thinnest wall. They make money by selling you the least amount of product that meets specification.

Whereas the cement is a very minor part of the cost of DICL pipe. It doesnt require energy to melt it as does the DI. So manufacturers of DICL put all their effort into the DI side of things.

Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[Gaylon]

We commonly use cement lined ductile iron underground private fire service mains in the fire spinkler industry.
My ref book "The Hydraulics Handbook" published by the Nat'l Fire Sprinkler Assn use a C factor of 140 (Hazen-Williams formula).

Also, reference NFPA 13 Instlln of Spklr Systems, by Natl Fire Protn Assn, which in table 14.4.4.5 states the Hazen-Williams C-factor as 140.