roughness data for pipe

[Pipeline1972]

hello everyone,
i'm working on a list of pipe materials for which i need to find the roughness values, for use in a pressure loss calculator.
I've done quite some research, including here, and i was surprised to see that:
A. It's hard to find that kind of info
B. Values are different, depending on the source

For example, in the Toolbox, I found a value for stainless steel to be 6E-4 inch, another source tells me 1.8E-3.
For PVC, i found a value of 84E-5. A supplier's source gives me 7E-5.

Anyway, I'm hoping someone could help me out finishing my list by providing me with the Ra values for (or a link to a good source):
Galvanized steel
Zinc plated steel
Cupper

And, I also have a bunch of plastic lined steel pipes. Is it correct to assume the values for the plastic to be used in the case of lined pipes?

Thanks a lot for your insights!

Process - Piping
ing - EiT

 

[MechEng2005]

For you PVC numbers... 84E-5/7E-5 = 12 >> Check units. Possibly different between feet and inches.

My fluids books lists the equivilent roughness for new galvanized iron at 0.0005 feet. Don't know if that's helpful or just another data point that may be different than others you will find.

Book is "Fundamentals of Fluid Mechanics" by Munson, Young, Okiishi.

-- MechEng2005

 

[iken]

I think you will always get different values for roughness, depending on where you look. The best option would be consistant in the values you use (all from one text ref) and make a note somewhere in your spftwarre/spreedsheet that that is whee your values come from.

 

[JohnGP]

From Crane - Flow of Fluids through Valves, Fittings, and Pipe - galvanized iron has roughness 0.12mm (0.0047in) and drawn tubing (copper pipe) 0.0015mm (0.000059in).

For SS, I usually use the same as commercial steel - from Crane that is .05mm (.002in), which is close enough to the 1.8E-3 quoted above. Zinc plated steel is probably close enough to commercial steel also.

Cheers,
John

 

[racookpe1978]

New pipes can come from the references - even though they may differ.

What about dirty, corroded, eroded pipes? That will be "normal service" conditions after only a few months though, right?

 

[Pipeline1972]

ok 1.8E-3 for ss. I'll use that one. The value i found in the engineering toolbox got me confused.

Can we assume the value for galvanized iron to be close enough to that for galvanized steel?

@racookpe:
ours are pipes to be used in clean environment (semicon, photovoltaic). They're not supposed to get dirty.

Process - Piping
ing - EiT

 

[sheiko]

Hope this help.

"We don't believe things because they are true, things are true because we believe them."

 

[JohnGP]

Yes, I would use the value for galvanized iron for galvanized steel.

 

[Pipeline1972]

oops, epsilon for galva iron is .15 mm, not .12

Process - Piping
ing - EiT