Flexible pipe roughness
Flexible pipe roughness
(OP)
Hello everyone,
How can I compute approximately the flexible pipe head loss?
I read in this forum that I should be using a roughness of ID(mm)/250 but how can I use this to have the pressure drop.
thank you
How can I compute approximately the flexible pipe head loss?
I read in this forum that I should be using a roughness of ID(mm)/250 but how can I use this to have the pressure drop.
thank you





RE: Flexible pipe roughness
http:
RE: Flexible pipe roughness
RE: Flexible pipe roughness
However, for me, the issue is that you use a ID-dependent absolute roughness that begets a ID-independent relative roughness since in Moody diagram, we use the e/D relative roughness.
For example,
You have a flexible pipe with ID=8"
The absolute roughness is e=ID/250
To use Moody you will have to get the relative roughness defined by e/D with D=ID so the relative roughness is 1/250 whatever the inner diameter of the flexible pipe ...
You could say that in this theory a pipe with ID=6" is equivalent to a pipe with 8" etc..
RE: Flexible pipe roughness
RE: Flexible pipe roughness
The danger here is that you could underestimate the pressure drop and find yourself with an undersized pipe...
RE: Flexible pipe roughness
e = absolute hose roughness
D = ID
RE: Flexible pipe roughness
Like I said and like you said, the relative roughness pipe is e/D with e = absolute roughness (in the case of flexible pipe it's apparently ID/250 see: Mark62 http://www
and d=ID
so relative roughness is equal to (ID/250)/ID = 1/250 which means that whatever the ID , darcy friction factor is independent of your geometry...
I find it surprising, that's all .
I'm not asking about calculating pressure drop in general but only about the relevance of this formula (e=ID/250) !!
RE: Flexible pipe roughness
absolute roughness = 1/250 = 0.004
then,
rel roughness = 0.004 / ID
but I'm guessing there.
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso
RE: Flexible pipe roughness
RE: Flexible pipe roughness
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso
RE: Flexible pipe roughness
What do you mean by i-one ? ID-1?
To ione thanks for your answer, I guess now you understand what my problem is... I am in front of a formula that I must use while I know it's irrelevant.
Maybe someone could enlighten me on how Pressure drop is assessed in a flexible pipe like NKT's flexible pipe . What darcy friction factor to use to take into account the carcass geometry.
RE: Flexible pipe roughness
http://www.gates.com/index.cfm?location_id=3042
RE: Flexible pipe roughness
Is it a flexible pipe, is it a flexible hose, how does it calculate those results ?
RE: Flexible pipe roughness
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Flexible pipe roughness
RE: Flexible pipe roughness
I am talking of a flexible pipe used in the subsea oil and gas industry like this one http://www
The carcass profile is the problematic geometry here. I wanted to know if there is another way of calculating flexible pipe pressure drop than using an absolute roughness of ID/250 since like I said this leads to an ID-independent darcy friction factor.
In the link provided by SToneCold (thx btw), it seems a similar formula is used, i.e a formula that leads to an ID-independent darcy friction factor.
RE: Flexible pipe roughness
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Flexible pipe roughness
The closest geometry being the corrugated pipe, it seems corrugated pipe correlations should be used instead ...
So nobody can explain why the formula e=ID/250 for a flexible pipe is used?
(http://www
RE: Flexible pipe roughness
However I'm sure that it wouldn't be the first time that an error was propagated time and time again, especially across the internet.
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso