12 replies to this topic

[baritonomarchetto]

Hi all,

sorry for upping this old post, but i need some indication about pipes roughness.

First of all, my name is Marco, i am graduated in material science (so, i am not an engineer) and i am dealing with anti-corrosion coatings for pipe lines.

My boss asked me to:

- find out some guideline in the selection of the rugosity of pipes to be used in different environments (gas, oil, and so on). I saw that in this topics you refer to some general "common-sense experience- based rules, but i need some Reference/Citation.

- find out the lower roughness commercial pipes can have.

I am in trouble with this points because i have no resources (standards and whatever)... only the net is my resource.

thanx in advance for the help

[Qalander (Chem)]

Dear
I am thankful for you reallization indeed!There should many helping relies coming your way soon.
Best Regards
Qalander

[Rama]

Dear Mr. Marco,

The roughness coefficient referred to in pipeline flow calculations depend upon the material and finish of the pipe and not on the fluid it handles as implied by you. Often the pipes used for the various duties mentioned by you are from the same source.

For flow calculations we use the roughness coefficient in the Manning’s Formula (See
http://www.engineeri...ness-d_799.html ) You could use this as a starting point for your comparison.

Then there is the ‘machining grades’ or ‘surface roughness’ of “Machine Finishes” used in machining work shops. These can even be measured by Surface Roughness Testers (See http://www.portablet...ts.phtml?pid=sr ) You may also look up the Wikipedia entry for “Roughness”

Trust this gives you a starting point for your research.

[katmar]

See

http://www.efunda.co...s/roughness.cfm

This is an alternative approach to that which Rama presented. In addition to the Manning formula there is another popular formula for computing pressure drop. This formula is called the Darcy-Weisbach formula and is more frequently used by chemical and mechanical engineers, while the Manning formula is more popular with civil and sanitation engineers. The efunda data applies to the Darcy-Weisbach formula.

These roughness values relate back to "equvalent sand grain sizes" because the original experiments were done with smooth pipes that were artificially roughened by glueing sand particles to the inner wall. Today roughness values for use in Darcy-Weisbach are back-calculated from pressure drop measurements rather than by direct measurement of the surface roughness.

[ankur2061]

Hi Marco,

I very recently was involved in making a company standard for a very reputed offshore O&G company and I am providing data given in this standard verbatim for your ready reference. The standard has been accepted by the company and formally approved. following is the data:

Pipe roughness

For all calculations of pressure drop, the following pipe roughness values should be
used:

a. Carbon steel (CS) corroded: 0.46 mm (0.018 inch) (Note-1)
b. Carbon steel (CS) non-corroded (for relief system piping): 0.15 mm (0.006 inch)
c. Carbon steel (CS) non-corroded (other systems): 0.046 mm (0.0018 inch)
d. Stainless steel (SS): 0.046 mm (0.0018 inch)
e. Titanium and Cu-Ni: 0.046 mm (0.0018 inch)
f. Glass fiber reinforced polyester (GRP): Vendor to provide
g. Polyethylene, PVC: Vendor to provide
h. Flexible Hose: Vendor to provide

Notes:
1. The value of 0.46 mm (0.018 inch) shall be used when hydraulic calculations are
performed for existing pipe installations including relief piping.

Reference is made to BP GP 44-80 for roughness values for relief system piping.

Alternatively have a look at Norsok standard P-001 "Process Design", Edition 5, September 2006 for pipe roughness guidelines. This standard can be downloaded free from the following web address:

www.standard.no/petroleum

Hope this helps to answer questions regarding pipe roughness.

Regards,
Ankur.

[awesome]

ankur2061:

 

How can I calculate roughness for a pipe internally coated with Concrete?

[S.AHMAD]

Dear katmar

I an sorry I was incidentally or mistakenly click the RED button instead of the GREEN one I do not how to cancel it. I am sorry.

Your comment is a good one.

[katmar]

No problem! My goal in participating in these discussions is to learn and to share where I can - not to win votes. Anyway, I see the kind Administrator has re-instated the vote in case my ego was bruised ;-)

[S.AHMAD]

Thank you Katmar.

My goal is the same as yours. To share and learn from others experience.

Best regards

[kkala]

Dear katmar I an sorry I was incidentally or mistakenly click the RED button instead of the GREEN one I do not how to cancel it. I am sorry. Your comment is a good one.

I think negative feedback to "Chronic" (20 Sep 2011) concerns a similar case, so far untreated. See http://www.cheresour...__fromsearch__1.

[kkala]

1. In literature pipe roughness values (ε) used in Darcy formula are in close agreement to those quoted by Ankur. We observe that ε=0.046 mm for non corroded steel pipe, versus ε=0.46 mm for corroded, which verifies the ten fold increase reported by Coulson - Richardson in "Chemical Engineering". In local applications ε=0.046 mm is generally assumed for steel pipes, without any further margin (for corrosion).
2. Norsok standard P-001, page 9/22, reports in addition ε=0.02 mm for GRP pipes, 0.005 mm for PE or PVC, 0.005 mm for flexible hose of plastic coating and (ID in inches)/20 mm for steel flexible hose, last two values in case of no available data from vendor.
3. Additional data from Perry: Drawn tubing (glass, lead, brass) ε=0.00152 mm, asphalted cast iron 0.122 mm, galvanized iron 0.152 mm, cast iron 0.259 mm, wood stove 0.183 - 0.914 mm, concrete 0.305-3.05 mm, riveted steel 0.914 - 9.14 mm.
4. The most complete collection of surface roughness values found is in "Memento des pertes de charge" by I. E. Idelcik (french language), Eyrolles, Paris, 1969, translated from Russian by Mrs M Meury. Despite my poor French now, attached "roughness.xls" shows some collected values of ε, in comparison to Perry's.

Note: The smaller the pipe diameter the more important the influence of ε. It is also noted that pipes with scales inside have increased roughness compared to same pipes without scales. Even internal diameter can decrease because of the scales.

Attached Files

•  roughness.xls   21KB   343 downloads

[Enginnerd]

Ankur:

Are these Relative or Absolute values?

[ankur2061]

Enginnerd,

Relative roughness is defined as

ε/D where ε is the absolute roughness and D is the pipe diameter. The above values are absolute roughness values.

Regards,
Ankur.