Pipeline Roughness 1

[brisbane]

Pipeline internal roughness has a large effect on the pressure drop for a gas pipeline, but the literature has wide variations. 0.020 mm (750 mil) appears to be a good design figure. What figures to others use?
Does regular pigging improve the roughness?

 

[Mark62]

It is to a degree dependent on pipe material and productin methods. For steel line pipe I use an absolute roughness of 0.15mm, for plastic pipe I use a value of 0.0015mm and for flexible pipe with an internal carcass a value of ID(mm)/250

 

[GMMJ]

I measured the roughness of an epoxy-lined pipe sample.
The results of this test showed that the average roughness value for the sample was Ra = 4.4 micro m.

 

[1969grad]

Common practice in gas transmission pipelines is to use a design value of 750 microinches for new, clean, bare steel. Range is considered by most to be 500-750 microinches.

The longer the pipe sets on the ROW then the higher the roughness. For example, roughness after atm exposure of 6 months is 1000-1250 microinches, for 12 months it is 1500 microinches and for 24 months it is 1750-2000. I am sure that salt air would accelerate the above corrosion rates.

As the Reynolds number increases then the pipe roughtness has a less and less impact on the friction factor.

 

[djoseph]

What is the best instrument to measure surface roughness for an internal gas pipe surface?

 

[brisbane]

djoseph, We have to be careful here.
The roughness for pipeline calculations cannot be measured, it is a theorectical roughness that is used in the flow calculations. My further research agrees with 1969grad (I also graduated in 1969) that 1000 microinches or 0.025mm is a good safe design number.