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.
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?
