I'm not an expert on fluid dynamics at all, just read this question and this vague idea popped up in my head: Would it also be possible to explain the results with a structuring of the inner wall surface?

Something similar to shark skin that can reduce friction in turbulent flow? http://rsta.royalsocietypublishing.org/content/368/1929/4775.full

I'd investigate the formation/destruction of oxide layers.

Thanks Matthias Arras. But the shark-skin case talks of semi rigid surfaces(fat layer) that acts as dampers & prevent the flow over the sharks' skin from becoming turbulent.

This seems relevant with crude oil pipelines, where wax deposits may serve the same purpose as above.

But my case involves Product(Diesel, Kerosene, petrol etc.) that are completely wax-free.

Thanks Giuseppe Pintaude for your kind considerartion.

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There are several problems in this publication. First and most significant was not evaluated diameter variation before and after Pigging. Simply because the flow loss in the transition zone of the Moody diagram is much more sensitive to changes in diameter caused by the removal of incrustations of the possible variation in surface roughness.

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Perhaps what the manuals Hydraulics and Fluid Mechanics books of the present day does not make a sensitivity analysis for each parameter in the loss of energy.

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I'll make a few calculations with the job data to demonstrate what must have happened.

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kinem. visc = 0.000002 m² / s, Q = 0.07917 m³ / s,

Diam = 0.3000 m, rug1 = 0.0003 m, (Del h) / L = 4.533 km / m

Diam = 0.3000 m, rug2 = 0.00015m, (Del h) / L = 4.079 km / m

Diam = 0.3063 m, rug2 = 0.0003m, (Del h) / L = 4.079 km / m

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Ie, in the process Pigging what happens is the removal of incrustations and not straightening the conduit. If the incrustations is too large, there will also be a decrease in roughness, but what can not be said that the equation performance the Pigging is correct!

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In calculating a decrease by 50% the roughness corresponds to a decrease of 6.3 mm in diameter of a pipe of 300mm, ie 2.1%.

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Importantly, the loss due to the variation of the roughness is represented by a power law with a fractional exponent of 0.5 while the variation of the loss due to the variation of the diameter function is a power law with exponent of fractional order 5! It is a relationship of sensitivity of 1000/1!

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I do not understand some of the other answers, they go off in a tangent.

The pipe when new was most likely made from sheet steel. somewhere say 175 to 275 microinches roughness, - welded into the round pipe longitudinally or helical.

the brushing may have polished the steel - quickly passing a brush over a sheet of steel 200 times - try it. would not change the roughness, it is not so easy.

my guess is the accuracy of the measurement teqhniques P,T, viscosity, volume measurement mass measurement, power measurement, ) has increased.

additionally the fluid has sand ( or silica type dust) in it, which may polish the pipe wall. 60 years would do it.

The composition of the fluid over time may have changed, or the coating on the pipe wall may have changed as well.

an uncertainy analysis is required to identify those parameters that are and are not contributing in a meaningful fashion.

Thanks Rogerio Maestri & Blaine Sawchuk for your kind reviews.

Rogerio: I would like to tell that there is not significant change in Pipeline diameter in this case, because the dirty product that we receive with the inserted PIG is in very small quantity that if supposed to have been uniformly coated on the surface of 200 km pipe length, would mean a decrease in dia. of the order of a few microns.

Blaine: I believe the measurement needs refinement. because the subsoil temp. would definitely not be constant throughout 200 km stretch & thus variation of viscosity/density may also be significant. But my basic question was that CAN A MATERIAL OF LESSER HARDNESS(MILD STEEL WIRES) DECREASE THE ROUGHNESS OF A HARDER MATERIAL(STEEL PIPE) SO MUCH SO THAT IT BECOMES SMOOTH? However, your reason of EROSION by silica particles(that although are supposed to be in the fluids in traces) is well taken.

thanks gentlemen for your contributions

Mohd.

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With the data presented, 200 km of canal, two measures of pressure along the 200 km, different flow rates before and after passage of the PIG, with different Significant figures in the input data (without showing the accuracy and precision in measurements), do conclusions from a single factor, roughness, seems a little out of control testing. One thing is to have operational data in an industrial installation, another thing is to make scientific hypotheses with these data.

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To give an example, an assumption is made that the amount of material deposited along the walls is homogeneously distributed not only along the diameter, but also as over 200 km length of conduit. Do not include the hypothesis that there is singular points in the 200 km pipeline singular points that concentrate the losses due to deposits of material, for this to happen the conduit should be straight and with constant slope with no high or low. Unless we have more data on the course think only assign a homogeneous roughness and perfectly distributed over 200 km is a highly reckless hypothesis.

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I know I'm being very academic in my observations, but one thing is to present an operating measurement result that serves the industry and another thing to make a scientific publication with the same.

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As the formula for the proportional gain efficiency epsilon / Diameter, continue to insist, is incorrect, because putting two independent parameters that act differently in the same equation and not also consider other important parameters in the reduction or increase in loss (do not forget we are not in a fully rough turbulent regime) does not satisfy a clear scientific formulation.

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What could be done to give better credibility to the work is to present the "roughness" calculated before and after passage of the PIG at least would have a view of the variation of this parameter over time.

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Aria.

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The text that you mean, clearly shows that the practical experience of large pipelines of the effects of inclination is to focus areas of accumulation of other fluids (or solids) generating points of corrosion and deposition or concentrated. p227-231

Rogerio Mastri: thank u for enriching the discussion with your inputs. Actually I am not working in R&D feild. I started with correcting the wrong methodology of comparing the flow rate per unit differential pressure across the whole pipelength that is prevalent in some Oil companies...then I got a reference from Schaum's series publication on pipeline hydraulics where a table is given that suggests that roughness of old pipe increases with time....

then, in fact, assuming that the deposits are in the form of minute, discontinuous( presuming a uniform pattern) peaks , I inferred that these deposits (that are generated between subsequent PIGGING) should be similar to the artificially generated roughness that formed the basis of development of MOODY'S CHART, and so I used the chart for calculating relative roughness.....

After your comments, I think I should have used the COLEBROOK EQUATION instead.

further, i request u to please see my full paper.....

Also, for your information, i wud like to share the fact that apart from salt/oxide deposits, colonies of bacteria have also been reported that cause corrosion..

your suggestion of proper measurement of parameters is well taken. actually i m in the engineering deptt not in R&D, thus i don't have access to laboratory...

thank you very much Aria Tsam :)

Ah. very good.

let me query my associates at TCPL and Enbridge who are not members of this forum. To see if they would answer your question as they have been dealing with this topic for years.

thank u Blaine Sawchuk :)

Mohd

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In the nineteenth century, the majority of scientific and technical results came from people who worked in the production and not the academy (equations that have lasted to this day), nothing prevents people outside the R & D of large companies to publish today. I think this comes more personal fears than lack of capacity. Just take a little care!

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Sure sir

Mohd

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Was created the mentality that only professional researchers can do research, this is completely wrong, who works in production can and should do research attention regarding the traceability and calibration of measurement equipments, systematic and accurate data acquisition are things any production professional may require of their superiors, they are factors that improve the quality of the product. This is essential in a good experimental work.

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Sometimes it will be necessary to convince the bosses that given measures are necessary, this will depend on the ability and capacity to convince the professional.

People who work in production have no researcher has data, real data on a large scale, these data conclusions without the so-called scale effect can be removed.

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Go ahead.

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I read paper again. A surface coating of say varnish, or some type of remanant of the fluid . a deposit which is very normal changed the pipe surface roughness. It is smooth. the pigging brushes imparted a new surface roughness upon the varnish. not the steel. the varnish is difficult to remove, down to the bare steel. ??

Blaine if a fluid like varnish makes the surface smooth, then the scratching by PIG brushes should increase the roughness, but i m getting reduced roughness after PIGGING. Anyhow, i m too delighted to share so much technical knowledge from you people, n i feel motivated now to get into serious research.. thanks Blaine, Rogerio and all the contributors..