Piggability: Internal Diameter Deviation Criterion?

[DudePipeliner]

To make pipeline piggable, the internal diameter shall be somehow unique along the pipeline. the deviation , as I know, up to some 5% is acceptable for conventional pigs, while 2% is recommended for Intelligent ones.
the question is how the deviation shall be calculated? which parameters shall be accounted:

- is it only nominal wall thickness difference along the pipeline (e.g., the Zone I and Zone II differences)?

- does the wall thickness tolerances shall be considered either (e.g. 12.5% wall thickness fabrication tolerance)?

- does the OD tolerance is also in the game?

-and more important one, does the internal corrosion is also accounted? if not, what about pigging the pipeline at the end of its life?!

Pipeliner Dude
Offshore Pipeline Engineer

 

[BigInch]

ID

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[ss770640]

DudePipe,

DNV-OS-F101 Section O400 'Submarine Pipeline Design Code' stipulates equations for calculating the exact allowable ID, OD, ovality....

(to name a few.)

for the purposes of pigging, gauging or brushing operations.

Dmin,tot = Dmin(1-f0/2)-2tmax-2hbead

it incorporates weld bead and any other 'out of roundness' API driven tolerances you can throw in. (think of it as an 'absolute' minimum ID)

BEng(Hons) CEng (UK) MIMECHE