PIPELINE INTOLERANCE TO PIGGIING IOPF 2010 - 7001

1. 1 PIPELINE INTOLERANCE TO PIGGIING IOPF 2010 - 7001 Leo Aldeen

2. 2 Acknowledgments I would like to thank my wife, Dr. Susan Aldeen, for her support and assistance throughout the preparation of this paper. I would also like to express my thanks to INTECSEA Inc for affording me the opportunity to present this paper to the IOPF. My appreciation also goes to Dr. Dave Agerton for his encouragement.

3. 3 PIPELINE INTOLERANCE TO PIGGING Risks arise when the internal condition of a pipeline is unknown Paradoxically - we theorize: -What’s inside? -How do we know it exists? -What are we going to do about it?

4. 4 PIPELINE INTOLERANCE TO PIGGINGINTRODUCTION Pigs are not good at multi-tasking They can only perform efficiently one task at a time

5. 5 PIPELINE INTOLERANCE TO PIGGING Optimal performance of Pigs can only be realized in a narrow band of operational conditions Conditions are mainly related to ID and geometry of pipeline components Design tolerances significantly impact the size of internal bore

6. 6 PIPELINE INTOLERANCE TO PIGGING When design, construction, and installation tolerances are all combined, they make pigging more difficult Being able to use off-the-shelf pigs is substantially reduced and specially designed pigs become a necessity

7. 7 PIPELINE INTOLERANCE TO PIGGING All applicable codes and regulations are strictly followed in Pipeline Design Pipeline ID is primarily determined by: - Flow Rates - Offshore Installation Feasibility

8. 8 PIPELINE INTOLERANCE TO PIGGING Account is rarely taken of design impact on pigging. Most design constraints are cost driven Examples: -Add increased W.T. to ID -Tie several lines through Wyes

9. 9 Traversal across wye

10. 10 PIPELINE INTOLERANCE TO PIGGING

11. 11 PIG SELECTION AND DESIGN Not every pipeline engineer needs to be an expert on pigs and pigging. An appreciation of what pigs can and cannot do is essential to safely operate and maintain pipelines When quality of performance is the requirement – better pigs are needed

12. 12 PIGGING STANDARDS AND TOLERANCES Certain operators have established “de facto standards” for their pipeline pigging and maintenance they found applicable to their system. They keep good discipline in using these standards. This is not a bad thing, as more often than not, every pipeline has its own operating conditions and limitations, so “one size fits all” idea is not applicable. The drawback is that the operational knowledge is not shared, not even within the same organization.

13. 13 PIGGING STANDARDS AND TOLERANCES As far as specifications for pigging are concerned, they are either non-existent or inadequate The specification can be misleading and in some circumstances inaccurate This leads to misinterpretation and confusion.

14. 14 PIGGING STANDARDS AND TOLERANCES ASME B31.8 section A847.7 regarding ovality states “Testing for buckles, dents, and other diameter restrictions… Pipe having excessive deformation which affects the serviceability of the pipeline facilities shall be repaired or replaced. Consideration should also be given to repairing excessive ovality which may interfere with pigging operation or internal inspection.”

15. 15 PIGGING STANDARDS AND TOLERANCES For pipeline gauging, DNV OS F101, 2007, Section 408 has two standards for the size of the gauging plate, which are: 95% of nominal ID = 19.830” 97% of minimum ID = 19.196” Example: OD of 22”, maximum OD of 22.134” (including diameter tolerance) & minimum ID of 20.293” (including wall thickness tolerance) Then using 3% ovality + weld bead tolerance will give a minimum ID of 19.789” This leads to confusion as the diameter of the gauging plates differs by 0.635”

16. 16 PIGGING STANDARDS AND TOLERANCES Pigging Mechanics are not well understood and ideas are generally not based on scientific evidence Example: API RP 1110, Section 6.2 on Line Filling and Cleaning suggests a minimum pigging speed of 2 to 3 mph Arbitrary Speed – no account for ID, friction factor, pressure or pig type

17. 17 PIGGING STANDARDS AND TOLERANCES Engineering principles need to be established for the mechanics of pigging The empirical approach currently being followed is useful but totally inadequate for demanding applications

18. 18 PPSA PIG FACTOR - K Pigging Products and Service Association K factor to calculate differential pressure to drive a pig through a pipeline: DP (bars) = K / Nom’l dia. (ins.) where: K = Pig factor (number assigned to a specific pig) DP = Differential pressure in bars Nom’l dia. = Nominal diameter in inches

19. 19 PPSA PIG FACTOR - K The K factor is an arbitrary number Although this is a useful figure of merit, in engineering terms it lacks accuracy, consistency of units, and relevance to operational conditions. Just knowing an approximate driving pressure does not provide any indication of how well a pig will perform.

20. 20 PIPELINE INTOLERANCE TO PIGGING An engineering formula to provide a more meaningful measure or a dimensionless number for pig characteristics in terms of flow conditions. Modify head loss formula in terms of pressure of a fluid in motion p = ?gh

21. 21 PIPELINE INTOLERANCE TO PIGGING Re-arrange the head loss formula, replace head loss, h, with the diameter D: P = p / ?gD, where: P = Pig factor (dimensionless) p = pressure ? = flow density g = gravitational acceleration D = Inside diameter of the pipeline

22. 22 PIPELINE INTOLERANCE TO PIGGING

23. 23 PIPELINE INTOLERANCE TO PIGGING Refine P factor formula to account for all of the following parameters: ID of pipeline & Friction factor Flow rate , Flow density & Flow viscosity Differential pressure & Operating temperature Pipeline length Pipeline Internal Condition Factor Type of Pig & Pig Function

24. 24 CONCLUSION To pig or not to pig is no longer a question; it is essential for maintaining the efficiency and integrity of a pipeline. Even if a pipeline does not necessarily need to be pigged, in time it will have to be inspected to ensure that it is defect free and its corrosion treatment strategy is effective.

25. 25 CONCLUSION Pigging always carries a certain degree of risk and doing so without due diligence is probably a great deal more risky than not pigging at all The golden rule in pigging is what goes in must come out. The proviso here is that no pig should be deployed unless it will effectively perform a given function.

26. 26 CONCLUSION There is a plethora of information in the industry, but unfortunately this knowledge is not widely shared and the industry should rectify this deficiency. The aim of this paper is to improve the specifications for pipeline pigging, as well as help advance pigging technology.

27. 27 CONCLUSION The improvements are necessary to establish a set of practical engineering principles for achieving the following:

28. 28 CONCLUSION Enhanced Quality Control Protect user from faulty products Pig is fit for purpose and is the right tool for the job Determine Pig Operational Characteristics Establish Acceptance Criteria

29. 29 CONCLUSION Admittedly none of the above will be accomplished overnight, but concerted effort made by the entire industry, pig vendors and operators alike, can make it happen.