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Correlating Aldyl A and Century PE Pipe RPM Projections with Actual Field Performance

HOW LONG WILL MY OLD PE PIPE IN THE GROUND LAST?. . .

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Correlating Aldyl A and Century PE Pipe RPM Projections with Actual Field Performance

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    1. Correlating Aldyl “A” and Century PE Pipe RPM Projections with Actual Field Performance Dr. Gene Palermo P3 Consulting & Jana Laboratories Inc.

    2. HOW LONG WILL MY OLD PE PIPE IN THE GROUND LAST?

    3. DOT Advisory Bulletin ADB-02-07 Notification of the Susceptibility to Premature Brittle-Like Cracking of Older Plastic Pipe LDIW Aldyl “A” Century PE PE 3306

    4. RPM Test Procedure PPI Technical Note (TN) 16 Test specimens at multiple elevated temperatures (T) and multiple pressures (P) until slit failure occurs at time (t) Solve three-coefficient equation: Log t = A + B/T + (C log P)/T When A, B and C are known, project lifetime (t) at use temperature (T) and use pressure (P)

    5. Gas Utility A Experience Gas Utility A experienced several rock impingement failures in Aldyl “A” pipe that they installed in the early 1970’s. They also experienced some squeeze-off failures on Aldyl “A” pipe that had been properly squeezed. DuPont determined that this pipe was LDIW Aldyl “A” pipe.

    6. LDIW Aldyl “A” Pipe What is LDIW – low ductile inner wall Occurred in some Aldyl “A” pipe produced in the 1970 – 1972 era, and aka “pre-1973” Aldyl “A” pipe. Visually detectable with a reverse bend-back test Observe small cracks or crazing on the inside pipe surface

    7. LDIW Aldyl “A” Pipe

    8. RPM Testing for LDIW Aldyl “A” Pipe Internal pressure – control Squeeze-off Indented pipe to simulate rock impingement Deflected pipe Bent pipe

    9. Indented Pipe

    10. Deflected Pipe

    11. Bent Pipe

    12. Typical RPM Experiment

    14. Gas Utility A Experience/ LDIW Aldyl “A” RPM Projection Internal Pressure - Control At T = 70°F and P = 60 psig, RPM projects t = 150 yrs (5% LCL = 60 yrs) After 30 yrs in ground experience the gas utility has experienced very few slit failures due to just internal pressure.

    15. Gas Utility A Experience/ LDIW Aldyl “A” RPM Projection Indented Pipe At T = 70°F and P = 60 psig, RPM projects t = 12 yrs (5% LCL = 8 yrs) After 5 years in-ground experience the gas utility began to experience rock impingement failures that peaked after 12 years.

    16. Gas Utility B Experience Gas Utility B also kept good records for Aldyl “A” (1971-1973) vs. (1974-1984) failures for pipe, fittings and secondary loads. Some of the 1971-1973 was LDIW. They also kept records on miles of pipe installed so that they could accurately determine a leak rate per mile for each failure type.

    17. Gas Utility B Experience

    18. Gas Utility B Experience Note that the overall failure rate for 1971-1973 Aldyl “A” of 0.04 leaks per mile is an order of magnitude LESS than the leak rate for metal pipe of 0.58 leaks per mile as reported by AGA.

    19. RPM Testing for Various Generations of Aldyl “A” 1970 – 1972 1973 – 1984 1984 – 2000 LDIW Aldyl “A” Standard Aldyl “A” Improved Aldyl “A”

    21. Gas Utility B Experience/ Aldyl “A” RPM Projection

    22. Gas Utility C Experience With Century PE Pipe Gas Utility C installed Century PE 2306 pipe in the early 1970’s. By the late 1980’s the gas utility noted they were having several failures in one area, and no failures in another area. The gas utility requested RPM testing to justify leaving the “good” pipe in the ground.

    23. Gas Utility C Experience/ Century Pipe RPM Projection Internal Pressure - Control At T = 60°F and P = 60 psig, RPM projects t > 1000 yrs for both “good” and “bad” control pipe. After 15 yrs in-ground experience the gas utility had not experienced any slit failures due to just internal pressure.

    24. Gas Utility C Experience/ Century Pipe RPM Projection Indented Pipe At T = 60°F and P = 60 psig, RPM projects t = 30 yrs (5% LCL of 8 years) for “bad” indented pipe and >1000 years for “good” indented pipe. After 15 yrs in-ground experience the gas utility had experienced many rock impingement failures for “bad” pipe and no failures for “good” pipe.

    25. PSC Decision Based on these RPM projections that correlated well with Gas Utility C experience, the PSC decided to grant their request and leave the “good” Century PE pipe in service. Today, after almost 30 years in-ground service, Gas Utility C has not had any failures with that Century PE pipe.

    26. Conclusions RPM testing may be used to determine the expected life of “old generation” PE pipes in the ground - like Aldyl “A”, PE 3306 and Century Pipe. This paper showed very good correlation between RPM projections and actual field experience. RPM can determine effect of secondary loads such as indentation, deflection and squeeze-off. RPM is also useful for life projections of heat fusion fittings and butt fusion joints.

    27. The End Dr. Gene Palermo Palermo Plastics Pipe (P3) Consulting Washington, DC ¦JANA LABORATORIES Aurora, Ontario, Canada

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