GN 012.2 - Actinic Degradation and Cracking in Polythene/Nylon Coupling
- Details
- Category: Use & In-Service Inspection
| APEK - AICIP GUIDANCE NOTE |
SIGNS OR INDICATIONS IN IN-SERVICE ACTINIC DEGRADATION AND CRACKING IN POLYTHENE/NYLON COUPLING |
APEK GN 012.2 Case 2 |
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1 Figure |
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2 PE involved |
Cold water pressure piping supply system P = 1MPa, T = 20oC
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3 Sign(s) |
Circumferential crack with slight rust stain at stress concentration
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4 When & where occurred |
2009; hose coupling age 18 years; after 1000 full pressure cycles. In laundry in DN 15 in polythene/nylon hose coupling at stress raiser (thread) under tightening up tensile stress on side facing window and occasional sun for 5% of total life
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5 Detection & Investigation |
Leakage on floor by VT – then crack by VT |
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6 Failure mode(s) (damage mechanisms) |
Actinic degradation and cracking and fatigue |
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7 Most probable causes |
Long term exposure to sun, continuous tensile stress due to tightening, no blocking of pigment in plastic
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8 Outcome |
Concern until leak located; then replaced coupling; saved service fee |
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9 Possible Prevention |
Don’t expose to sun; add pigment to coupling
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10 Reference |
Compare with diesel hose failure in HMAS Westralia (4 deaths)
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SA